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Improving the sustainability of conjugated polymer synthesis via direct arylation polymerization

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Improving the sustainability of conjugated polymer synthesis via direct arylation polymerization

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IMPROVING THE SUSTAINABILITY OF CONJUGATED POLYMER
SYNTHESIS VIA DIRECT ARYLATION POLYMERIZATION
by
Robert Mark Pankow

A Dissertation Presented to the
FACULTY OF THE USC GRAUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
CHEMISTRY

August 2020

Copyright 2020 Robert Mark Pankow
ii

Dedication

To my family and friends.

iii

Acknowledgments
I would first like to thank my family for their support and guidance throughout my life.
Specifically, to my father and sister for showing me how to keep my head up during difficult times,
and to always keep moving forward. You have both inspired me to pursue my dreams and to
accomplish goals I did not know I could achieve.
I would next like to thank my doctoral advisor, Prof. Barry C. Thompson. Without your
guidance and support none of the work in this dissertation would have been possible. You allowed
me the opportunity to to pursue many avenues of chemistry during my time here, giving me the
chance to nurture and grow my own chemical creativity. It was in your labs and through your
motiviation I was able to develop scientifically, professionally, and personally. Additionally, I
would like to thank the committee members Prof. Surya Prakash and Prof. Malancha Gupta for
agreeing to serve on my screening, qualifying examination, and defense committees.
I would next like to thank my undergraduate research advisor, Prof. R. Daniel Little, for
allowing me to work in his lab, and for instilling a sense of curiosity and wonder about chemistry
to continues to grow. You motivated me to pursue my graduate studies throguh your support and
guidance. Also, much gratitude is due to my M.S. advisor, Prof. Katsu Ogawa. I learned not only
how to grow as a chemist in your lab, but through your mentoring I learned how to grow as a
teacher, mentor, scholar, and individual. I truly cherish the memories in your labs, and I will never
forget them.
To Dr. Nemal Gobalsingham, Dr. Seyma Ekiz, and Dr. Elizabeth Melenbrink, I thank you
all for guiding me during my early years, training me in lab and on instrumentation, and helping
me through the challenging times of graduate school. Without your help my success would not
have been possible. Additionally, Nemal and Seyma, you have become great friends, and I look
iv

forward to the continued growth of our friendship. Liwei, Sanket, Pratyusha, Qingpei, Negar, Alex,
and Melanie, you have all been great colleagues and friends. Liwei, I especially owe you many
thanks since it was through your helpful discussions and hard work we were able to further push
the boundaries of DArP. I truly look forward to seeing what more you can accomplish. Sanket,
you have been an exceptional colleague and friend. Your creativity and willingness to tackle any
problem are inspirational. The work in this dissertation would not have been possible without the
assistance of the following individuals: Dr. Nemal Gobalasingham (polymer synthesis in Chapter
2), Liwei Ye (monomer synthesis, polymer synthesis, and thin-film characterization in Chapters
2-5), Neda Salami (monomer synthesis in Chapter 2), Sanket Samal (monomer synthesis
monomer synthesis in Chapter 2), and Thomas Saal (
19
F-NMR experiments in Chapter 5).
Sean, Daisy L., Ryan, Abegail, Caroline, Nick, Ashley, Antonina, Thomas, Robert, Eric,
and Narcisse, you are all wonderful friends who I was fortunate enough to meet and share many
wonderful experiences with during my time at USC. I will truly cherish all the memories, and I
look forward to staying in touch and seeing where life takes us as we grow from graduate students
to independent scientists. Additionally, Kenny, Derek, Steve, Alex, Kaveh, and Michelle, thank
you for the great friendship over these years. Daisy D., I thank you personally for being a part of
the transition from my academic to professional career, and I look forward to other moments of
life we will experience together.
To my brother Henry, I have made many journies through my life with you, from when we
were both young to throughout college. We had the blessing of watching eachother grow and being
there for eachother when things became tough or we needed a push. I appreciate all that you have
done for me, and I look forward to our continued journey. Also, sincere appreciation to Mitchell,
v

Ryan, and Addison. We have all been been fortunate enough to watch eachother grow into the
people who we are today.

vi

Table of Contents

Dedication ...................................................................................................................................... ii

Acknowledgments ........................................................................................................................ iii

List of Tables ............................................................................................................................... xii

List of Figures ............................................................................................................................. xiii

List of Schemes ......................................................................................................................... xviii

Abstract ....................................................................................................................................... xix

Chapter 1: Approaches for Improving the Sustainability of Conjugated Polymer
Synthesis using Direct Arylation Polymerization (DArP) ........................................................1

1.1 Introduction ......................................................................................................................... 1
1.2 Sustainable Solvents ............................................................................................................ 4
1.3 Cu-Catalysed DArP ............................................................................................................. 8
1.4 Oxi-DArP ........................................................................................................................... 13
1.5 Cu-Catalysed Oxi-DArP ................................................................................................... 18
1.6 Conclusions and Outlook .................................................................................................. 21
1.7 References .......................................................................................................................... 23
Chapter 2: Investigation of Green Solvents for Direct Arylation Polymerization (DArP) ...37

2.1 Introduction ....................................................................................................................... 37
2.2 Experimental ...................................................................................................................... 41
2.2.1 General procedure for PPDTBT synthesis using a high-pressure vessel ..............42
vii

2.2.2 General procedure for PPDTBT synthesis using a Schlenk-tube ......................... 43
2.2.3 General procedure for P3HT synthesis using a Schlenk-tube ............................... 43
2.3 Results and Discussion ...................................................................................................... 44
2.4 Conclusions ........................................................................................................................ 50
2.5 References .......................................................................................................................... 52
Chapter 3: Influence of an Ester Directing-Group on Defect Formation in the
Synthesis of Conjugated Polymers via Direct Arylation Polymerization (DArP) using
Sustainable Solvents.....................................................................................................................58

3.1 Introduction ....................................................................................................................... 58
3.2 Experimental ...................................................................................................................... 62
3.3 Results and Discussion ...................................................................................................... 65
3.3.1 Polymer Synthesis of PDCBT via DArP .................................................................. 65
3.3.2
1
H-NMR Characterization of DArP-PDCBT .......................................................... 70
3.4 Synthesis of PDCTT and PDCBTz via DArP ................................................................. 74
3.5 GIXRD and UV-vis Characterization of Polymer Films ............................................... 77
3.6 Conclusion .......................................................................................................................... 81
3.7 References .......................................................................................................................... 83
Chapter 4: Copper Catalyzed Synthesis of Conjugated Copolymers using
Direct Arylation Polymerization ................................................................................................95

4.1 Introduction ....................................................................................................................... 95
4.2 Results and Discussion ...................................................................................................... 98
4.3 Conclusion ........................................................................................................................ 104
viii

4.4 References ........................................................................................................................ 105
Chapter 5: Sustainable Synthesis of a Fluorinated Arylene Conjugated
Polymer via Cu-Catalyzed Direct Arylation Polymerization (DArP) ..................................111

5.1 Introduction ..................................................................................................................... 111
5.2 Results and Discussion .................................................................................................... 112
5.3 Conclusion ........................................................................................................................ 119
5.4 References ........................................................................................................................ 120
Appendix A .................................................................................................................................124

A.1 General ............................................................................................................................ 124
A.2 Polymer Synthesis ........................................................................................................... 125
A.3 Monomer NMR ............................................................................................................... 127
A.4 Polymer NMR ................................................................................................................. 133
A.5 Polymer GIXRD ............................................................................................................. 137
A.6 References ....................................................................................................................... 138
Appendix B .................................................................................................................................139

B.1. General ........................................................................................................................... 139
B.2. Monomer Synthesis ....................................................................................................... 141
Synthesis of 5-bromothiophene-3-carboxylic acid (2): ...................................................... 141
Synthesis of 2-butyloctyl-5-bromothiophene-3-carboxylate (3) ........................................ 142
Synthesis of Bis(2-butyloctyl)[2,2’-bithiophene]-4,4’-dicarboxylate (4): ......................... 142
Synthesis of Bis(2-butyloctyl)[2,2’-bithiophene]-4,4’-dicarboxylate (5): .......................... 143
ix

Synthesis of 5,5’-dibromo-2,2’-bithiophene (7): ................................................................ 144
Synthesis of 2,5-dibromothieno[3,2-b]thienothiophene (9): .............................................. 144
Synthesis of 2,2’-bithiazole (11): ....................................................................................... 145
Synthesis of 5,5’-dibromo-2,2’-dithiazole (12): ................................................................. 145
B.3.
1
H-NMR for Compounds 2-12. ..................................................................................... 147
B.4. Polymer NMR ................................................................................................................ 156
B.5. Polymer GIXRD ............................................................................................................ 161
B.6. GPC Traces .................................................................................................................... 161
B.7. References ....................................................................................................................... 162
Appendix C .................................................................................................................................163

C.1 General ............................................................................................................................ 163
C.2 Monomer Syntheses ....................................................................................................... 164
General procedure for 5-Alkyl-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione Syntheses. ... 164
5-(2-ethylhexyl)-4H-Thieno[3,4-c]pyrrole-4,6(5H)-dione (S2). ........................................ 164
5-(2-decyltetradecyl)-4H-Thieno[3,4-c]pyrrole-4,6(5H)-dione (S3).................................. 165
5-(2-octylnonyl)-4H-Thieno[3,4-c]pyrrole-4,6(5H)-dione (S4). ........................................ 165
2,5-Diiodothiophene (S6). .................................................................................................. 165
2,7-Diiodofluorene (S8). ..................................................................................................... 166
9,9-Bis(hexyl)-2,7-diiodofluorene (S9). ............................................................................. 167
9,9-Bis(octyl)-2,7-diiodofluorene (S10). ............................................................................ 167
x

1,4-bis[(2-ethylhexyloxy)]-benzene (S11). ......................................................................... 167
1,4-bis[(2-ethylhexyloxy)]-2,5-diiodobenzene (S12). ........................................................ 168
C.3. Polymer Syntheses ......................................................................................................... 169
General procedure for polymerizations. ......................................................................... 169
poly[(2,5- phenylene])-alt-(5-(2-ethylhexyl)-4H-
thieno[3,4-c]pyrrole-4,6(5H)-dione)] (P1). ........................................................................ 172

poly[(5-(2-ethylhexyl)-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione-1,3-diyl)-alt-(9,9-
dihexylfluorene-2,7-diyl)] (P2). .......................................................................................... 172

poly[(2,5-bis[(2-ethylhexyl)oxyphenylene])-alt-(5-(2-ethylhexyl)-4H-
thieno[3,4-c]pyrrole-4,6(5H)-dione)] (P3). ........................................................................ 173

poly[(5-(2-ethylhexyl)-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione-1,3-diyl)-alt-(9,9-
dihexylfluorene02,7-diyl)] (P4). ......................................................................................... 173

poly[(5-(2-ethylhexyl)-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione-1,3-diyl)-alt-(9,9-
dihexylfluorene02,7-diyl)] (P5). ......................................................................................... 174

poly[(5-(2-ethylhexyl)-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione-1,3-diyl)-alt-(9,9-
dioctylfluorene-2,7-diyl)] (P6)............................................................................................ 174

poly[(5-(2-ethylhexyl)-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione-1,3-diyl)-alt-(9,9-
dioctylfluorene-2,7-diyl)] (P7)............................................................................................ 175

C.4 Monomer NMR ............................................................................................................... 176
C.5 Polymer NMR ................................................................................................................. 193
C.6 Proposed Catalytic Cycles for Cu-DArP ...................................................................... 200
C.7 References ....................................................................................................................... 202
Appendix D .................................................................................................................................206

D.1 General ............................................................................................................................ 206
D.2 An Example of a Polymerization (Entry 10 of Table 5.1) ........................................... 207
xi

D.3 NMR of Synthesized Monomer ..................................................................................... 208
D.4 Polymer NMR ................................................................................................................. 209
D.5 GPC Traces of PDOF-OD Polymers ............................................................................ 214
D.6 Proposed End-Group Assignments ............................................................................... 215
D.7 References ....................................................................................................................... 218

xii

List of Tables
Table 1.1 Comparison of Pd and Cu with regards to abundance and cost of a typical
catalyst, including their respective ligands (phenanthroline for Cu and P(o-anisyl)3 for
Pd).
a
Concentrations obtained from reference 47.
b
Obtained from MilliporeSigma;
Catalog#: 215554 for CuI, 131377 for phenanthroline, 379875 for Pd(OAc)2, and 710563
for P(o-anisyl)3. ................................................................................................................................8

Table 2.1 Conditions explored for PPDTBT synthesis. All polymerizations used Pd2dba3
as the palladium source, P(o-anisyl)3 as the phosphine ligand, and Cs2CO3 as the base.
Concentrations were 0.4 M and performed in a high-pressure vessel unless otherwise noted.
........................................................................................................................................................44

Table 2.2 (a) Absorbance spectra for PPDTBT polymers P1-P4. (b) GIXRD patterns for
PPDTBT polymers P1-P4 ..............................................................................................................48

Table 3.1 Detailed conditions and polymerization outcomes for the synthesis of PDCBT,
PDCTT, and PDCBTz. ..................................................................................................................66

Table 3.2 GIXRD and UV-vis absorbance data for PDCBT, PDCTT, and PDCBTz.
aMeasured on polymer films prepared from a 7 mg/mL chloroform solution and annealed
at 150 °C for 30 minutes. ...............................................................................................................79

Table 4.1 Synthesis and optimization of P1 using Cu-catalyzed DArP. All reactions listed
used K2CO3 (4 equiv.) unless otherwise noted. .............................................................................98

Table 4.2 Results of the copolymerizations for the monomers depicted in Scheme 4.2,
including: molecular weights (Mn), Ð, and yield. ........................................................................102

Table 5.1 Optimization of Cu-DArP conditions for PDOF-OD. ................................................113

Table A.1 Polymer GIXRD data. ................................................................................................137

Table C.1 Synthesis and optimization of P1 using Cu-catalyzed DArP. ....................................170

xiii

List of Figures
Figure 1.1 Conventional solvents in conjugated polymer synthesis. (B) Examples of green
or sustainable solvents. (C) Sustainable solvents used in DArP. (D) Examples of
conjugated polymers prepared using DArP with sustainable solvents. ......................................... 5

Figure 1.2 (A) Examples of small-molecules synthesized via Cu-catalysed direct arylation.
(B) A plausible mechanism for Cu-catalysed direct arylation. (C) Examples of conjugated
polymers prepared using Cu-DArP. ............................................................................................... 9

Figure 1.3 (A) Examples of small-molecules synthesized via oxidative direct arylation.
(B) A plausible mechanism for oxidative direct arylation. (C) Examples of conjugated
polymers prepared using Oxi-DArP. .............................................................................................14

Figure 1.4 Depiction of different transition states for C-H functionalization for the CMD
intermediate found in DArP (left) and the Ag-mediated proton abstraction found in Oxi-
DArP (right). ..................................................................................................................................15

Figure 1.5 (A) Examples of small-molecules synthesized via Cu-catalysed oxidative direct
arylation. (B) A plausible mechanism for Oxi-CuDArP. (C) Examples of conjugated
polymers prepared using Oxi-CuDArP. .........................................................................................18

Figure 2.1 Commonly used solvents for DArP with the energy required for production
(MJ/kg) and indication of toxicity (top). Green solvents in this study tested for efficacy in
DArP (bottom). ..............................................................................................................................38

Figure 2.2 (a) Absorption profiles of PPDTBT polymers P1-P4. (b) GIXRD patterns for
PPDTBT polymers P1-P4. .............................................................................................................47

Figure 2.3 (a) Absorption spectrum of P3HT (P5) synthesized in Table 2.2. (b) GIXRD
diffraction pattern for P3HT (P5). (c) Determination of the region-regularity (RR) of P3HT
synthesized using DArP via 1H NMR spectroscopy. Collected in CDCl3 at 25 °C and 600
MHz. ..............................................................................................................................................50

Figure 3.1 1H-NMR (CDCl3, 25 °C) of PDCBT prepared via DArP using the conditions
outlined in Table 3.1: entry 4 (top), entry 7 (middle), and the Stille reference (bottom).
End-group assignments are denoted by the lowercase letters (a-n) and the major resonances
by the uppercase (A-C). For polymers prepared via DArP, acceptor-acceptor and donor-
donor homocouplings are denoted by the characters, α and δ, respectively. Resonance
labels with an asterisk (*) are not distinctly observed due to potential overlap (f* at 7.26
and c* at 7.55 ppm). All spectra referenced to CHCl3 at 7.26 ppm...............................................71

xiv

Figure 3.2 (a) Polymers (P3HT and PPDTBT) for which the DArP conditions were
optimized allowing for the exclusion of defects (α, β, and δ), allowing for the application
of these conditions to polymers with a greater potential for β-defect formation
(PPDBTTPD). (b) Depiction of the directing group effect of the ester on PDCBT forming
PDCBTβ, and the suppression or enhancement for β-defect formation when biaryls with
different β-protons (PDCTT and PDCBTz) are used compared with PDCBT. .............................73

Figure 3.3 (a) GIXRD diffraction patterns for the polymers PDCBT-Stille, PDCBT-DArP,
PDCTT, and PDCBTz. (b) Absorption profiles for the polymers PDCBT-Stille, PDCBT-
DArP, PDCTT, and PDCBTz. .......................................................................................................78

Figure 4.1
1
H NMR of P3 (top) and P4 (bottom) with sites for end-groups, acceptor-
acceptor (α), donor-donor (δ), and branching defects (β) based on homocoupled products
denoted. Conducted in CDCl3 at 25 °C. .......................................................................................103

Figure 5.1
1
H NMR of PDOF-OD synthesized using the conditions outlined in Table 5.1
(Entry 3). Collected in CDCl3 at 25 °C and 500 MHz. ................................................................117

Figure 5.2 Integral ratio between c-c’ and C-C’ protons of PDOF-OD (entry 10 of Table
5.1). Collected in CDCl3 at 25 °C and 500 MHz. ........................................................................118

Figure A.1
1
H NMR of S1 in CDCl3 at 25 °C. ...........................................................................127

Figure A.2
13
C NMR of S1 in CDCl3 at 25 °C. ..........................................................................128

Figure A.3
1
H NMR of S2 in CDCl3 at 25 °C. ...........................................................................129

Figure A.4
13
C NMR of S2 in CDCl3 at 25 °C. ..........................................................................130

Figure A.5
1
H NMR of S4 in CDCl3 at 25 °C. ...........................................................................131

Figure A.6
13
C NMR of S4 in CDCl3 at 25 °C. ..........................................................................132

Figure A.7
1
H NMR of PPDTBT (P1) in CDCl3 at 25 °C. .........................................................133

Figure A.8
1
H NMR of PPDTBT (P2) in CDCl3 at 25 °C. .........................................................134

Figure A.9
1
H NMR of PPDTBT (P3) in CDCl3 at 25 °C. .........................................................135

Figure A.10
1
H NMR of P3HT (P5) in CDCl3 at 25 °C. ............................................................136

Figure B.1
1
H NMR of compound 2 in CDCl3 at 25 °C and 400 MHz. .....................................147

Figure B.2
1
H NMR of compound 3 in CDCl3 at 25 °C and 400 MHz. .....................................148

Figure B.3
1
H-NMR of Compound 4 in CDCl3 at 25 °C and 400 MHz. ....................................149

xv

Figure B.4
1
H NMR of Compound 5 in CDCl3 at 25 °C and 400 MHz. ....................................150

Figure B.5
1
H-NMR of monomer 7 in CDCl3 at 25 °C and 400 MHz. ......................................151

Figure B.6
1
H-NMR of monomer 9 in CDCl3 at 25 °C and 400 MHz. ......................................152

Figure B.7
1
H-NMR of compound 11 in CDCl3 at 25 °C and 400 MHz. ...................................153
Figure B.8
1
H-NMR of monomer 12 in CDCl3 at 25 °C and 400 MHz. ....................................154

Figure B.9
1
H-NMR of monomer 13 in CDCl3 at 25 °C and 500 MHz. ....................................155

Figure B.10
1
H-NMR of PDCBT (Stille) collected in CDCl3 at 25 °C and 500 MHz. ..............156

Figure B.11
1
H-NMR of PDCBT prepared via DArP (entry 3 of Table 2.1). Collected in
CDCl3 at 25 °C and 500 MHz. .....................................................................................................157

Figure B.12
1
H-NMR of PDCTT (entry 6 of Table 2.1) collected in CDCl3 at 25 °C and
500 MHz. (*)Denotes potential end-group. .................................................................................158

Figure B.13
1
H-NMR of PDCBTz (entry 7 of Table 2.1) collected in CDCl3 at 25 C and
600 MHz. (*) Denotes potential end-group. ................................................................................159

Figure B.14 Expanded view of the region δ(ppm)7.75-7.55 in the
1
H-NMR spectra for
PDCBT prepared by DArP (top) and Stille (bottom). Detailing what are likely penultimate
protons for the respective DArP and Stille polymers. .................................................................160

Figure B.15 GPC traces for the synthesized polymers. ..............................................................161

Figure C.1
1
H NMR of S2 in CDCl3 at 25 °C. ...........................................................................176

Figure C.2
13
C NMR of S2 in CDCl3 at 25 °C. ..........................................................................177

Figure C.3
1
H NMR of S3 in CDCl3 at 25 °C. ...........................................................................178

Figure C.4
13
C NMR of S3 in CDCl3 at 25 °C. ..........................................................................179

Figure C.5
1
H NMR of S4 in CDCl3 at 25 °C. ...........................................................................180

Figure C.6
13
C NMR of S4 in CDCl3 at 25 °C. ..........................................................................181

Figure C.7
1
H NMR of S6 in CDCl3 at 25 °C. ...........................................................................182

Figure C.8
13
C NMR of S6 in CDCl3 at 25 °C. ..........................................................................183

Figure C.9
1
H NMR of S8 in CDCl3 at 25 °C. ...........................................................................184

xvi

Figure C.10
13
C NMR of S8 in CDCl3 at 25 °C. ........................................................................185

Figure C.11
1
H NMR of S9 in CDCl3 at 25 °C. .........................................................................186

Figure C.12
13
C NMR of S9 in CDCl3 at 25 °C. ........................................................................187

Figure C.13
1
H NMR of S10 in CDCl3 at 25 °C. .......................................................................188

Figure C.14
13
C NMR of S10 in CDCl3 at 25 °C. ......................................................................189

Figure C.15
1
H NMR of S11 in CDCl3 at 25 °C. .......................................................................190

Figure C.16
1
H NMR of S12 in CDCl3 at 25 °C. .......................................................................191

Figure C.17
13
C NMR of S12 in CDCl3 at 25 °C. ......................................................................192

Figure C.18
1
H NMR (600 MHz) of P1 in CDCl3 at 25 °C. End groups denoted with *.
Entry 8 of Table 3.1.....................................................................................................................193

Figure C.19
1
H NMR (600 MHz) of P2 in CDCl3 at 25 °C. End groups denoted with *.
Sample for P2 was 2.38 kDa synthesized using DMF since higher Mn samples were only
soluble in hot CHCl3 and DCB. ...................................................................................................194

Figure C.20
1
H NMR (600 MHz) of P3 in CDCl3 at 25 °C. End groups denoted with *.
Entry P3 of Table 3.2. .................................................................................................................195

Figure C.21
1
H NMR (600 MHz) of P4 in CDCl3 at 25 °C. End groups denoted with *.
Entry P4 of Table 3.2. .................................................................................................................196

Figure C.22
1
H NMR (600 MHz) of P5 in CDCl3 at 25 °C. End groups denoted with *.
Entry P5a of Table 3.2.................................................................................................................197

Figure C.23
1
H NMR (600 MHz) of P6 in CDCl3 at 25 °C. End groups denoted with *.
Entry P6a of Table 3.2.................................................................................................................198

Figure C.24
1
H NMR (600 MHz) of P7 in CDCl3 at 25 °C. End groups denoted with *.
Entry P7 of Table 3.2. .................................................................................................................199

Figure C.25 Proposed catalytic cycles (a) and (b) for the Cu-catalyzed DArP where the
bidentate ligand is phenanthroline. TPD is simplified as a thiophene (IIa) for clarity. ...............200

Figure D.1
1
H NMR of 9,9-bis(octyl)-2,7-diiodofluorene. Collected in CDCl3 at 25 °C and
500 MHz. Referenced to previous reports.
1
.................................................................................208

Figure D.2
1
H NMR of PDOF-OD synthesized using the conditions outlined in Table 5.1
(Entry 3). Collected in CDCl3 at 25 °C and 500 MHz. Referenced to previous reports.
2
...........209

xvii

Figure D.3
1
H NMR of PDOF-OD synthesized using the conditions outlined in Table 5.1
(Entry 10). Collected in CDCl3 at 25 °C and 500 MHz. Referenced to previous reports.
2
.........210

Figure D.4
1
H NMR of PDOF-OD synthesized using the conditions outlined in Table 5.1
(Entry 12). Collected in CDCl3 at 25 °C and 500 MHz. Referenced to previous reports.
2,3
.......211

Figure D.5
19
F NMR of PDOF-OD synthesized using the conditions outlined in Table 5.1
(Entry 3). Collected in CDCl3 at 25 °C and 470 MHz. Referenced to previous reports.
2,3
.........212
Figure D.6
19
F NMR of PDOF-OD synthesized using the conditions outlined in Table 5.1
(Entry 10). Collected in CDCl3 at 25 °C and 470 MHz. Referenced to previous reports.
2,3
.......213

Figure D.7 GPC traces of PDOF-OD polymers. .........................................................................214

Figure D.8 Proposed end-group assignments based on the model compounds S1
4
, S2
4
, S3
5
,
and S4
6
. The spectra for which all were collected in CDCl3. Colors of lettering (a-d and A-
C’) correlate to the assigned proton (Ha-Hd) on the model compound, the protons of PDOF-
OD (A-C’), and the corresponding resonances for the
1
H NMR spectrum depicted above.
The
1
H NMR spectrum is that of Entry 3 (Table 5.1), and was collected in CDCl3 at 500
MHz and 25 °C. ...........................................................................................................................215

xviii

List of Schemes
Scheme 1.1 Comparison of the number of synthetic steps and polymerization conditions
to prepare P3HET via Ox-DArP, DArP, and Stille polymerization. ............................................. 1

Scheme 2.1 Synthesis of PPDTBT from 1 and 3 using a variety of conditions listed in
Table 2.1, and synthesis of P3HT (P5) using optimized conditions listed in Table 2.3. ............ 40

Scheme 3.1 Investigation of DArP using sustainable solvents towards the synthesis of
PPDTBT (top), and the application of such solvents towards the synthesis of PDCBT,
PDCBTT, and PDCBTz (bottom). ............................................................................................... 60

Scheme 3.2 Synthesis of PDCBT via Stille (top) and PDCBT, PDCTT, and PDCBTz vi
DArP (bottom). ............................................................................................................................ 65

Scheme 3.3 Monomer synthesis. ................................................................................................. 68
Scheme 4.1 Optimization of the synthesis of P1 using Cu-catalyzed DArP. .............................. 97
Scheme 4.2 Synthesis of polymers P2-P7 using conditions derived from Table 4.1. .............. 101
Scheme 5.1 Synthesis of PDOF-OD using the conditions outlined in Table 5.1. ......................112
Scheme C.1 General synthesis for TPD monomers. ...................................................................164
Scheme C.2 Synthesis of 2,5-diiodothiophene............................................................................165
Scheme C.3 General synthesis of diiodofluorenes. .....................................................................166
Scheme C.4 Synthesis of S12. .....................................................................................................167

xix

Abstract

Improving the Sustainability of Conjugated Polymer Synthesis via Direct Arylation
Polymerization (DArP)

By
Robert M. Pankow
Doctor of Philosophy in Chemistry

Conjugated polymers are ubiquitous materials in organic electronic applications, including
organic photovoltaics (OPV), organic field-effect transistors (OFET), light-emmiting diodes
(OLED), and bioelectronic devices. The pursuit and study of conjugated polymers is largely due
to the lower-cost of synthesis, ease of device fabrication, and broader scope of applications these
materials can potentially provide in comparison to their inorganic counterparts. This presents a
class of materials that can address the environmental concerns associated with the production of
alternative energy and consumer electronic devices. Specfically, certain conjugated polymers can
be synthesized using low-cost commercial reagents at large-scale, can be solution processed
allowing for roll-toroll device fabrication, and possess desirable mechanical properties, such as
flexiblility and stretchability. However, the synthesis of conjugated polymers often proceeds via
xx

transition-metal catalysed cross-coupling reactions, which invoke the use of a transmetallating
reagent, e.g. Migita-Stille or Suzuki-Miyuara polymerizations. These methods for polymerization,
while highly efficient, require a greater number of synthetic steps and toxic, highly hazardous
reagents for the instillation of the transmetallating reagent on the monomer. Such synthetic
pathways counter the ideologies of sustainability and the minimization of environmental impact
conjugated polymers seek to address. In contrast, direct arylation polymerization (DArP) provides
conjugated polymers via C-H activation, allowing for a streamlined synthetic pathway void of
additional synthetic steps, toxic and hazardous reagents, and the generation of large amounts of
waste. Despite this, DArP still possess inherent issues regarding sustainability, such as the reaction
solvent and the transition metal catalyst. In this dissertation, strategies for improving the
sustainability of DArP are provided through the development of polymerization conditions that
replace hazardous, unsustainable solvents with relatively non-toxic, sustainable alternatives, and
conditions are developed that use more earth-abundant tranisiton metal catalysts.
In Chapter 1, an overview of sustainable condtions for DArP is detailed. This includes
describing the synthesis of various conjugated polymers using sustainable solvents with palladium
catalysts and the synthesis of conjugated polymers with more earth abundant transition metals,
such as copper. Additionally, methods such as oxidative direct arylation polymerization (Oxi-
DArP) and Cu-catalyzed Oxi-DArP are presented, which proceed without any pre-
functionalization of the monomer using a C-H/C-H dehydrogenative coupling pathway. This
chapter summaraizes and provides the background for the work detailed in Chapters 2-5.
In Chapter 2, a broad scope study of sustainable solvents is provided, including those
derived from biomass. These solvents are applied towards the synthesis of the conjugated polymer
PPDTBT, which has been shown to provide desirable properties, in applications such as OPV
xxi

devices, and possess a steramlined and straightforward monomer synthesis. From the broad scope
study, we identify a solvent, cylcopentyl methyl ether (CPME), that allows for the synthesis of
PPDTBT in good yields and with high molecular weight (Mn). To further explore the utility of the
solvent in a gerneral setting, conditions with CPME are developed for the synthesis of P3HT,
which is a conjugated polymer found in various organic electronic applications. Each of the
polymers is fully structurual characterized, and it is found that CPME allows for the defect-free
synthesis of PPDTBT and P3HT.
In Chapter 3, conditions that use CPME as a solvent are developed for the synthesis of the
conjugate polymer PDCBT. This polymer has garnered recent attention because of its relative ease
of synthesis, structural tunability, and desirable properties for applications such as polymer solar
cells. In this study, the use of directing-groups to facilitate C-H activation is also explored, since
one of the monomers for PDCBT contains ester-funcationalities that may possess directing-group
capabilities. It is found that these directing-groups are likely activating distal C-H bonds, and so
the scope of this reaction is explored to determine how the structure and electronic properties of
the coupling partner influence the polymerization outcome with regards to defect formation.
In Chapter 4, the application of more earth abundant transistion metal catalysts, such as
those containing copper, are developed. Specifically, conditions that use a Cu-phenanthroline
catalyst. The influence of the reaction solvent, base, and temperature on the polymerization
outcome is explored, and the optimal conditions are applied to range of polymer architectures. It
is found that the desired conjugated polymer structure is prepared with no obserable defects, as
evidenced through structural characterization. However, the conditions are reliant on the use of 50
mol% of catalyst, which is significantly higher than most methods for Pd-catalyzed DArP. This
xxii

however provides the first report of conjugated donor-acceptor copolymers being synthesized
using DArP with a Cu-catalyst.
In Chapter 5, the conditions developed in Chapter 4 are applied towards the synthesis of
PDOF-OD, which is a luminescent poymer noted for its potential application in OLEDs. This
polymer has been extensively studied and very well characterized, offering a nice model for
exploring the broader scope of Cu-catalysed DArP. Through the optimization of the base,
concentration, and time, the Cu-catalyst loading was lowered from 50 mol% to 5 mol%, without
significant sacrifice to Mn and yield. This presents Cu-catalysed DArP as a potentially viable
alternative to Pd-catlaysed DArP , setting the precedent for much future work within the field of
sustainable conjugated polymer synthesis.
1

Chapter 1: Approaches for Improving the Sustainability of Conjugated Polymer Synthesis
using Direct Arylation Polymerization (DArP)

1.1 Introduction
Direct Arylation Polymerization (DArP) has significantly expedited the synthesis of
conjugated polymers through the use of C-H functionalization. This has eliminated the need for a
transmetallating reagent, such as an alkylstannane used for Stille-Migita (Stille) polymerizations
or a boronic acid or ester used for Suzuki-Miyaura (Suzuki) polymerizations. In doing so,
conjugated polymers can be accessed without the need for toxic, hazardous reagents, thereby
lowering the cost and improving the sustainable aspects of their preparation. An example of such
synthetic simplification is depicted in Scheme 1.1, with the streamlined pathway for poly(3-
hexylesterthiophene) (P3HET) provided through DArP and oxidative direct arylation
polymerization (Oxi-DArP). From 1, accessing the monomer for Stille requires two separate steps
that employ pyrophoric reagents and cryogenic conditions.
1
With DArP, the monomer can be
prepared in a single step, and with Oxi-DArP P3HET can be prepared directly from 1.
2
Already,
Scheme 1.1 Comparison of the number of synthetic steps and polymerization conditions
to prepare P3HET via Ox-DArP, DArP, and Stille polymerization.
2

DArP has been used to prepare a wide-variety of conjugated polymers that have been used for
optoelectronic applications, such as polymer solar cells, light-emitting diodes, thin-film transistors,
and electrochromics.
3–8
Although still not as widely used as the aforementioned polymerization
methods of Stille and Suzuki, the increasing employment and investigation of DArP is
transforming this method into a reliable approach for conjugated polymer synthesis, rather than
just a synthetic novelty.
Initial studies regarding DArP focused on transforming methodologies for the preparation
of small-molecules via C-H activation into conditions suitable for polymerizations. For this, the
contributions of Fagnou and Gorelsky provided critical mechanistic insight.
9–12
Additionally, the
pioneering works of Ozawa, Kanbara, and Leclerc provided a starting point for DArP that could
be further expanded upon and improved.
13–15
Within this initial period of development for DArP,
our group contributed important work detailing conditions to improve the site selectivity of C-H
activation, which eliminated the occurrence of branching (β) defects, and the correlation of
structural defects with impact on polymer solar cell device performance.
16–18
These and other
studies laid the groundwork needed to determine polymerization conditions that inhibit undesired
couplings, such as homocoupling and branching defects, and allowed for the progression from
simple homopolymers to donor-acceptor copolymers, semi-random, and semi-alternating
copolymers.
18–20
Furthermore, state-of-art conditions have allowed for the ultra-low (ppm)
loadings of Pd-catalysts for certain monomers, affording polymers with high molecular weights
(Mn) and yields.
21,22
Many reviews have been published that detail various examples of the
aforementioned polymer syntheses and mechanistic studies and so they will not be discussed
here.
23–26

3

The volume of work carried out on DArP would indicate that the field has matured and the
methodology is well understood. However, this is not the case. DArP still does not possess the
scope or generality demonstrated for other polymerization methods, which is largely due to the
fact that the development of this field occurred within only the last decade. More importantly,
there are still aspects of this methodology that can be considered unsustainable. For example,
solvents used in many DArP protocols are toxic, hazardous, and require multi-step, energy
intensive routes for their production, and are not sourced from sustainable or renewable sources
(see Figure 1.1A). Another aspect, is the source of transition-metal catalyst. Up until now, DArP
protocols almost exclusively rely on palladium, where first-row transition metals could provide a
more sustainable alternative. Finally, underutilized polymerization methods, such as Oxi-DArP,
could allow for further streamlined synthetic pathways for monomer preparation, since
functionalization of the monomers with a halogen is not required. Regarding all of these aspects,
significant work has been recently accomplished, providing starting points for more sustainable
conditions to be realized. Within each of the aforementioned areas of study, our group has
contributed to pioneering polymerization conditions that set a precedent for further enhancing the
sustainable aspects of DArP.
In this mini-review, we detail the development of more sustainable conditions for
conjugated polymer synthesis via DArP and provide perspective on major underlying issues that
still need to be addressed. Given that many of the conditions used for DArP were preceded and
inspired by small-molecule synthesis, we provide some background and discussion as to how
small-molecule synthetic conditions led to the development of the corresponding polymer
syntheses, and provide general mechanistic detail in an effort to stimulate the study and discovery
of more sustainable conditions for DArP.
4

1.2 Sustainable Solvents
Although the C-H activation pathway for DArP gives the appearance that it is inherently
sustainable, there is still room for improvement. Specifically, the solvent and catalyst do not often
meet this classification. Certainly, the acutely toxic hazards, such as alkylstannanes, which are
produced in stoichiometric quantities during Stille polymerization, have been removed, but the
solvent is still a major hazard for health and the environment. As with other methods for conjugated
polymer synthesis, DArP primarily relies on a select variety of solvents that have been shown to
be proficient in solubilizing a variety of conjugated polymers, such as tetrahydrofuran (THF),
toluene, chlorobenzene (CB), and dimethylformamide (DMF), shown in Figure 1.1A. Given that
the solvent is present in the highest quantity, in comparison to any other component present in the
reaction, this presents the greatest hazard with respect to the reaction conditions. Of the
aforementioned solvents, most can be classified as reproductive toxins, carcinogens, or specifically
in the case of THF, organic peroxide formers.
27
Also, the preparation of these solvents can be
highly energy intensive making them unsustainable overall.
28
Given these factors, it can be
considered of utmost importance to identify solvents that do not require a large input of energy for
their production, can be sourced from naturally occurring feedstocks, and do not present acute
hazards to health.
29–33
Satisfying all of these parameters is challenging, although there is some
precedent from small-molecule studies employing green and sustainable solvents, with examples
shown in Figure 1.1B.
32,34–36

5

Although small-molecule direct-arylation can provide insight into conditions that can be
applied towards polymer synthesis, it is important to note that polymer synthesis often requires
substantially different conditions than their small-molecule counterparts, which often use a
stoichiometric excess of one reactant to ensure high-yields and also use high concentrations.
37

Other factors such as the solubility of the growing polymer chain, propensity for side-reactions to
occur, potentially leading to structural defects or termination of a polymer chain-end, must be
taken into account. Furthermore, polymer chains with embedded defects cannot be removed from
the desired polymer product, in contrast to molecular purifications. Thus, it is not as easy as
applying a reported small-molecule condition or substituting one solvent for another, e.g. replacing
THF with 2-MeTHF. With such factors in mind, solvents such as GVL, DEC, and EtOAc are not
generally viable solvents for conjugated polymer synthesis. GVL specifically can undergo side-
Figure 1.1 Conventional solvents in conjugated polymer synthesis. (B) Examples of green or
sustainable solvents. (C) Sustainable solvents used in DArP. (D) Examples of conjugated
polymers prepared using DArP with sustainable solvents.
6

reactions with the base, which facilitates ring-opening of the lactone.
38,39
Solvents such as DEC
and EtOAc may inhibit polymer growth due to poor solubility of the growing polymer chain, and
the boiling point of EtOAc (77 °C) is below that of many DArP protocols making this solvent only
useful for high-pressure conditions. Solubility of the polymers could be modified through the
diligent tailoring of the side-chains, to make DEC and EtOAc applicable to DArP. However, this
still limits applicability of a green solvent in a general setting. Other considerations when selecting
a solvent include solubility and stability of the catalyst and base, stability at high-temperatures,
and propensity to stabilize the intermediates present in transition-metal cross-coupling reactions.
36

With these considerations, a list of solvents (anisole, CPME, and 2-MeTHF) that may
facilitate more general application with DArP are shown in Figure 1.1C. These solvents have been
used for the synthesis of conjugated polymers via DArP, with examples shown in Figure 1.1D and
a discussion of their utility below. As general considerations for these solvents, it is important to
note the number of synthetic steps for solvent production and the stability of the solvent or its
shelf-life. For example, although capable of being derived from biomass, 2-MeTHF requires a
greater number of synthetic steps, some of which are energy intensive, for its production, and it
has been shown to be have increased organic peroxide formation with long-term storage compared
to THF.
40
In contrast, anisole and CPME can each be produced from a single synthetic step, where
anisole does not form any peroxides and it can be sourced from biomass, and CPME has been
shown to be highly resistant to peroxide formation.
34,41,42

Considering polymer examples prepared via DArP using these solvents, PBDTBT (Figure
1.1D) was prepared in high yield (96%) and good Mn (13.2 kDa) using anisole.
43
2-MeTHF has
been extensively used, following an initial report by Sommer et al.
7
Examples of polymers
prepared via DArP using this solvent include PTB7 (42.0 kDa and 88% yield) and P3HT (19.7
7

kDa and 74%), both of which are extensively used in organic electronics, particularly organic
photovoltaic (OPV) applications.
3,5

CPME has been shown to work for a variety of monomers, since its initial use in DArP by
Ozawa et al.
44
In a recent study, we probed the application of CPME, 2-MeTHF, GVL, and DEC
for the synthesis of PPDTBT (Figure 1.1D).
38
It was found that CPME provided the best Mn (41.0
kDa) and yield (78%). In subsequent studies, CPME was successfully applied towards the
synthesis of the copolymer PDCTT (26.4 kDa and 90% yield), which contains two ester
functionalities that can potentially function as directing-groups for distal protons.
45
Recent work
from our group has also shown that amide functionalized polythiophenes can be synthesized using
CPME, affording P3AAT (15.4 kDa and 77% yield) and P3AAT-NH (11.6 kDa and 63% yield).
46

With these examples we have shown that CPME is capable of being a suitable solvent in DArP for
a wide-variety of conjugated polymers, allowing for high Mn and yield to be obtained.
Future work with sustainable solvents will require their implementation in a variety of
protocols (some of which are discussed below), so as to show good tolerance for the conditions
used in polymerizations and the structural variation of monomers. Specifically, many DArP
reactions, like those described in the following sections, require highly-polar, coordinating
solvents, such as dimethylacetamide (DMA). Identifying additional sustainable solvents that can
satisfy this role and a general utility for the synthesis of a variety of conjugated polymers would
be a significant advance. Since sustainable chemistry is a rapidly advancing field, monitoring the
output and identification of new sustainable solvents that are applicable in aryl-aryl cross-coupling
reactions should lead to the discovery of new solvents compatible with DArP.
8

1.3 Cu-Catalysed DArP
Aside from the solvent, another important area of interest is replacing the Pd-catalyst with
a first-row transition metal, such as a Cu-catalyst. The concentration of copper present in the
earth’s crust is 60 g/ton (Table 1.1), which is orders of magnitude greater than that of Pd, which
is at 0.015 g/ton (Table 1.1).
47
Based of the abundance of Cu in comparison to Pd alone, it becomes
apparent that developing conditions that allow for the replacement of Pd with Cu in DArP are
imperative. From a cost-analysis standpoint, there is again added benefit to using Cu. Shown in
Table 1.1, the difference in cost per gram for CuI and Pd(OAc)2, both of which are the most
common metal sources for each, and the respective
Entry Abundance
a
Purity
b
Cost per gram
b

Pd 0.015 g/ton 99.98% (Pd(OAc)2) $146
Cu 60 g/ton 99.999% (CuI) $9
Phenanthroline

- >99% $7
P(o-anisyl)3 - >96% $43
Table 1.1 Comparison of Pd and Cu with regards to abundance and cost of a typical catalyst,
including their respective ligands (phenanthroline for Cu and P(o-anisyl)3 for Pd).
a
Concentrations
obtained from reference 47.
b
Obtained from MilliporeSigma; Catalog#: 215554 for CuI, 131377
for phenanthroline, 379875 for Pd(OAc)2, and 710563 for P(o-anisyl)3.
ligands (phenanthroline for Cu and P(o-anisyl)3 for Pd) give Cu an obvious cost advantage. To
facilitate this transition of metals, Cu-catalysed aryl-aryl cross-couplings have been studied,
serving as a precursor to the development of conditions for DArP (Cu-DArP) to be realized.
47–49

As shown with the examples of Daugulis et al., Miura et al., and You et al. provided in Figure
9

1.2A, Cu-catalysed direct arylation conditions vary greatly from those of Pd.
50–53
Many protocols,
such as those by Daugulis and You et al., employ an amine ligand, such as phenanthroline, rather
than phosphine (Figure 1.2A).
50–52
Phosphine ligands still have utility, as shown with the work by
Miura et al (Figure 1.2A), and each of the protocols provide the cross-coupled products in high-
yields (75-96%), albeit with a stoichiometric excess of one reactant in all cases.
53
Another
noticeable difference is that the conditions require generally higher temperatures (>120 °C) than
Pd-catalysed protocols, owing to the lower reactivity of the Cu-catalysts. Additionally, carboxylic
acid additives are not present with the Cu-catalyzed protocols, which are often used for Pd-
Figure 1.2 (A) Examples of small-molecules synthesized via Cu-catalysed direct arylation. (B)
A plausible mechanism for Cu-catalysed direct arylation. (C) Examples of conjugated polymers
prepared using Cu-DArP.
10

catalyzed direct arylation, since these ligands can enable the disproportionation of Cu
I
, leading to
Cu
0
and Cu
II
.
54

With regards to a potential catalytic cycle (Figure 1.2B), it is proposed that the Cu-catalyst
proceeds through Cu
I
to Cu
III
oxidation states, which is based on the work by Daugulis and
mechanistic studies by Lin.
50,51,55
It should be noted copper has access to a wide range of oxidation
states (Cu
0
-Cu
I
-Cu
II
-Cu
III
), and these may be present depending on the copper source, additives,
and substrates or monomers used.
56
Concerning the mechanism depicted in Figure 1.2B, it is
believed that the oxidative addition step is rate-limiting given the relative instability of Cu
III
.
57

Aside from the disproportionation of Cu
I
, which was mentioned above, another side-reaction that
can occur is hydrodehalogentation.
58,59
This side-reaction also occurs with Pd-catalysed
methodologies, leading to the termination of chain ends, and eliminating sources of adventitious
water may help to avoid this.
58

Despite the aforementioned challenges with adapting Cu-catalyzed direct arylation
conditions to DArP, we have recently reported pioneering studies detailing the synthesis of a
variety of conjugated polymers using conditions derived from those developed by Daugulis et al.
and You et al (shown in Figure 1.2C).
60,61
These seminal reports provide another example of how
small-molecule conditions can be meticulously transformed to allow for conjugated polymer
synthesis. Initially, we found after extensive optimization of the solvent, concentration, and base
that thieno[3,4-c]pyrrole-4,6-dione (TPD) can be copolymerized with a variety of aryl-iodide
donors using a mild base (K2CO3) and amide solvent (DMA), shown in Figure 1.2C. For example
PDHF-TPD was afforded in 10.1 kda and 55% yield, and the heterocycle thiophene was
incorporated into the copolymer PTTPD in 8.8 kDa and 30% yield (Figure 1.2C). These
conditions were reliant on 50 mol% of the Cu-phenanthroline catalyst, where lower loadings did
11

not afford optimal Mn and yield. Through
1
H-NMR experiments, we found hydrodehalogenation
as the dominant side-reaction, terminating the chain ends. We attributed the required high loadings
of catalyst and frequency of dehalogenation to a lower reactivity of the C-H bond in TPD.
Although the use of a more reactive aryl iodide was required, even for Pd-catalysed DArP, certain
condition sets have required the use of an aryl-iodide to afford satisfactory Mn and yield when
using TPD based monomers.
62
Another point of concern was that TPD contains a directing-group,
which may be an essential functionality of the monomer to allow for C-H activation. We were
therefore interested in applying these polymerization conditions to a monomer without a directing
group, in order to ensure that this methodology is not limited in scope.
As such, we focused on a class of monomers that has been used frequently to test the
efficacy of various DArP condition sets, which are the polyflourinated arenes, such as
tetrafluorbenzene and octofluorobiphenyl.
8,44,63
These monomers are commercially available, can
be incorporated into conjugated polymers with high Mn and yields, and provide access to a highly-
reactive C-H bond without any directing groups. Because of the high-temperatures required for
Cu-DArP, we chose octafluorobiphenyl as the ideal monomer for study. We found that with
optimization of the polymerization conditions (increasing concentration and changing the base
from K2CO3 to K3PO4) for PDOF-OD (Figure 1.2C), we could lower the loading of the CuI-
phenanthroline catalyst from 50 to 5 mol%, yielding a polymer of 16.4 kDa in 54% yield. This
result shows the utility of Cu-DArP towards the replacement of conventional Pd-catalysts, since a
C-H bond was functionalized without the use of a directing-group.
A lingering issue from these initial studies is the employment of aryl-iodides, which require
aggressive reaction conditions for their synthesis and exhibit lower stability.
61,64–66
Since aryl-
bromides have allowed for the cross-coupled product via Cu-catalysed small-molecule direct
12

arylation (Figure 1.2A), we envisioned that these conditions could be optimized to facilitate
polymer synthesis. Indeed, by using a mixed solvent system with DMA/m-xylene we were able to
obtain the desired conjugated polymers using aryl-bromides.
67
Examples, shown in Figure 1.2C,
include PDHF-TPD (10.4 kDa and 72% yield), PDOF-OD (17.3 kDa and 54% yield), and PTTPD
(6.4 kDa and 65% yield). In the case of PDHF-TPD and PDOF-OD, the Mn and yields are similar
to those prepared using aryl iodides. To explain the dependence of the solvent, e.g. a mixture of
DMA and m-xylene, computational studies by Lin indicate two potential, distinct mechanistic
pathways for Cu-catalysed arylations, where one pathway is categorized as anionic and one is
characterized as neutral. For the neutral pathway, a non-polar solvent, such as m-xylene, is
preferred, and so it is likely that the Cu-catalysed polymerization with aryl bromides proceeds via
the neutral pathway.
55
This study by our group provides a missing critical piece in identifying Cu-
DArP conditions that provide an equivalent outcome to Pd-DArP.
It should be noted that aryl-chlorides have been used in DArP with Cu-catalysts, although
these required a Pd-catalyst as well.
68
In the report by Kanbara et al., the Cu-catalyst is proposed
to operate as a binary catalytic system with Pd, assisting with the deprotonation and
transmetallation of the C-H functionalized monomer.
The amount of future work and potential for Cu-DArP is vast, given that this methodology
is not as developed as Pd-DArP, and optimization of the polymerization conditions is critical for
further expansion of this methodology. Major areas of focus should be on using more sustainable
solvents, and optimizing Cu-catalysts via ligand design or through the use of additives to help
facilitate C-H activation and stabilize CuIII-species after oxidative addition.
13

1.4 Oxi-DArP
Oxidative direct arylation, also referred to as dehydrogenative direct arylation, is a
straightforward and efficient method for the synthesis of biaryl compounds. It is distinct from
conventional direct arylation in that the substrates or monomers used do not require any
functionalization, such as the installation of a halogen required for C-H/C-X cross coupling
reactions, since the reaction proceeds through an oxidative C-H/C-H coupling pathway.
69–71
This
simplifies the synthesis of monomers even more, allowing for rapid access and shorter synthetic
pathways, thereby enhancing the overall sustainability.
The development of this methodology towards the preparation of conjugated polymers is
again reliant on the precedent of small-molecule studies, depicted in Figure 1.3A. The seminal
work by Mori et al. (Figure 1.3A) described the homocoupling of thiophenes functionalized with
a bromine, affording the desired bithiophene product in 77% yield.
72
The conditions included
PdCl2(PhCN)2 as a catalyst and AgF as the terminal oxidant. Comparing to other direct arylation
methodologies, this one is intriguing because it is done at room temperature and the C-H/C-H
coupling is selective over the C-H/C-Br coupling, the latter of which occurs with most direct
arylation protocols. This initial condition set was improved upon by the works Zhang and Shi.
73,74

Each describe the use of a Pd(OAc)2 catalyst, Ag2CO3 as the terminal oxidant, and acetic acid as
an additive. The conditions of Shi et al. differ mainly in the choice of solvent, where they chose
benzene and were required to use diisopropyl sulphide in order to avoid the precipitation of Pd-
black.
74

As depicted in the works of Zhang and Shi, shown in Figure 1.3A, achieving a high-level
of selectivity for the cross-coupled product, through the activation of only C-H bonds, is reliant on
the selectivity of distinct C-H bonds at the two different points of proton abstraction and metalation
14

during the plausible catalytic cycle, shown in Figure 1.3B.
70
Specifically, after metalation of the
first aryl substrate, the corresponding complex must react with the second substrate selectively. It
should be noted that the catalytic cycle for this reaction is subject to the conditions employed,
namely the choice of oxidant, catalyst, and monomer, given that Pd
II
-Pd
IV
catalytic cycles are
possible in place of the Pd
0
-Pd
II
cycle presented.
71
In such a cycle, the Pd-catalyst is oxidized
before the C-H activation step, rather than after reductive elimination, differing from what is
shown in Figure 1.3B. It is likely that selection of electronically distinct cross-coupling partners,
such as those selected by Zhang and Shi et al., help to ensure a high selectivity of the cross-coupled
rather than homocoupled product. It should be noted that conditions with Ag-based terminal
Figure 1.3 (A) Examples of small-molecules synthesized via oxidative direct arylation. (B) A
plausible mechanism for oxidative direct arylation. (C) Examples of conjugated polymers
prepared using Oxi-DArP.
15

oxidants are shown simply because they were employed in the initial reports, but many oxidants
can be used, such as molecular oxygen, K2S2O8, oxone, and Cu(OAc)2 (Figure 1.3B).
69,70

However, in the case of Ag-based oxidants, a study by Sanford et al. has described a more
intimate role of the Ag-oxidant rather than serving as simply a terminal oxidant for the Pd-
catalyst.
75
Specifically, the Ag-cation may be participating in the C-H activation step facilitating
metalation of the monomer to the Pd-catalyst. Such reactivity is found to occur most prevalently
with Ag-carboxylates, which can in principle be generated in situ with the addition of a carboxylic
acid additive, or the silver-carboxylates can be easily prepared and isolated. This difference in
mechanistic pathway is depicted in Figure 1.4, with the conventional CMD pathway on the left
and the intermediate for the Ag-mediated pathway on the right. In addition, evidence for a
bimetallic pathway (C-H activation at two separate Pd
II
centers followed by transmetallation) has
been shown by Stahl et al., in contrast to the monometallic mechanism shown (Figure 1.3B).
76

Concerning the polymerization, oxidative direct arylation polymerization (Oxi-DArP) has been
gaining interest with numerous studies using conditions derived from the initial small-molecule
studies of Mori, Shi, and Zhang, which employ a Pd-catalyst with Ag-oxidant. Early work focused
on the development of conditions that could afford homopolymers so as to provide a proof-of-
Figure 1.4 Depiction of different transition states for C-H functionalization for the CMD
intermediate found in DArP (left) and the Ag-mediated proton abstraction found in Oxi-DArP
(right).
16

concept that the small-molecule conditions can be applied to a polymerization, but were very
limited in scope.
77,78
Additionally, the potential for this methodology to simplify conjugated
polymer synthesis had not yet been realized since the monomers studied required very specific
structural functionalities adding additional steps to the syntheses. To overcome this limitation, we
developed conditions that allow for the polymerization of an unsymmetrical monomer (1)
(Scheme 1.1). In comparison, preparation of the monomer for Stille-P3HET requires an extended
synthesis containing multiple steps that used hazardous reagents and cryogenic conditions,
depicted in Scheme 1.1.
1,2
From our initial report, we were able to optimize conditions to afford
P3HET in 11.7 kDa and 68% yield with a regioregularity (rr) of 89% (Figure 1.3C).
79
In a
subsequent study, Chen et al. applied similar conditions toward the synthesis of P3OST (9.6 kDa
and 98% yield) with a reported rr of 99% (Figure 1.3C).
2,80
This validates Oxi-DArP as a method
that with further development could rival conventional DArP.
80
The underlying mechanism
influencing rr is the ability of the carbonyl (in the case of P3HET) or the sulfone (in the case of
P3OST) to function as a directing group, allowing for the site-selective activation of the
neighbouring C-H bond.
23
The preparation of PProDOT, described by Reynolds et al., is
particularly interesting because it shows that Oxi-DArP methodologies can be tuned to allow for
the activation of electron-rich monomers without any directing-groups, which can be found with
the carboxylate of P3HET or the sulfone of P3OST (Figure 1.3C).
81
Sommer et al. has also
achieved homopolymerizations of an electron rich indacenodithiophene monomer, showing utility
for Oxi-DArP with different electron-rich monomers commonly used for organic electronic
applications.
82
Cu(OAc)2 can also be employed as an oxidant with Pd-catalysed Oxi-DArP, which
was reported in the aforementioned study by Sommer et al. and for PBTzP (8.8 kDa and 93%
yield) by You et al., depicted in Figure 1.3C.
82,83
It should be noted that many of these protocols
17

are reliant on an excess of oxidant, which, in the case of Ag-based oxidants specifically, diminishes
the overall sustainability of the polymerization conditions.
The utility of this method for copolymer synthesis is shown in Figure 1.3C. We reported
the synthesis of the random copolymers P3HET-TPD-5% (13.9 kDa and 54% yield) and P3HET-
BTz-5% (11.7 kDa and 68% yield).
79
Perfectly alternating donor-acceptor copolymers have also
been prepared, such as PBT-OF (23.2 kDa and 66%) by Kanbara et al. and PBST-BDT (13.6 kDa
and 83% yield) by Chen et al.
63,80
The synthesis of PBT-OF by Kanbara is of particular interest
because they were able to use a sub-stoichiometric amount of Ag-oxidant (0.5 equivalents).
Significant progress has been achieved for Oxi-DArP, with polymerization conditions
affording homopolymers prepared from an unsymmetrical monomer with high-levels of
regioregularity and copolymers with minimized homocoupling defects. The aforementioned work
validates this method as a tool for simplifying the synthesis of conjugated polymers, and it
promotes sustainability by reducing the number of synthetic steps and the associated waste for
monomer preparation. Given all this, there are still areas where Oxi-DArP can be improved.
Namely, the monomer scope remains rather limited, since clear correlations between the monomer
structure, catalyst, and oxidant are not known. Additionally, it is challenging to determine if an
oxidant and catalyst will provide any polymer product a priori, where with DArP many condition
sets have been shown to work with a broad scope of monomers. Also, more importantly with
regards to sustainability, many Oxi-DArP protocols require using stoichiometric amounts of silver-
oxidants, often Ag2CO3. Thus, identifying more sustainable oxidants or finding more general
conditions for known oxidants, such as molecular oxygen and Cu(OAc)2, is important. In a more
practical sense, the use of this methodology to synthesize functional materials with proven utility
in organic electronic applications equivalent to that of conventional polymerization methods has
18

not been realized. This may remain a major challenge however, since the performance conjugated
polymers is often sensitive to oxidants, such as molecular oxygen, which can lead to defects in the
structure and therefore compromise performance for a given application.
84

1.5 Cu-Catalysed Oxi-DArP
A methodology combining the sustainable aspects of Oxi-DArP and Cu-DArP is Cu-
catalysed Oxi-DArP, which is depicted in Figure 1.5. This synthetic method proceeds through
dehydrogenative or oxidative direct arylation, where a C-H/C-H cross coupling occurs, using a
copper catalyst.
69,70,85
The monomers do not require functionalization, and so the number of
synthetic steps and associated workup and purification becomes simplified. As with Cu-DArP, the
use of a copper catalyst provides another aspect of sustainability and low-cost to this synthetic
method.
Figure 1.5 (A) Examples of small-molecules synthesized via Cu-catalysed oxidative direct
arylation. (B) A plausible mechanism for Oxi-CuDArP. (C) Examples of conjugated polymers
prepared using Oxi-CuDArP.
19

Shown in Figure 1.5A, the pioneering work of Miura et al. paved the way for Cu-catalysed
Oxi-DArP.
86
The conditions described used an excess of Cu(OAc)2 with a carboxylic acid additive
(PivOH) to afford the cross-coupled products of various 2-arylazines and azoles. Although the
amount of Cu(OAc)2 needed seems excessive (2.5 eq.), it should be noted that Cu(OAc)2 is
functioning as a single-source for a catalyst and oxidant. No other oxidants are employed, and in
comparison typical procedures for Pd-catalysed Oxi-DArP require a Pd-catalyst and an oxidant,
such as Ag2CO3 or Cu(OAc)2, in similar quantities.
Following up on the initial findings of Miura et al., Daugulis et al. reported a
dehydrogenative cross-coupling using a CuI/phenanthroline catalysed system with molecular
iodine as the oxidant (Figure 1.5A).
50
They concluded that the iodine iodinates one of the
substrates, presumably the electron-rich one, which then undergoes Cu-catalysed cross-coupling
as described in Figure 1.2B. Given that one of the monomers becomes iodinated in situ, the cross-
coupling likely proceeds through the mechanistic pathway described in Figure 1.2B rather than
that of Figure 1.5B. However, it provides useful conditions for achieving dehydrogenative cross-
coupling using a CuI-catalyst, and their study showed a comprehensive scope for the methodology,
affording cross-coupled products in good yields and with high regioselectivity.
In the report by You et al., dehydrogenative cross-coupling was shown to occur with good
chemoselectivity, affording the bromine-functionalized azole in good yield (69%), which is shown
in Figure 1.5A.
87
The conditions required only a sub-stoichiometric amount (0.5 eq.) of Ag2CO3
as an additional terminal oxidant, since molecular oxygen was also employed, showing that such
a synthetic transformation can occur with the simplest and most sustainable of oxidants.
Given that the identity of transition-metal catalyst has changed when compared to Oxi-
DArP, there are major differences and considerations to be made with regards to the mechanism
20

of Cu-catalysed dehydrogenative cross coupling (Figure 1.5B), which can have profound effects
when selecting monomers to employ for this methodology. The proposed cycle proceeds through
a Cu
II
-Cu
III
-Cu
I
cycle containing two separate oxidations, one before reductive elimination and
one after, of the Cu-catalyst (Figure 1.5B).
70,85
This differs greatly from Pd-catalyzed Oxi-DArP,
where oxidation of the catalyst is proposed as occurring after reductive elimination (Figure 1.3B).
Also, aza-heterocycles, e.g. imidazole, thiazole, and oxazole, are often used because of the
coordinative ability of the nitrogen in the heterocycle to a metal-center, such as copper, to further
enhance the acidity and reactivity of the adjacent C-H bond, thereby lowering the energy needed
for proton abstraction and functionalization.
88
This structural feature can also be seen with the
representative polymers in Figure 1.5C.
Compared to the other methodologies described, the number of polymers prepared via Cu-
catalysed Oxi-DArP is limited, which is due to the fact that this is a more emergent methodology
for conjugated polymer synthesis. Shown in Figure 5C, You et al. reported the synthesis of a
variety of biimidazole functionalized homopolymers, such as PBDI-18 (44.5 kDa and 85% yield),
using 20 mol% Cu(OAc)2, sub-stoichiometric quantities of Ag2CO3 (0.5 equiv), and with
molecular oxygen as an additional oxidant.
89
Kanbara et al. prepared the polymers PDEFBTz (19.8
kDa and 98% yield) and PBTBTz (5.1 kDa and 73% yield) using 10 mol% Cu(OAc) 2 and under
air (where molecular oxygen serves as the oxidant).
90
The polymers synthesized in Kanbara’s
study were also evaluated for practical applications through the fabrication of OFET and OLED
devices, demonstrating the effectiveness of this methodology for the preparation of functional
polymers.
Given the relative infancy of this Cu-catalysed Oxi-DArP, there is much work to be done
related to the optimization of conditions and improvement of sustainability. Discovering new Cu-
21

catalysts, ligands, and additives may help improve the polymerization outcome. Additionally,
finding sustainable solvents that can achieve the high-temperatures required for the
dehydrogenative coupling to occur without inducing side-reactions is critical for enhancing the
sustainable aspects of this method. Since this method for polymerization has been primarily used
for aza-heterocylces, discovering conditions that tolerate monomers more frequently employed for
organic electronic applications, such as thiophenes, is imperative.
1.6 Conclusions and Outlook
Strategies for improving the sustainability of DArP have been presented, including using
sustainable solvents, Cu-DArP, Oxi-DArP, and Cu-catalysed Oxi-DArP. As discussed in this mini-
review, DArP can be considered inherently sustainable when compared to other polymerizations,
e.g. Stille or Suzuki, but by changing the solvent, catalyst, or method of polymerization to more
sustainable alternatives, the sustainability of DArP can be further improved. With numerous small-
molecule studies performed that address these points, the greatest challenge becomes applying and
optimizing these conditions towards conjugated polymer synthesis.
A central theme or strategy for improving sustainability for any polymerization method is
by employing a solvent sourced from a renewable resource or one that can be produced with
relative simplicity and without presenting hazards to health and the environment. The sustainable
solvents anisole, CPME, and 2-MeTHF have been used for the synthesis of a variety of polymers
via DArP, and their application for future study should be considered. Our group has developed
and optimized conditions for CPME, and this solvent offers great appeal as a general solvent for
DArP.
Also, the source of the transition-metal, which is typically Pd, for the DArP catalyst must
be considered, and developing catalysts that incorporate first-row transition metals, such as copper,
22

is imperative. While Cu-DArP does not have as broad of scope as its Pd-catalysed counterpart, it
is important to note that the extent of study and availability of pre-catalysts are far from complete.
Towards this end, we have contributed multiple studies showing that Cu can be used in catalytic
quantities (5 mol% loading) targeting a variety of conjugated polymer architectures. Fine-tuning
the conditions through optimization of the pre-catalyst, ligand, solvent, and base (as has been done
with Pd-catalyzed DArP over the last decade) will facilitate the discovery of more general
conditions.
Additionally, developing conditions that allow for a broader monomer scope for Oxi-
DArP, both Pd and Cu-catalysed, will enhance the utility of each of these synthetic methods. The
potential for Oxi-DArP to become the most sustainable method for conjugated polymer synthesis
is apparent. However, it currently suffers from requiring unsustainable solvents, such as DMA,
and precious metal oxidants, such as Ag2CO3, which are often present in stoichiometric or excess
quantities. The development of conditions that address all of these points will be challenging, but
given the broad application of conjugated polymers the appeal of such an enabling advancement
is significant.

23

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37

Chapter 2: Investigation of Green Solvents for Direct Arylation Polymerization (DArP)

2.1 Introduction
Conjugated polymers have definitively shown their potential as alternative materials to
inorganic based semiconductors, which can have costly syntheses or contain highly toxic
constituents, for applications including photovoltaics (PV), thin-film transistors (TFT), light-
emitting diodes (LED), chemical sensors, and for biomedical applications.
1–6
The most desirable
feature of conjugated polymers, in part, lies in that their syntheses and purification steps do not
contain toxic materials, costly steps that inhibit scalability, or overall lengthy routes compromised
of numerous steps with each requiring purification. Unfortunately, the efforts to obtain high-
performance, such as power conversion efficiency (PCE) in the case of PV applications, have
seemingly clouded the focus of the field.
7
Rather than pursuing conjugated polymer targets that
may offer a streamlined, low-cost synthetic pathway along with high-performance, the polymers
pursued require numerous synthetic steps to yield the desired monomers. Likewise, of the
numerous transition metal catalyzed polycondensations, such as Stille, Suzuki, or Negishi, most
require the implementation of cryogenic conditions, pyrophoric reagents, and the use of toxic,
heavy-metals. Seemingly, it appears as if the original focus of conjugated polymers as
environmentally benign alternatives to inorganic semiconductors has become side-lined with
efforts to prepare the monomers and subsequent polymers in an environmentally focused manner.
To contrast with most of the transition catalyzed polymerizations widely employed, direct
arylation polymerization (DArP) has become a successful method for the preparation of
conjugated polymers, which circumvents the necessity for cryogenic conditions, pyrophoric
reagents, and toxic tin byproducts.
8–13
This methodology has even been incorporated into
38

continuous flow systems allowing for large-scale preparation of conjugated polymers in a safe,
effective, and reproducible manner.
14,15
However, to firmly establish DArP as the most
environmentally benign pathway for conjugated polymer synthesis, the conditions themselves
need to be assessed and more environmentally benign alternatives for solvents and additives
replace current reagents. Regarding this point, very little has been done. Many of the solvents used
for DArP require energy intensive processes for their synthesis and purification, shown in Figure
2.1 with xylenes, toluene, THF, DMF, and DMA, with all of those solvents possessing a high level
of toxicity. To our knowledge, there are only a few examples of the implementation of green
solvents in DArP. Illustrated in Figure 2.1, Sommer et al. introduced methyltetrahydrofuran
(MeTHF) as a solvent, which was then used by Marks et al.
16,17
Also, Leclerc et al. showed that
water with the addition of a phase-transfer agent can be incorporated into the reaction, but requires
the presence of an organic co-solvent, such as toluene.
18
Ozawa et al. employed cyclopentylmethyl
ether (CPME) for DArP, but did not obtain optimal results and this solvent and the conditions for
it to provide optimal results (high Mn and good yield) have remained unfound, to our knowledge.
19

Conversely, there has been extensive study regarding the role of environmentally benign,
green solvents for small-molecule direct arylation, but likely do to foreseen challenges in terms of
polymer solubility there has been little application of such solvents to conjugated polymer
Figure 2.1 Commonly used solvents for DArP with the energy required for production (MJ/kg)
and indication of toxicity (top). Green solvents in this study tested for efficacy in DArP (bottom).
39

synthesis.
20–23
Solvents studied for biaryl compounds and the other small-molecule compounds
include: ethyl acetate and water mixtures, carbonates, and cyclopentyl methyl ether (CPME).
22–24

Because of this apparent lack of research and focus, we felt compelled to study solvents and
additives that can be considered more environmentally benign than those widely used, such as the
ones listed in Figure 2.1. Solvents would be selected based on whether they can be considered
renewable resources or they require less processing and refinement.
25,26
Interest in this study is
further supported with the numerous applications of green solvents to small molecule direct
arylation.
A green solvent that presents itself as a suitable replacement for the common solvents
employed for conjugated polymer syntheses is CPME.
19
In comparison to many ethereal solvents,
including MeTHF, CPME provides several merits furthering DArP’s environmental
compatability.
24,27
For example, it can be manufactured by the addition of methanol to
cyclopentene in a waste-free process. It also has a high hydrophobicity allowing for ease of water
removal, a low-level of peroxide formation, a high stability under acidic/basic conditions, and a
narrow explosion range.
A conjugated polymer that coincides with the tenets of green chemistry is pol[2,5-
bis(2hexyldecyloxy)phenylene-alt-(4,7-dithiophen-2-yl)benzo[c][1,2,5]thiazole)] (PPDTBT) ,
shown in Scheme 2.1.
28
This polymer can be easily prepared in only a few steps from
commercially available reagents, and has shown great promise for solar-cell applications with a
power conversion efficiency (PCE) of 3.25% in large-area, roll-to-roll (R2R) processed devices.
14

It offers a stark contrast to many of the high-performing conjugated polymers currently being
studied for PV applications, which require stringent, air and moisture free processing conditions
and toxic additives to achieve high-efficiency in only small-area solar cell devices. Thus, PPDTBT
40

is the perfect candidate for study in regards to applying green solvents to DArP reaction conditions.
Another polymer that shares these attributes is poly(3-hexylthiophene) (P3HT), shown in Scheme
2.1. P3HT has shown great promise in numerous applications outside of PV, making it an
ubiquitous material for the organic electronic community. Also, P3HT has been well characterized
spectroscopically allowing for a direct analysis for branching (β) defects.
Herein, we report the synthesis and optimization of PPDTBT using the green solvent
CPME, MeTHF, GVL, and DEC. Other carboxylate additives other than neodecanoic acid (NDA)
are also explored, including the industrially relevant napthenic acid (NPA) and bismuth
neodecanoate (BiNDA). We found that CPME provided optimum results affording PPDTBT with
a Mn of 41 kDa and a yield of 78%, vastly improving upon the high-pressure THF conditions
previously reported (15 kDa and 78%).
28
Application of CPME towards the synthesis of P3HT via
DArP was then performed, affording a polymer product with 93% regio-regularity (RR), a Mn of
12 kDa, and no detected β-defects. We believe based on these results CPME has the greatest
potential to overtake the common, hazardous solvents employed for DArP, allowing DArP to
become a truly competitive alternative for conventional conjugated polymer synthetic methods in
Scheme 2.1 Synthesis of PPDTBT from 1 and 3 using a variety of conditions listed in
Table 2.1, and synthesis of P3HT (P5) using optimized conditions listed in Table 2.3.
41

both small-scale and industrial settings. Structural analysis for the polymers was performed using
1H NMR spectroscopy, absorbance spectroscopy, and GIXRD for which all information is
provided in Appendix B.
2.2 Experimental
All reactions were performed under dry N2 in oven dried glassware, unless otherwise noted.
Unless otherwise noted, all reagents were purchased and used as received from commercial
sources. Solvents were purchased from VWR and used without purification, unless otherwise
noted. Anhydrous, unstabilized cyclopentyl methyl ether (CPME) was purchased and used as
received. Cs2CO3 was ground into a fine powder and dried at 120 °C in a vacuum oven before use.
Tetrahydrofuran (THF) was dried over sodium/benzophenone before distillation. 2-MeTHF was
dried over CaH2 and distilled onto activated molecular sieves (3 Å) prior to use. Diethylcarbonate
(DEC) and γ-Valerolactone (GVL) were stirred with K2CO3 and distilled onto activated molecular
sieves (3 Å) prior to use. 1,4-dibromo-2,5-bis[(2-hexyldecyl)oxy]-benzene (2), 4,7-di-2-thienyl-
2,1,3-benzothiadiazole (4), and 2-bromo-3-hexyl-thiophene (5) were prepared following literature
procedures. All NMR were recorded at 25 °C using CDCl3 on either a Varian Mercury 400 MHz,
Varian VNMRS-500 MHz, or a Varian VNMR-600 MHz. All spectra were referenced to CHCl3
(7.26 ppm), unless otherwise noted. PPDTBT prepared using Stille polycondensation (P4) was
previously synthesized following literature procedure.
28

Number average molecular weight (Mn) and polydispersity (Ð) were determined by size
exclusion chromatography (SEC) using a Viscotek GPC Max VE 2001 separation module and a
Viscotek Model 2501 UV detector, with 70 °C HPLC grade 1,2-dichlorobenzene (o-DCB) as
eluent at a flow rate of 0.6 mL/min on one 300 × 7.8 mm TSK-Gel GMHHR-H column (Tosoh
Corp). The instrument was calibrated vs. polystyrene standards (1050−3,800,000 g/mol), and data
42

were analysed using OmniSec 4.6.0 software. Polymer samples were dissolved in HPLC grade o-
dichlorobenzene at a concentration of 0.5 mg ml−1, stirred at 65 °C until dissolved, cooled to room
temperature, and filtered through a 0.2 μm PTFE filter.
For polymer thin-film measurements, solutions were spin-coated onto pre-cleaned glass
slides from o-dichlorobenzene (o-DCB) solutions at 7 mg/mL, which were then annealed at 150
°C for 30 minutes under N2. UV−vis absorption spectra were obtained on a Perkin-Elmer Lambda
950 spectrophotometer. Thicknesses of the samples and grazing incidence X-ray diffraction
(GIXRD) measurements were obtained using Rigaku diffractometer Ultima IV using a Cu Kα
radiation source (λ = 1.54 Å) in the reflectivity and grazing incidence X-ray diffraction mode,
respectively. Crystallite size was estimated using Scherrer’s equation:
τ = Kλ/(β cosθ) (1)
where τ is the mean size of the ordered domains, K is the dimensionless shape factor (K = 0.9), λ
is the x-ray wavelength, β is the line broadening at half the maximum intensity (FWHM) in radians,
and θ is the Bragg angle.
2.2.1 General procedure for PPDTBT synthesis using a high-pressure vessel
An oven-dried 15 mL high pressure vessel equipped with a stir-bar was stoppered with a rubber-
septum and cooled under a flow of N2. 2(0.25 mmol), 4 (0.25 mmol), carboxylic acid additive (1
equiv.), and Cs2CO3 (3 equiv.), and P(o-anisyl)3 (8 mol %) were added to the vessel. The solvent
was then added to the vessel via syringe to achieve the appropriate monomers’ concentration, and
it was degassed for 15 min. using N2. Pd2dba3 (2 mol %) was then added quickly and the rubber
septum replaced with a Teflon screw-cap with a rubber o-ring. The vessel was then submerged in
a pre-heated oil bath (120 °C). After the polymerization (16 hours), the reaction mixture was
43

cooled to room temperature, the product was dissolved in chlorobenzene, and then precipitated
into cold MeOH. The polymer product was filtered off and purified using Soxhlet extraction with
MeOH, hexanes, and CHCl3. The chloroform fraction was concentrated and precipitated into cold
methanol, the solid filtered off, and then dried overnight under vacuum.
2.2.2 General procedure for PPDTBT synthesis using a Schlenk-tube

An oven-dried 15 mL Schlenk-tube equipped with a stir-bar was stoppered with a rubber-septum
and cooled under a flow of N2. 2 (0.25 mmol), 4 (0.25 mmol), carboxylic acid additive (1 equiv.),
and Cs2CO3 (3 equiv.), and P(o-anisyl)3 (8 mol %) were added to the vessel. The vessel was then
vacuum-backfilled with N2 3 times. The solvent was then added to the vessel via syringe to achieve
the appropriate monomers’ concentration, and it was degassed for 15 min. using N2. Pd2dba3 (2
mol %) was then added quickly. The vessel was then submerged in a pre-heated oil bath (120 °C).
After the polymerization, the reaction mixture was cooled to room temperature, the product was
dissolved in chlorobenzene, and then precipitated into cold MeOH. The polymer product was
filtered off and purified using Soxhlet extraction with MeOH, hexanes, and CHCl3. The
chloroform fraction was concentrated and precipitated into cold methanol, the solid filtered off,
and then dried overnight under vacuum.
2.2.3 General procedure for P3HT synthesis using a Schlenk-tube
Similar to that of PPDTBT, but with 0.8 mmol of 5, 4 mol % Pd2dba3, 16 mol % P(o-anisyl)3, and
3 equiv. of Cs2CO3.
44

2.3 Results and Discussion
Depicted in Scheme 2.1, PPDTBT was synthesized under a variety of different conditions
from 2 and 4 with the outcomes reported in Table 2.1. For every entry in Table 2.1, the palladium
source (Pd2dba3), the phosphine ligand (P(o-anisyl)3), and the base (Cs2CO3) remained constant
throughout this study, however. Variations in the conditions include solvent, temperature, reaction
vessel, and carboxylate additive. The purpose of
Table 2.1 Conditions explored for PPDTBT synthesis. All polymerizations used Pd2dba3 as the
palladium source, P(o-anisyl)3 as the phosphine ligand, and Cs2CO3 as the base. Concentrations
were 0.4 M and performed in a high-pressure vessel unless otherwise noted.
Entry Solvent (M) Additive Yield (%)
[a]
Mn (ᴆ)
[a]
1
[b]
THF NDA 78 15 (2.1)
2 2-MeTHF NDA 81 17 (2.84)
3 GVL NDA - -
4
[c]
CPME NDA 94 31 (4.00)
5 DEC NDA - -
6 THF BiNDA 87 30 (3.47)
7 2-MeTHF BiNDA 78 12 (1.78)
8
[c]
CPME BiNDA 98 29 (4.80)
9 THF NPA 95 22 (3.63)
10 2-MeTHF NPA 78 12 (2.0)
11
[c]
CPME NPA 82 27 (4.10)
12
[c,d]
CPME NDA 78 41 (4.10)
a
Measured after polymer purification.
b
Reference 28.
c
Used Schlenk-Tube.
d
Modified conditions of
1 mol % Pd2dba3, 4 mol% P(o-anisyl)3, and 0.8 M concentration.
these variations was to find the optimal condition set, in terms of providing a large value for
molecular weight (Mn) and yield (%), with a renewable solvent.
We have previously reported on the high-pressure conditions using THF for the synthesis
of PPDTBT (Entry 1), which were originally described by Ozawa et al.
19
While these conditions
have proven successful for a variety of substrates, a pressurized reaction THF is a toxic, hazardous
45

solvent making its replacement imperative.
29–31
Shown with entries 2-4 of Table 2.1, we initially
investigated the effect changing the solvent, in reference to the original high-pressure THF
conditions that afforded PPDTBT in 78% and Mn of 15 kDa (entry 1) with NDA as the additive.
We found that 2-MeTHF (entry 2) provided satisfactory results with a slight improvement to THF
with a yield of 81 % and an Mn of 17 kDa. For CPME, which has a boiling point of 106 °C, it was
found that a high-pressure setting was unsuccessful since the temperature required is likely outside
of the range of catalyst stability and at 120 °C for 16 hours for no isolable polymer product was
obtained.
19,32,33
We found that an CPME can provide a higher Mn (30 kDa) and yield (94%) when
a Schlenk-tube is employed as the reaction flask and the reaction time extended to 72 hours (entry).
With both THF and 2-MeTHF, significant amounts of polymer precipitate from the reaction after
only 16 hours and so it is not believed that extending the reaction time for those solvents will
improve the Mn or yield significantly. Unfortunately, the carbonate based solvents GVL and DEC
did not provide any polymer product (entries 3 and 5). This is perhaps due to incompatibility with
the catalytic system or monomers employed. At the time of study, it was reported that GVL can
undergo ring-opening polymerizations with alkaline earth metal carboxylate salts.
34
This was
indeed observed with Cs2CO3 and K2CO3, but with Na2CO3 it was not. However, no
polymerization occurred to afford PPDTBT with Na2CO3 as the base and GVL as the solvent,
likely in part due to the low basicity of Na2CO3.
From these results we then decided to study the effect of changing the acid additive from
NDA to either BiNDA or NPA, which both contain carboxylates with bulky substituents like NDA.
Interestingly, BiNDA provided an improved yield (87%) and Mn (30 kDa) for THF (entry 6) in
comparison to entry 1, while that for CPME (entry 8) shows a similar yield (98%) and M n (29
kDa) to that of when NDA is employed (entry 4). 2-MeTHF (entry 7) shows a diminished yield
46

(78%) and Mn (12 kDa) compared to when NDA is used (entry 2). Relative to entry 1, NPA
provided an improved yield (95%) and Mn (22 kDa) for THF (entry 9). For 2-MeTHF (entry 10),
NPA provided similar results to that of BiNDA (entry 7) with an Mn of 12 kDa and a yield of 78%.
For CPME (entry 11), both the yield (82%) and Mn (27 kDa) diminished relative to that of when
BiNDA (entry 8) or NDA (entry 4) are used. It is interesting to note the relationship between the
solvent and carboxylate additive to the outcome of the polymerization, specifically in regards to
Mn and yield. This is most notable with THF when comparing entries 1, 6, and 9. However, at this
time, it is unclear the exact effect of the acid additive on the yield and M n, since the acid additive
plays an intricate role in the mechanistic pathway for DArP, such as in the concerted metalation
deprotonation (CMD) step.
35

Since CPME consistently provided us the best Mn and a good yield, we want to further
improve upon the conditions of this solvent. We found that by increasing the concentration from
0.4 M to 0.8 M we were able to achieve a much higher Mn of 41 kDa, although the yield decreased
to 78%. We felt these were the most optimal conditions for PPDTBT synthesis, and were then
interested to confirm the polymer structure and apply it towards the synthesis of P3HT.
In regards to structural analysis, 1H NMR spectroscopy, absorbance spectroscopy, and
GIXRD were used to compare the synthesized PPDTBT polymers with those previously reported
using DArP and Stille. The analysis was performed for the most satisfactory polymer products,
which provided the highest Mn for the different solvents studied. Specifically, entries 12, 2, and 6
from Table 2.1 were analysed and are labelled as P1, P2, and P3, respectively. The
1
H-NMR
spectra (see Appendix A) for these materials matched that of the previously reported PPDTBT
prepared using DArP, with no observable deviation.
47

The absorbance spectra for polymers P1-P3 are shown in Figure 2.2a with a Stille-
PPDTBT (P4) for reference. The absorption profiles for DArP polymers P1-P3 all match that of
P4 (656 nm), with a λmax ranging from 654-658 nm for the polymers P1-P3. A vibronic shoulder
is apparent for all of the polymers, indicating a minimization, if not exclusion, of β-defects. The
absorption coefficients (α) for polymers P1-P3 all appear to follow a trend based on the Mn value.
P1, with the highest value for Mn at 41 kDa, possesses the largest value for α (107 × 10
4
cm
-1
,
Figure 2.2 (a) Absorption profiles of PPDTBT polymers P1-P4. (b) GIXRD patterns for
PPDTBT polymers P1-P4.

48

Table 2.2), while P2, with the lowest value for Mn (between polymers P1-P3) at 17 kDa has the
smallest value for α (63 × 10
4
cm
-1
). Interestingly, DArP polymers P1 and P3 have larger values
for α than the Stille-PPDTBT, P4. This may be due to trace metallic residues or structural
irregularities from Stille polymerization in P4 causing poor interactions between polymer chains
that help facilitate light absorbance.
Shown in Figure 2.2b, the diffraction patterns from GIXRD shows a similar d100 spacing
for polymers P1-P4. This similarity in the lamellar spacing for the materials is expected since the
alkyl chains on the dialkoxyphenylene donor are the same for all of the PPDTBT polymers studied.
Crystallite size for polymers P1-P4 were calculated using the Scherrer equation (see Appendix A
for 2θ and FWHM values). The crystallite size for polymers P1, P2, and P4 are all relatively similar
(14.7-15.5 nm), while that for P3 is slightly larger (17.5 nm). This and the apparent larger degree
of crystallinity for P3 may suggest improved
Table 2.2 (a) Absorbance spectra for PPDTBT polymers P1-P4. (b) GIXRD patterns for PPDTBT
polymers P1-P4
Entry Conditions Used
(Table 2.1)
λmax (nm)
a
;α (cm
-1
)
a
d100 (Å)
a
Crystallite
Size (nm)
a
P1 Entry 12 658; 107 × 10
4
18.8 14.7
P2 Entry 2 658; 63 × 10
4
19.0 15.3
P3 Entry 6 654; 85 × 10
4
18.8 17.5
P4
b
Stille 656; 72 × 10
4
19.0 15.5
a
Measured on polymer films prepared from a 7 mg/mL DCB solution and annealed at 150 °C for
30 minutes.
b
Mn = 65.0 kDa, ᴆ = 1.96.
purity of the polymer sample allowing for increased crystalline domain sizes and abundance, given
that the polymer products were all subjected to identical conditions for purification and film
preparation. Although, the cause of this is still unclear.
49

Because CPME provided the best results both in yield and Mn for PPDTBT, we were
interested to see its effect toward the synthesis of P3HT. Also, while PPDTBT is a well
characterized polymer, especially using different DArP protocols, the complexities associated its
structure and potential defects arising from such do not allow for as thorough of analysis as P3HT,
for example. The defect-analysis regarding P3HT has been well-studied, and offers another handle
for evaluating the efficacy of a new DArP synthetic method to provide the minimization or absence
of defects. However, because of the physical property differences, e.g. solubility, between P3HT
and PPDTBT, the direct translation for the conditions for used for PPDTBT synthesis was not
successful, shown in Table 2.2. Specifically, the high-concentration (0.8 M) and low catalyst-
loading (1 mol %) found successful for PPDTBT did not afford any polymer product for P3HT
(entry 1). Also, it was found that lowering the concentration (0.2 M) and raising the catalyst
loading (4 mol %) only afforded insoluble polymeric material that could not be characterized.
Either the Mn was too high to allow for solubility or the polymer had high levels of embedded
defects, such as β-defects (entry 2). However, when the reaction time was decreased from 72 hours
to 24 hours we were able to obtain isolable polymer product with a yield of 34% and 12 kDa, and
no insoluble material was observed (entry 3). It is possible that more extensive optimizations can
be carried out for the synthesis of P3HT to improve the yield and Mn, but we only wished to see if
CPME can be successfully employed for the synthesis of P3HT with a minimization of defects.
The value for λmax (555 nm) and α (103 × 10
4
cm
-1
) show agreement with P3HT synthesized using
DArP, depicted in Figure 2.3a and 2.3b, respectively as well as the values for d100 (16.8 Å).
30

Shown in Figure 2.3c, the regio-regularity of the synthesized P3HT (P5) was determined using
1
H-NMR spectroscopy (CDCl3, 25 °C). The rr was determined using previously described
methods, calculated by determining the ratio of the integrals spanning from δ (ppm) 2.90-2.65 and
50

2.90-2.40. Based on this ratio, the rr was found to be 93%, and the presence of β-defects (δ2.35)
were not observed.
31,36
Also, the presence of a vibronic shoulder (Figure 2.3a) and the value for
d100 (16.8 Å) indirectly show the absence or undetectable level of β-defects.
31
This value for rr is
similar to that obtained with other ethereal solvents, such as THF and 2-MeTHF, at 120 °C, which
were 93.8% and 96.2% rr, repsectively.
31
We believe the rr can likely be improved through
lowering the catalyst loading, but with the given set of conditions we found that lowering the
catalyst loading provided no isolable polymer product. These results, however, provide support
for CPME to produce polymer products with a very low to undetectable level of defects. Furthering
the scope of CPME towards the synthesis of other conjugated polymers using DArP will likely
take some optimization, in regards to temperature and time, but this solvent successfully presents
itself as a greener, more benign alternative to solvents commonly employed.
2.4 Conclusions
In summary, we report the application of green solvents towards the synthesis of PPDTBT
and P3HT via DArP. Solvents studied include 2-MeTHF, CPME, GVL, and DEC. The additives
BiNDA and NPA were also evaluated for their ability to produce quality polymer products, e.g.
high Mn and yield. Of the solvents studied we found that CPME provided the best results towards
the synthesis of PPDTBT, affording polymer product with Mn of 41 kDa and a yield of 78%,
Figure 2.3 (a) Absorption spectrum of P3HT (P5) synthesized in Table 2.2. (b) GIXRD diffraction
pattern for P3HT (P5). (c) Determination of the region-regularity (RR) of P3HT synthesized using
DArP via 1H NMR spectroscopy. Collected in CDCl3 at 25 °C and 600 MHz.
51

significantly higher than the value of 15 kDa when the more hazardous THF is employed as the
solvent under high-pressure conditions. In regards to the additives studied, NPA and BiNDA, a
solvent dependence was observed and the effect of this is still under investigation. However,
BiNDA provided a major improvement in comparison to NDA for the synthesis of PPDTBT when
THF is the solvent, increasing the Mn and yield from 15 kDa and 70% to 30 kDa and 87%.
Application of CPME towards P3HT synthesis provided a polymer product with 93% rr, no
detected β-defects, at 12 kDa. We believe the results here provide an initial step towards the
inclusion of green solvents in DArP, further its environmental compatibility, low-cost, and
reduction of chemical hazards relative to other conjugated polymer synthetic methods. Future work
will seek to expand upon the scope presented here with the inclusion of other reagents and
monomers that align with the principles of green chemistry.

52

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58

Chapter 3: Influence of an Ester Directing-Group on Defect Formation in the Synthesis of
Conjugated Polymers via Direct Arylation Polymerization (DArP) using Sustainable
Solvents

3.1 Introduction
Interest in conjugated polymers is ever increasing, due to the wide-range of potential
applications these materials can be used for.
1,2
Primarily, their inclusion in organic electronic
applications, such as light-emitting diodes, thin-film transistors, and photovoltaics is of
considerable interest since they offer a low-cost alternative to their inorganic counterparts.
3–5
In
particular, bulk-heterojunction polymer solar cells have experienced a renaissance of sorts due to
the optimization of non-fullerene acceptors (NFA).
6–8
Power conversion efficiencies (PCE) in
excess of 15% have been achieved in these devices, providing strong motivation to further advance
this technology as a viable alternative energy source.
9,10
A polymer of interest in such solar cells
is poly[5,5′‐bis(2‐butyloctyl)‐(2,2′‐bithiophene)‐4,4′‐dicarboxylate‐alt‐5,5′‐2,2′‐bithiophene]
(PDCBT), which is shown in Scheme 3.1. This polymer has great potential, given its relative ease
of synthesis (Scheme 3.2 and 3.3) and the performance in both fullerene (PCE of >7%) and non-
fullerene (PCE of >10%) solar cells is very desirable.
11–15
The short synthetic procedure for
PDCBT, based on only a few steps from commercial starting materials, is consistent with
scalability, a key guiding principle of sustainability in conjugated polymers.
16,17
Another guiding
principle is the avoidance of highly hazardous reagents, e.g. pyrophoric or acute toxicants,
However, the synthesis of PDCBT, and almost all conjugated polymers used in solar cells are still
reliant on Migita-Stille (Stille) polymerizations, which invoke the use of an alkylstannane moiety
59

for transmetallation, or Suzuki-Miyaura (Suzuki) polymerizations, which require the inclusion of
an organoboronate on the monomer. This undermines the sustainability of conjugated polymers,
through the use of highly hazardous reagents, cryogenic conditions, and a large accumulation of
toxic byproducts.
In contrast, direct arylation polymerization (DArP) provides an avenue for conjugated
polymer synthesis that is streamlined and sustainable, via the direct functionalization of C-H bonds
during the polymerization.
18–24
Research efforts towards further improving the sustainability of
DArP protocols has increased, with studies that investigate changing the solvent or transition metal
catalyst to more sustainable alternatives.
25–28
This change to sustainable sources, be it the solvent
or transition metal catalyst, present major challenges as the chemistry associated with the desired
chemical transformation can be highly dependent on the solvent or catalyst employed.
29,30
To
further develop and improve upon such changes, a paradigm shift has occurred within organic
chemistry to develop more sustainable reaction conditions.
31–33
Extension of this field to
conjugated polymer synthesis, or polymer synthesis in general, is not a straightforward pursuit, as
mentioned above.
30,34
This is why the focus on this area has expanded, since there are many
challenges still to be faced with regards to finding broadly applicable, truly sustainable conditions
for conjugated polymer synthesis. Recently, we have reported DArP conditions using cyclopentyl
methyl ether (CPME), which is a sustainable solvent allowing for the synthesis of conjugated
polymers with a minimized environmental impact.26 CPME is advantageous for large scale
applications because it can be prepared in a waste-free process with starting materials sourced from
biomass, it is not classified as a reproductive toxin or carcinogen, and it is not a peroxide former
like 2-methyltetrahydrofuran (2-MeTHF).
35,36

60

From our previous study, the reaction conditions using CPME required extended times (72
hours) compared to comparable DArP protocols (16 hours). In regards to donor-acceptor
copolymer synthesis, only a single copolymer, poly[(2,5-bis(2-hexyldecyloxy)phenylene)-alt-
(4,7-di(thiophen-2-yl)benzo[c][1,2,5]thiadiazole) (PPDTBT), which is shown in Scheme 3.1
(top), was reported. Furthermore, the sustainable solvent anisole, which can be derived from
biomass, does not form peroxides, and has been utilized for the fabrication of polymer solar cells
with good efficiencies (PCE > 11%), was not studied.
37–40
With this in mind, we were emboldened
to explore improved reaction conditions with sustainable solvents and apply them to a broader
scope of monomers that have not been studied with DArP.
Herein, we report the synthesis of PDCBT using the sustainable solvents CPME and
anisole, with a goal of elucidating the influence of monomer structure, specifically an ester
directing group, on the capacity for defect formation, which is described below. We find that the
most effective conditions with CPME allow for the rapid synthesis of PDCBT in less than 1 hour
Scheme 3.1 Investigation of DArP using sustainable solvents towards the synthesis of PPDTBT
(top), and the application of such solvents towards the synthesis of PDCBT, PDCBTT, and
PDCBTz (bottom).
61

(Mn =13.6 kDa and yield of 59%, shown in Table 3.1), which is a significantly lower reaction time
than the previously reported for PPDTBT (reaction time of 72 hours).
26
It was observed, however,
that gelation of the polymerization can occur leading to insoluble material if the timing of the
reaction is further extended. This is believed to be potentially due to the formation of crosslinking
or branching (β) defects, which has been observed for bithiophene based copolymers prepared via
DArP.
41
Through analysis using GIXRD, UV-vis absorption spectroscopy, and 1H-NMR
spectroscopy we show that branching (β) defects are the likely cause of this gelation. We propose
that activation of β-protons on the bithiophene comonomer and subsequent defect formation is
likely enhanced by the coordinative and directing ability of the ester moiety on the acceptor unit
of PDCBT.
42–44
While many studies have been conducted to determine the formation of defects
with DArP, the effect of a directing-group, such as an ester, has not been accounted for or
previously realized.
45

In order to explore the impact of the ester directing groups on the adjacent β-protons, we
applied the polymerization conditions used for PDCBT towards the synthesis of poly[5,5′‐bis(2‐
butyloctyl)‐(2,2′‐bithiophene)‐4,4′‐dicarboxylate‐alt‐2,5‐[3,2-b]thienothiophene] (PDCTT) and
poly[5,5′‐bis(2‐butyloctyl)‐(2,2′‐bithiophene)‐4,4′‐dicarboxylate‐alt‐5,5′‐2,2′‐bithiazole]
(PDCBTz), which are shown in Scheme 3.1. The thieno[3,2-b]thiophene (TT) and 2,2’bithiazole
(BTz) provide simple model compounds to study how a more electron rich monomer or electron
deficient monomer may inhibit or accelerate the formation of branching defects, respectively. We
find that branching occurs excessively with PDCBTz, preventing the isolation of high Mn polymer,
but not PDCTT. This investigation and the findings herein provide valuable insight regarding
functional group tolerance for DArP.

62

3.2 Experimental
3.2.1 General Methods
All reagents were purchased from VWR and used as received, unless otherwise noted.
Pd(PPh3)2Cl2 was purchased from Beantown Chemical and used as received. Pd2dba3 was
purchased from Matrix Scientific and used as received. P(o-anisyl)3 was purchased from TCI and
used as received. Cs2CO3 and K2CO3 were ground to a fine powder and dried in a vacuum oven
(120 °C) overnight then stored in a desiccator before use. Anhydrous cyclopentyl methyl ether
(CPME) was purchased from Acros Organics and used as received. Compounds 2-12 were
prepared following literature procedures. See Appendix B for complete synthetic details in regards
to monomer synthesis. 5,5’-bis(trimethylstannyl)-2,2’-bithiophene (13) used for Stille
polymerization was previously prepared following literature procedure.
46

All NMR were recorded at 25 °C using CDCl3 on either a Varian Mercury 400 MHz,
Varian VNMRS-500 MHz, or a Varian VNMR-600 MHz. All spectra were referenced to CHCl3
(7.26 ppm), unless otherwise noted. Number average molecular weight (Mn) and polydispersity
(Ð) were determined by size exclusion chromatography (SEC) using a Viscotek GPC Max VE
2001 separation module and a Viscotek Model 2501 UV detector, with 60 °C HPLC grade 1,2-
dichlorobenzene (o-DCB) as eluent at a flow rate of 0.6 mL/min on one 300 × 7.8 mm TSK-Gel
GMHHR-H column (Tosoh Corp). The instrument was Calibrated vs. polystyrene standards
(1050−3,800,000 g/mol), and data were analysed using OmniSec 4.6.0 software. Polymer samples
were dissolved in HPLC grade o-dichlorobenzene at a concentration of 0.5 mg ml
−1
, stirred at 65
°C until dissolved, cooled to room temperature, and filtered through a 0.2 μm PTFE filter.
63

For polymer thin-film measurements, solutions were spin-coated onto pre-cleaned glass
slides from chloroform solutions at 7 mg/mL, which were then annealed at 150 °C for 30 minutes
under N2. UV−vis absorption spectra were obtained on a Perkin-Elmer Lambda 950
spectrophotometer. Thicknesses of the samples and grazing incidence X-ray diffraction (GIXRD)
measurements were obtained using Rigaku diffractometer Ultima IV using a Cu Kα radiation
source (λ = 1.54 Å) in the reflectivity and grazing incidence X-ray diffraction mode, respectively.
Crystallite size was estimated using Scherrer’s equation, shown with equation 1:
τ = Kλ/(β cosθ) (1)
where τ is the mean size of the ordered domains, K is the dimensionless shape factor (K = 0.9), λ
is the x-ray wavelength, β is the line broadening at half the maximum intensity (FWHM) in radians,
and θ is the Bragg angle.
3.2.2 Synthesis of PDCBT via Stille
To a 3-neck round bottom flask equipped with a stir-bar, nitrogen inlet, glass-stopper,
Teflon septum, condenser, and under an inert, nitrogen atmosphere was added 5,5’-
bis(trimethylstannyl)-2,2’-bithiophene (104 mg, 0.14 mmol, 1 equiv.) and 5 (68.5 mg, 0.14 mmol,
1 equiv.). Toluene (4.5 mL) was then added and the mixture degassed with N2 for 20 minutes.
Pd(PPh3)4 (11 mg, 0.007 mmol, 5 mol%) was added quickly to the flask, and it was then degassed
again for 20 minutes. The Teflon septum was replaced with a glass stopper, and the mixture was
then heated at 110 °C for 72 hours. CHCl3 (5 mL) was added with gentle heating to dissolve the
solids, and the mixture was precipitated into a chilled 10% NH4OH/MeOH solution with high-
stirring. The solids were then filtered into a Soxhlet thimble and purified via Soxhlet extraction
(MeOH, hexanes, and CHCl3). The CHCl3 fraction was concentrated, transferred to a tared vial,
64

the solvent stripped, and the polymer further dried overnight under vacuum (~100 mtorr).
1
H-NMR
(500 MHz, CDCl3):
1
H-NMR (500 MHz, CDCl3): δ(ppm) 7.56-7.46 (br, 4H), 7.20 (br, 2H), 4.21
(d, J = 5.0 Hz, 4H), 1.75 (br, 2H), 1.32-1.28 (br, 32H), 0.91-0.86 (br, 12H). Consistent with
literature reports.
47

3.2.3 Synthesis of PDCBT via DArP (Entry 3 of Table 3.1)
An oven dried, high-pressure vessel (15 mL) was capped with an inverted red-rubber
septum and cooled under a stream of nitrogen for 15 minutes. Compound 4 (100 mg, 0.17 mmol,
1 equiv.), neodecanoic acid (29 mg, 0.17 mmol, 1 equiv), 5,5’-dibromo-2,2’-bithiophene (55 mg,
0.17 mmol, 1 equiv.), P(o-anisyl)3 (9.5 mg, 0.16 equiv), PdCl2(PPh3)2 ( 4.77 mg, 0.0068 mmol,
0.04 equiv), and Cs2CO3 (180 mg, mmol, 3.2 equiv) was added. The vessel was then sparged with
a stream of nitrogen for 10 minutes. CPME (1.7 mL), which was from a 5 mL stock that had been
degassed prior with N2 for 15 minutes, was quickly added and the rubber septum quickly replaced
with a Teflon screwcap equipped with a rubber o-ring. The sealed vial was the placed into a
preheated oil bath (110 °C) and stirred for 43 minutes. The vial was then removed from heat,
CHCl3 (5 mL) was added with gentle heating to dissolve the solids, and the mixture was
precipitated into a chilled 10% NH4OH/MeOH solution with high-stirring. The solids were then
filtered into a Soxhlet thimble and purified via Soxhlet extraction (MeOH, hexanes, and CHCl3).
The CHCl3 fraction was concentrated, transferred to a tared vial, the solvent stripped, and the
polymer further dried overnight under vacuum (~100 mtorr).
1
H-NMR (500 MHz, CDCl3): δ(ppm)
7.54-7.46 (br, 4H), 7.20 (br, 2H), 4.21 (d, J = 5.0 Hz, 4H), 1.75 (br, 2H), 1.32-1.28 (br, 32H), 0.91-
0.86 (br, 12H). Consistent with literature reports.
47

65

3.2.4 Synthesis of PDCTT via DArP (Entry 6 of Table 3.1)
Similar to that of PDCBT but with thieno[3,2-b]thiophene ( 50.7 mg, 0.17 mmol, 1 equiv.) in place
of 5,5’-dibromo-2,2’-bithiophene.
1
H-NMR (500 MHz, CDCl3): δ(ppm) 7.76-7.57 (br, 4H), 4.19
(br, 4H), 1.76 (br, 2H), 1.29-0.79 (br, 44H). Consistent with literature reports.
47

3.2.5 Synthesis of PDCBTz via DArP (Entry 7 of Table 3.1)
Similar to that of PDCBT but with 5,5’-dibromo-2,2’-bithizaole ( 55.4 mg, 0.17 mmol, 1 equiv.)
in place of 5,5’-dibromo-2,2’-bithiophene.
1
H-NMR (600 MHz, CDCl3): δ(ppm) 8.20-8.18 (br,
2H), 7.62-7.59 (br, 2H), 4.21 (br, 4H), 1.75 (br, 2H), 1.31-1.27 (br, 32H), 0.90-0.86 (br, 12H).

3.3 Results and Discussion
3.3.1 Polymer Synthesis of PDCBT via DArP
As depicted in Scheme 3.3 (see Appendix B for complete details), the monomer syntheses
follow similar routes to those found in the literature with the exception of compound 4. It was
found that the nickel-catalysed reductive homocoupling was low yielding (20-30%) in our hands,
impeding the necessary scale-up to allow for the optimization of the polymerization step. Recently,
Suzuki-Miyura conditions have been used for the preparation of similar compounds, albeit with
simpler alkyl chains on the ester moiety, such as methyl or ethyl, and so these were successfully
adapted to allow for a highly scalable synthesis of compound 4. As reported by others, the
Scheme 3.2 Synthesis of PDCBT via Stille (top) and PDCBT, PDCTT, and PDCBTz vi DArP
(bottom).
66

Table 3.1 Detailed conditions and polymerization outcomes for the synthesis of PDCBT, PDCTT,
and PDCBTz.
Entry Polymer Pd source
a
Solvent
(M)
Base
(equiv.)
Temp.
(°C)
Time
(hours)
Yield
(%)
b
Mn
(kDa)
b

Ð
b
1 PDCBT Pd2dba3 THF
(0.2)
Cs2CO3
(3)
120 16 NP NP NP
2

PDCBT Pd2dba3 CPME
(0.2)
Cs2CO3
(3.2)
110 16 72 7.9 2.08
3 PDCBT PdCl2(PPh3)2 CPME
(0.2)
Cs2CO3
(3.2)
110 2 insoluble insoluble insoluble
4 PDCBT PdCl2(PPh3)2 CPME
(0.2)
Cs2CO3
(3.2)
110 0.72 59 13.8 3.30
5
c
PDCBT PdCl2(PPh3)2 CPME
(0.2)
Cs2CO3
(2)
110 16 NP NP NP
6

PDCBT PdCl2(PPh3)2 CPME
(0.2)
K2CO3
(3.2)
110 16 NP NP NP
7

PDCBT PdCl2(PPh3)2 Anisole
(0.2)
Cs2CO3
(3.2)
110 16 77 8.3 2.13
8 PDCTT PdCl2(PPh3)2 CPME
(0.2)
Cs2CO3
(3.2)
110 16 90 26.4 2.33
9 PDCBTz PdCl2(PPh3)2 CPME
(0.2)
Cs2CO3
(3.2)
110 1.1 46 4.9 4.09
10 PDCBTz PdCl2(PPh3)2 CPME
(0.2)
Cs2CO3
(3.2)
110 1 54 3.4 2.62
Stille

PDCBT Pd(PPh3)4 Toluene
(0.06)
- 110 72 95 24.0 3.08
a
2 mol% loading for when Pd2dba3 is employed and 4 mol% for when PdCl2(PPh3)2 is employed.
b

Determined after purification of the polymers via Soxhlet extraction.
c
Catalyst loading lowered
from 4 mol% to 2 mol%. NP indicates an unsatisfactory or no precipitation from the reaction
mixture prohibiting further purification.
bromination of compound 4, which is required for Stille polymerization, proceeds with low levels
of regio-selectivity leading to an inseparable byproduct if not performed carefully.
47
Due to these
complications with the synthesis of monomer 5, it was deemed that the donor should be
halogenated for DArP studies considering that halogenation of the donor-units can proceed much
more simply without harsh conditions, such as trifluoroacetic acid for a solvent. Furthermore, the
high-pressure DArP conditions originally developed by Ozawa et al. and Leclerc et al., which we
have demonstrated to be compatible with sustainable solvents, employ a halogenated donor-unit
leaving the site for C-H activation on the acceptor-unit.
22,41
Thus, the functionalization pattern
shown in Scheme 3.2, with the donor-unit being halogenated, was deemed the best route for
67

polymer synthesis in general. Compounds 7, 9, and 12 were all prepared following their respective
literature procedures.
As depicted in Scheme 3.2, with the results in Table 3.1 (Entry Stille), PDCBT was
prepared via Stille polymerization following literature procedure with a M n of 24 kDa in 95%
yield.
11
An initial attempt for polymerization via DArP was performed using THF as a solvent, in
order to see how polymerization proceeds using a more general and often applied set of conditions
(Entry 1 of Table 3.1).
48,49
Interestingly, no polymer precipitate was formed after the reaction.
This led us to conclude that the solvent, Pd-source, and temperature could be having an unforeseen,
adverse effect on the synthesis of the polymer via DArP. Specifically, in regards to solvent,
PDCBT prepared via Stille polymerization proceeds exclusively in toluene, directing us to believe
that a more non-polar solvent may be beneficial. With this in mind, we chose CPME as the next
solvent for study, given its development as a sustainable solvent for conjugated polymer synthesis
and that it is less-polar than THF. As shown in Entry 2 of Table 3.1, changing the solvent from
THF to CPME afforded polymer product in 72% yield with an Mn of 7.9 kDa. As a next step, we
chose to optimize the identity of the Pd-source, and we selected PdCl2(PPh3)2 since it has been
shown to provide an effective catalyst for DArP and other cross-coupling methodologies.
41,50–52

With the changes in solvent and Pd-source, we found that the polymerization mixture completely
gelled in 2 hours, to yield a polymer product that was prohibitively insoluble (Entry 3 of Table
3.1). Specifically, the material isolated from the polymerization could not be isolated from the
CHCl3 or chlorobenzene (CB) Soxhlet fractions. This insolubility could be from achievement of a
very high-Mn polymer product or from the introduction of defects due to undesired couplings, such
as donor-donor homocouplings or branching (β) defects.
24,41,53
The cause of this observed catalyst
dependence, can likely be traced to the higher reactivity for PdCl2(PPh3)2 in certain cross-coupling
68

reactions and within DArP for certain monomers. Specifically, Leclerc et al. have reported
conditions for the polymerization of substituted bithiophene based monomers using PdCl 2(PPh3)2
with P(o-anisyl)3, achieving Mn of 52 kDa and a yield of 90%.
41
The results presented here as well
as those described by Leclerc et al, indicate a preference for PdCl2(PPh3)2 over Pd2dba3 when using
bithiophene based monomers (Entries 2 and 4 of Table 3.1, respectively). Based on previous
studies, PdCl2(PPh3)2 has been shown to form anionic species (Pd
0
(L)2(X)
-1
) from the highly
reactive intermediate Pd
0
(L)2, both of which exhibit faster rates of oxidative addition than the
Pd
0
(L)4 likely formed from Pd2dba3.
52,54
Formation of such a species, however, requires the in situ
reduction of the Pd
II
-precatalyst (PdCl2(PPh3)2), which may only be a favorable process for only
certain monomers, such as functionalized bithiophenes.
55
Furthermore, the dba ligand (from
Pd2dba3) has been reported to stabilize the Pd
0
species to the point that it impedes catalysis or that
it can interfere with the desired catalytic transformation, which may be occurring with the
polymerizations described here.
55,56
While such reactivity is dependent on the monomers under
study, such a heightened reactivity for PdCl2(PPh)3 is interesting given the prevalence of Pd2dba3
in donor-acceptor copolymer synthesis via DArP. To see if a soluble polymer product could be
Scheme 3.3 Monomer synthesis.
69

obtained that would allow for structural characterization, the reaction time was shortened and the
polymerization was closely monitored so that it can be stopped just at the onset of gelation, where
the polymerization changes from a red to violet-red color. It was found that after 43 minutes, or
0.72 hours, the onset of gelation occurs and a polymer product that exhibits good solubility
(allowing for complete purification and isolation via Soxhlet extraction) is obtained (Entry 4 of
Table 3.1) with a satisfactory Mn (13.8 kDa) and yield (59%). These conditions provide significant
improvement from the original high-pressure THF based conditions originally used (no polymer
product after 16 hours), and also the polymerizations reported in our previous study, where 72
hours was required to provide optimal results with CPME.
26
Additional efforts were made to
control the observed high reactivity, by lowering the equivalents of Cs2CO3 from 3.2 to 2.0 and
the catalyst loading from 4 mol% to 2 mol% (Entry 5 of Table 3.1) and changing the base to
K2CO3 (Entry 6 of Table 3.1). However, these changes did not provide a satisfactory polymer
precipitate from their respective reaction mixtures. With regards to changing the equivalents of
base (Entry 5), the result of no polymer product forming is likely due to only 1 equivalent of
reactive base (Cs2CO3) being presented with the remainder being quenched to CsHCO3, as
previously discussed by Ozawa et al.
22,57
Although the catalyst loading has been lowered, going
from 4 to 2 mol% will likely not have as detrimental of effect as lowering the base. This is because
many DArP protocols, using similar conditions, use a catalyst loading of 1 to 2 mol%. In our
previous study regarding sustainable solvents, we found that lowering the catalyst loading from 4
to 1 mol% actually led to an increase in Mn (from 31 to 41 kDa) for PPDTBT.
26
Furthermore,
Leclerc’s study regarding the DArP of dialkyl bithiophenes shows that the inherent reactivity of
the monomer protons, such as the α or β protons, is what determines the propensity for defect
formation for a given condition set, which is further discussed below.
41
Therefore, monomers with
70

a greater potential for defect formation, such as those with an ester directing group, should be
tailored or functionalized so as to prohibit the undesired activation of branching sites, since the
tuning of reaction conditions, such as equivalents or identity of base and loading of catalyst, cannot
necessarily allow for the exclusion of defects.
We were then interested to see the effect of changing the solvent, specifically with anisole.
Anisole is less polar than THF with a dielectric constant of 4.33 versus 7.58 and, as described
earlier, can be used as a more sustainable solvent for conjugated polymer synthesis and
processing.
39,58,59
The dielectric constant is closer to that of CPME as well, which is at 4.76.
36

Interestingly, anisole was found to slow the rate of polymerization, by observation, since no
gelation was observed (Entry 7 of Table 3.1). Consequentially, this led to a polymer with lower
Mn (8.3 kDa), but an improved yield (77%). The dependence of the reaction on the choice of
solvent is difficult to determine given the critical role of the solvent within this type of
transformation, e.g. solubility of the base, coordination to palladium, and potential activation of
halogens.
52,60,61
Given this, it is possible that the slight increase in polarity for CPME over anisole
(4.76 versus 4.33, respectively) may help to stabilize transition states, intermediates, or provide
improved solubility of the growing polymer chain. It is likely that through more extensive
optimization or with a different copolymer the reaction time and outcome of the polymerization
using anisole can be improved, and so anisole should not be discounted as a sustainable solvent
for DArP.
3.3.2
1
H-NMR Characterization of DArP-PDCBT
To determine if the structure of the DArP-synthesized polymers match that of the known
Stille synthesized PDCBT,
1
H-NMR spectroscopy was used, which is shown in Figure 3.1. The
polymers, both those prepared using DArP and Stille, exhibited excellent solubility in chloroform
71

allowing for well-defined resonances to be obtained in the spectra. As shown in Figure 3.1 (bottom
spectrum), the Stille polymer shows three well defined resonances centered at 7.54, 7.46, and 7.20
ppm (A-C). These are in agreement with the observed literature values.
11,47
End-group assignments
are based on the observed resonances for monomers and model compounds collected in CDCl 3
with identical or similar structure.
11,47,62
Interestingly, end-groups associated with destannylated
bithiophene are observed at 7.25 ppm (label h, Figure 3.1). This is likely due to destannylation,
which has been observed for electron-rich heterocyclic stannanes.
63

Figure 3.1 1H-NMR (CDCl3, 25 °C) of PDCBT prepared via DArP using the conditions outlined
in Table 3.1: entry 4 (top), entry 7 (middle), and the Stille reference (bottom). End-group
assignments are denoted by the lowercase letters (a-n) and the major resonances by the uppercase
(A-C). For polymers prepared via DArP, acceptor-acceptor and donor-donor homocouplings are
denoted by the characters, α and δ, respectively. Resonance labels with an asterisk (*) are not
distinctly observed due to potential overlap (f* at 7.26 and c* at 7.55 ppm). All spectra referenced
to CHCl3 at 7.26 ppm.
72

For the polymers prepared via DArP (Figure 3.1, top and middle), the major resonances
(A, B, and C) align very well with the Stille-reference polymer. Also, the smaller, distinct
resonances (a-h, Figure 3.1) can be assigned to the expected end-groups of either the ester
functionalized bithiophene or bithiophene, indicating good structural fidelity for the DArP
polymers. Importantly, acceptor-acceptor homocoupling peaks (α), which can occur via an
oxidative coupling and has been reported for monomers of similar structure, e.g. ester-
functionalized thiophenes, are not observed at 7.66 ppm (Figure 3.1, top and middle).
50,64
An
expanded view of this region (7.75-7.60 ppm) in Appendix B (Figure B13), shows that acceptor-
acceptor homocouplings are not present and that the small resonances near this point are also in
the Stille-PDCBT. These smaller resonances present in both DArP-PDCBT and Stille-PDCBT
likely correspond to the penultimate protons near the terminus of the polymer. Also, donor-donor
homocouplings (δ) are not observed at 6.98 ppm.
65
End-groups corresponding to the bithiophene
end-group are easily apparent (d-h, Figure 3.1). As with the Stille-reference, resonances
corresponding to f* are not observed, likely due to overlap with the major resonance from solvent
(CHCl3) at 7.26 ppm. Shoulders near 7.45 ppm corresponding to proton d, are better defined in the
DArP PDCBT polymers, compared with the Stille-reference. These results indicate that the
conditions employed for entry 4 and 7 of Table 3.1 provide polymer product with good structural
fidelity with regards to an absence of α and δ homocouplings, as observed by
1
H-NMR. Of the two
homocoupling defects, δ homocouplings would be the likely cause of insoluble material to form,
since no solubilizing alkyl chains are present on the bithiophene donor. Given their absence, in the
case of Entry 4, this indicates that gelation and formation of insoluble material is likely occurring
through crosslinking or β-defect formation, although these structural features are challenging to
observe via
1
H-NMR.
24,41,66,67

73

This conclusion on potential β-defect formation for PDCBT is reached based on previous
DArP studies we have performed, which describe the defect free synthesis of P3HT and PPDTBT
using similar conditions (Figure 3.2a).
26,68
Similar conditions were also applied towards the
synthesis of PPDBTTPD (Figure 3.2a), which possesses numerous, unobstructed β-protons.
49
In
each of these studies, no prohibitively insoluble material was obtained (even when precipitation
during the polymerization was observed), and thorough characterization of these polymers
confirmed an absence of β-defects. In the case of the aforementioned polymers (P3HT, PPDTBT,
Figure 3.2 (a) Polymers (P3HT and PPDTBT) for which the DArP conditions were
optimized allowing for the exclusion of defects (α, β, and δ), allowing for the application
of these conditions to polymers with a greater potential for β-defect formation
(PPDBTTPD). (b) Depiction of the directing group effect of the ester on PDCBT
forming PDCBTβ, and the suppression or enhancement for β-defect formation when
biaryls with different β-protons (PDCTT and PDCBTz) are used compared with PDCBT.
74

and PPDBTTPD), neodecanoic acid (NDA) inhibits β-defect formation by sterically shielding the
β-protons (Hβ1-Hβ4) from the Pd-catalyst.
69
Since NDA is present (1 equiv.) in the DArP conditions
reported here, β-defect formation must either be overcoming the steric hindrance or displacement
of the NDA coordinated to Pd by the ester moiety is occurring. Esters, specifically, have been
shown by Yu et al. to allow for the C-H activation of distal protons, via a seven-membered
cyclopalladation, on electron rich arenes.
43
In the aforementioned study, the ester moiety displaced
the carboxylic acid ligand used, allowing for C-H functionalization to occur. This type of reactivity
is analogous to what we propose for PDCBT. Specifically, the ester directing group likely
displaces the NDA and then the palladium metal center can form a seven-membered palladacycle
with the adjacent thiophene aryl group (Figure 3.2b), which is based on the findings by Yu’s
aforementioned study. While directing groups (not carbonyl based) have been used in the synthesis
of conjugated polymers via DArP, this mechanism of defect formation has not been explicitly
observed to our knowledge.
70

3.4 Synthesis of PDCTT and PDCBTz via DArP
As mentioned prior, the primary method for preventing β-defect formation in DArP is the
use of a bulky carboxylic acid, such as NDA, but if carbonyl groups along the backbone can
displace NDA then defect formation can occur. Applying the conditions then to a more reactive
bithiazole (BTz) and less reactive thienothiophene (TT) monomer would offer insight regarding
how β-proton reactivity effects the propensity for defect formation (Figure 3.2b). Using these
monomers for their respective copolymer synthesis, we expect to see an enhanced or
uncontrollable level of defects with BTz and a suppression of such defects with TT relative to BT.
Describing BTz and TT as more and less reactive towards β-defect formation is based on
previous studies in DArP and small-molecule C-H activation. Specifically, based on the
75

previous studies by Leclerc et al. regarding the Gibbs free energy (ΔG
‡
298K) associated with C-H
bond cleavage at the concerted metalation deprotonation (CMD) transition state (TS), the reactivity
of β-protons for BTz (ΔG
‡
298K = 26.7 kcal) should be greater than that of BT (ΔG
‡
298K = 28.3
kcal).
41,71
This type of calculation has not been performed for TT. However, low-reactivity for TT
has been observed, where no polymerization proceeded via DArP unless a substituted TT was used
to enhance its reactivity.
72
Furthermore, previous studies regarding the C-H activation of
thieno[3,2-b]thiophene have concluded that Pd-catalysed oxidative conditions, which differ
greatly from the ones employed here, are required for activation of the HβTT proton (Figure 3.2b),
and that conditions reliant on the pKa of the proton, such as the ones employed for this study, do
not provide coupled products in HβTT position.
73–75
In addition to a diminished reactivity, studies
on the conformation of a TT unit flanked by carboxylate containing thiophenes, such as with
PDCBT and PDCTT, have shown that twisting along the conjugated backbone occurs in the case
of TT where BT is considered to be coplanar.
76
This twisting, which may be due to steric
congestion brought upon by the more compact structure of the TT ring, leads to a large dihedral
angle (>60°), which may inhibit formation of the seven-membered palladacycle intermediate
(PDCBTβ, Figure 3.2b). Since BTz is structurally and spatially similar to BT, it is presumed that
backbone twisting will not occur and that it should possess a nearly coplanar conformation as with
PDCBT.
Confirming the ideas above, when the DArP conditions (Entry 4 of Table 3.1) that led to
gelation with PDCBT were applied to PDCTT, we found that the polymerization mixture did not
gel after 2 hours (Entry 8 of Table 3.1), and so the polymerization was left to go overnight (16
hours). After purification, it was found that the PDCTT obtained from this reaction provided a
greater Mn (26 kDa) and yield (90%), relative to the same conditions for PDCBT. It should be
76

noted that no CHCl3-insoluble material was left-over after Soxhlet purification. It is likely that the
extended reaction time contributes to the increase in yield and Mn, relative to PDCBT.
47
These
results demonstrate that a monomer relatively with inert β-protons, compared to BT, can be
employed when directing groups are present within the copolymer to successfully afford the
desired copolymer.
When 2,2’-bithiazole was used, a reactivity for this monomer like that of bithiophene was
observed. Specifically, onset of gelation of the reaction mixture was observed after 70 minutes
leading to oligomeric material (Mn of 4.9 kDa with a yield of 46%) that could be isolated in the
CHCl3 fraction of the Soxhlet (Entry 9 of Table 3.1), but with a small portion that was
prohibitively insoluble in the chloroform fraction of the Soxhlet. In order to see if a more soluble
polymer product could be isolated with a decreased reaction time, as was observed with PDCBT,
the polymerization was repeated but was stopped at 60 minutes (Entry 10 of Table 3.1). This
afforded an oligomeric product that was entirely soluble in the CHCl 3 fraction of the Soxhlet (Mn
of 3.4 kDa and 54% yield) with an improved yield albeit lower molecular weight. Based on these
results, it is clear that the reaction conditions, which affords isolable polymer products for PDCBT
and PDCTT with good molecular weights and yields, are not optimal or controllable for a more
electron deficient monomer prone to activation of the β-proton, such as bithiazole. C-H activation
of this proton (HβBTz, Figure 3.2b) is presumed to be highly favourable, and as the concentration
of the monomers decreases in the reaction mixture defect formation, such as crosslinking and
branching, will likely become more favourable. This would make cross-linking or β-couplings
highly competitive relative to the desired coupling for PDCBTz, leading to insoluble materials
before polymer products of desirable molecular weights and yields can be obtained, as with
PDCTT.
77

Although somewhat intuitive, this correlation between structure and reactivity provides a
general guide for in applying this methodology towards the synthesis of other copolymers.
Specifically, electron deficient monomers used in concert with directing groups may invoke
undesired couplings when protons that can undergo C-H activation are within a reasonable
proximity. Based on these results, it is presumed that this type of directing group effect is possible
with PDCBT, causing the activation of undesired protons and leading to the observed gelation
during the polymerization. The NMR spectra for all of the synthesized polymers is provided in
Appendix B and referenced to polymers of known structure, but
1
H-NMR is not a general method
for determining the presence of β-defects. Therefore, we confirm their presence using GIXRD and
UV-vis absorption spectroscopy.
3.5 GIXRD and UV-vis Characterization of Polymer Films
The inclusion of β-defects within a conjugated polymer backbone has pronounced effects
on the thin-film structural and electronic properties. As a consequence of the disorder caused by
the β-defect, coherent, periodic structure can be disrupted since ideal alignment of the polymer
chains is inhibited by the inclusion of a defect. This can be observed, as mentioned previously,
using GIXRD and UV-vis absorption spectroscopy. With P3HT (Figure 3.2a) prepared via DArP
as an example, β-defect content as little as 0.16% can shift d100-spacing by 0.5 Å and noticeably
decrease the intensity of the vibronic shoulder and the magnitude of the absorption coefficient in
the UV-vis absorption spectrum in comparison to Stille-P3HT.
66
A similar trend is expected for
the polymer PDCBT prepared via DArP, which is expected to contain β-defects.
As depicted in Figure 3.3 and shown in Table 3.2, the semi crystallinity and photophysical
properties of the polymer thin-films vary, which can be attributed to differences in the polymer
structure, molecular weights (Mn), and inclusion of β-defects. Specifically, the PDCBT prepared
78

via Stille (Entry 1 of Table 3.2), which has a Mn of 26 kDa (Table 3.1) possess a peak absorption
(λmax) at 556 nm and an absorption coefficient (α) of 88 × 10
3
cm
-1
(Figure 3.3b), while that
prepared via the optimal DArP conditions (Entry 4 of Table 3.1), which has a Mn approximately
half that of the Stille polymer at 13.8 kDa displays a blue shifted λmax at 543 nm and an α of 73 ×
10
3
cm
-1
(Entry 2 of Table 3.2). In regards to semicrystallinity (Table 3.2 and Figure 3.3a), the
difference between the DArP and Stille PDCBT polymers is clear, with a lower degree of
crystallinity and crystallite size (13.4 versus 15.0 nm, respectively) for the PDCBT prepared via
DArP. The d100-spacing (21.3 and 20.8 Å,
Figure 3.3 (a) GIXRD diffraction patterns for the polymers PDCBT-Stille, PDCBT-DArP,
PDCTT, and PDCBTz. (b) Absorption profiles for the polymers PDCBT-Stille, PDCBT-DArP,
PDCTT, and PDCBTz.
79

Table 3.2 GIXRD and UV-vis absorbance data for PDCBT, PDCTT, and PDCBTz. aMeasured
on polymer films prepared from a 7 mg/mL chloroform solution and annealed at 150 °C for 30
minutes.
Entry
(Polymer)
Conditions Used
(Table 3.1)
λmax (nm)
a
;
α(cm
-1
)
a
d100 (Å)
a
Crystallite
Size (nm)
a
1 (PDCBT) Stille 556; 88 × 10
3
20.8 15.0
2 (PDCBT) Entry 4 543; 73 × 10
3
21.3 13.4
3 (PDCTT) Entry 8 463; 34 × 10
3
- -
4 (PDCBTz) Entry 9 529; 65 × 10
3
20.8 11.5

respectively) for these polymers is also different by 0.5 Å (Table 3.2 Entries 1 and 2). Taken as
whole, the diminished intensity of the vibronic shoulder, the reduced absorption coefficient, and
the increase in d100-spacing provide significant evidence for β-defect formation.
66
While
differences in polymer Mn could have an effect on the aborption profile, the differences are more
likely ascribed to β-defect formation, since the Mn is greater than 10 kDa for the DArP-PDCBT
(where polythiophenes are known to show saturation of their optical properties).
77
This conclusion
is also based on our past observations with DArP and Stille-P3HT, as well PPDTBT (Figure
3.2a).
66,68

In comparison to PDCBT, PDCTT (Entry 3 of Table 3.2) presents a rather featureless
absorption profile (Figure 3.3b) with a blue shifted λmax at 463 nm, similar to what has been
previously reported (λmax at 476 nm).
47
A vibronic shoulder was not expected with PDCTT since
previous reports for this polymer depict a featureless absorption profile for the polymer prepared
via Stille.
47
As discussed above, the diminished value for α (34 × 10
3
cm
-1
) indicates a more
disordered structure for this polymer, where orbital overlap of the π-system along the polymer
backbone and the π-π interactions between polymer chains may be hindered due to twisting caused
by steric-hindrance between the alkyl chains on the accepter unit.
76
Also, no diffraction was
observed in the GIXRD measurements for this polymer further. As shown with previous studies,
this is likely because temperatures in excess of 150 °C will be needed to induce crystallization and
80

aggregation.
47,49
However, optimization of the thin-film morphology is not a focus of this study.
Given that gelation did not occur with PDCTT and no insoluble material was observed after
Soxhlet with CHCl3, it is believed that presence of β-defects is highly minimized, if not excluded,
for this polymer.
PDCBTz (Entry 4 of Table 3.2) shows an absorption profile similar to that of PDCBT
(Figure 3.3b), with the appearance of a weak vibronic-shoulder and a λmax at 529 nm (Figure 3.3b).
It is notable that despite the more-electron deficient bithiazole unit being employed for this
polymer, the blue shift for the polymer is rather slight (14 nm) versus the 80 nm observed for
PDCTT. This provides further indication of how the donor unit for this class of polymers
influences the planarity and orbital overlap of the π-system along the polymer backbone and the
π-π interactions between polymer chains. In regards to semicrystallinity, PDCBTz (Entry 4 of
Table 3.2) has a lamellar spacing of 20.8 Å, which is identical to the Stille-PDCBT polymer.
However, the reduction in crystallite size, coupled with the weak vibronic shoulder in the UV-vis
spectrum (Figure 3.3b), indicates that the PDCBTz isolated via DArP contains β-defects as was
observed for PDCBT. These results provides evidence for the hypothesis that branching or cross-
linking can be controlled by employing an electron-rich monomer that is more resilient against
crosslinking or β-defect formation, such as TT. As described above, β-defect formation is
supported when all the factors are taken into account. Specifically, in the synthesis of PDCBT and
PDCBTz via DArP (see Table 3.2 for conditions) both lead to insoluble material, which is a major
indication of a polymer laced with defects.
1
H-NMR confirms that δ-homocouplings, which could
lead to insoluble material, are not occurring. GIXRD shows a reduction in the degree of
crystallinity and a shift in the d-spacing consistent with β-defect formation. The UV-vis absorption
profiles also show a reduction in the vibronic shoulder and the absorption coefficient. All of these
81

pieces of evidence point to the likelihood of β-defect formation for the polymers PDCBT and
PDCBTz, which leads to the formation of insoluble material during the polymerization.
3.6 Conclusion
In this study we presented the application of the sustainable solvents CPME and anisole
towards the synthesis of PDCBT and its analogues, PDCTT and PDCBTz, via DArP. We find the
diester moieties on the acceptor unit can function as directing groups enhancing the reactivity of
the monomer designated for C-H bond functionalization providing a significant reduction in the
polymerization time. This enhancement in reactivity comes at the cost of selectivity, however,
since crosslinking or β-defect formation occurs leading to the formation of insoluble polymer
products. This likely occurs through displacement of the NDA, which is used to suppress β-defect
formation, from the palladium catalyst by the ester. Through careful optimization, we were able to
develop DArP conditions that allowed for the synthesis of isolable PDCBT in less than one hour,
when CPME is used as the solvent, with a molecular weight (Mn) of 13.8 kDa and a yield of 59%.
Application of the optimal conditions towards the relatively electron rich, PDCTT, which contains
thieno[3,2-b]thiophene, and electron deficient, PDCBTz, which contains 2,2’-bithiazole, was
performed to investigate the occurrence of defect formation by varying the aryl group. Specifically,
electron deficient monomers may invoke cross-linking or branching defects due to the higher
reactivity of the protons in the conjugated backbone of the polymer, which was observed with
PDCBTz. However, with the electron-rich PDCTT a polymer product with a Mn of 26 kDa and a
yield of 90% was obtained. Characterization using GIXRD and UV-vis absorption spectroscopy
confirmed the presence of β-defects in PDCBT and PDCBTz prepared via DArP. This
demonstrates an important need for understanding functional group tolerance and a guiding
principle when developing conditions for DArP. Based on our results, a directing group can
82

facilitate C-H activation of distal protons on adjacent aryl groups forming undesired defects,
despite use of a bulky carboxylic acid ligand (NDA). Suppression of such defects is possible
through the judicious selection of a comonomer, which contains a β-proton of low reactivity or
can inhibit the formation of the intermediate metallocycle. Future work will focus on determining
conditions that allow for the defect-free synthesis of electron deficient of conjugated copolymers,
such as PDCBTz, using sustainable solvents, and determine conditions that allow for a more
controlled synthesis when directing groups are employed.

83

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95

Chapter 4: Copper Catalyzed Synthesis of Conjugated Copolymers using Direct Arylation
Polymerization

4.1 Introduction
Conjugated polymers are transformative materials finding a seemingly unlimited number
of potential applications, including: organic light emitting diodes (OLED), organic photovoltaics
(OPV), electrochromics, transistors (OFET), chemical sensors and biomedical roles.
1–4
Direct
arylation polymerization (DArP) has allowed for the preparation of conjugated polymers through
C-H activation.
5,6
This methodology greatly streamlines synthetic routes and eliminates the use of
toxic, pyrophoric reagents often employed to prepare monomers for other methods of
polymerization, e.g. Stille, Suzuki, Negishi, and Kumada. Through careful investigation and
modification of the polymerization conditions, DArP can prepare polymers with undetectable
levels of homo-coupling or branching (β) defects, allowing for the defect free synthesis of a variety
of conjugated polymer architectures, including: homopolymers, donor-acceptor copolymers, semi-
random copolymers, random copolymers, and porous polymers.
7–11
This broad range of scope has
placed DArP on-par with the conventional aryl-aryl cross-coupling polymerization methodologies
listed above.
The vast majority of DArP methodologies are reliant on precious metals, such as palladium.
While Pd provides access to very robust catalysts, allowing for a broad substrate scope, relatively
mild conditions, and low catalyst loading, the high cost, low abundance, and relative toxicity make
this metal unsustainable.
12,13
Finding a suitable replacement for Pd, using a first-row transition
metal, such as Cu or Ni, would allow DArP to further its quest as a sustainable, low-cost alternative
to other aryl-aryl cross-coupling polycondensations. While there are reports of oxidative direct
96

arylation polymerizations (Oxi-DArP) using catalytic quantities (10-20 mol%) of Cu(OAc)2
affording high molecular weight (Mn) polymer products (20-45 kDa) with good yields (85-98%),
these methods require a stoichiometric oxidant and they are specific to the synthesis of
homopolymers.
14,15
This limits the scope for these conditions to overtake current Pd-catalyzed
methods that allow for copolymer synthesis with well-defined polymeric structures. Thus, a
method employing a copper catalyst that allows for aryl-aryl cross coupling to ultimately yield
conjugated copolymers, such as perfectly alternating donor-acceptor or semi-random
architectures, has eluded discovery.
Daugulis et al., Miura et al., and others have reported the Cu-catalyzed aryl-aryl cross-
coupling for various iodinated arenes and electron-deficient heterocycles, yielding bi-aryl small
molecules.
16–19
Methods developed by Daugulis et al. were able to achieve cross-coupled products
in high yields with mild bases and a low-cost Cu-phenanthroline catalyst using catalytic amounts
of the copper catalyst (10 mol %). We were therefore interested in expanding these conditions
towards the synthesis of perfectly alternating donor-acceptor conjugated copolymers, and we
chose thieno[3,4-c]pyrrole-4,6-dione (TPD) because of its prevalence in conjugated polymers
(Scheme 4.1).
While seemingly straightforward, this undertaking is not necessarily a direct transition
from small molecule to conjugated polymer synthesis. Specifically, the original conditions used
high concentrations, unfavorable solvents for conjugated polymer synthesis, and bases not
commonly found in DArP, e.g. lithium alkoxides. These conditions could be problematic due to
97

solubility issues of the growing polymer chain and chemoselectivty when applied to electrophilic
substrates commonly used for conjugated polymer synthesis.
Through optimization of the conditions on a model system, shown in Scheme 4.1 with
polymer P1, we were able to find a satisfactory condition set to apply to a broader substrate scope,
allowing for the synthesis of conjugated copolymers with good Mn (4-10 kDa) and yields (30-
97%) using low-cost, commercially available reagents. The intention of this study is to illustrate
the first step toward the broad scope synthesis of conjugated polymers via C-H activation without
noble metals, such as Pd. Listed in Table 4.1, a variety of conditions were applied towards the
synthesis of P1 (Scheme 4.1) to optimize the molecular weight (Mn) and yield, with the polymers
characterized using
1
H-NMR spectroscopy and SEC. Complete details of the monomer synthesis,
polymer synthesis, and characterization are available in Appendix C. Also, a complete listing of
the conditions explored is provided in Table C.1 of Appendix C. The polymerizations were
conducted in a sealed high-pressure vessel under a N2 atmosphere. After the allotted reaction time,
the mixtures were precipitated into a cold 10% NH4OH solution in MeOH, filtered, and washed
with water, methanol, acetone, and hexanes. No insoluble material was obtained, which would
indicate high levels of branching or structural defects embedded in the polymer chain, and the
1
H-
NMR spectrum (see Appendix C) shows agreement with the proposed structure via integration of
the aromatic (8.27-7.76 ppm) and the methylene protons alpha- to the imide nitrogen (3.71-3.58
ppm).
11

Scheme 4.1 Optimization of the synthesis of P1 using Cu-catalyzed DArP.
98

4.2 Results and Discussion
Table 4.1 Synthesis and optimization of P1 using Cu-catalyzed DArP. All reactions listed used
K2CO3 (4 equiv.) unless otherwise noted.
Entry Ligand
a
Cat. Mol
b
% Solvent
c
Temperature
(°C)
Time
(h)
Mn (kDa)
d
,
Ð
d

Yield
d

(%)
1 phen 50 DMA 140 72 5.6, 2.20 23
2 phen 50 DMF 140 72 2.4, 1.53 46
3 phen 50 DMA 166 72 4.2, 2.85 29
4 phen 50 DEA 140 72 5.4, 1.56 37
5 dmby 50 DMA 140 72 2.6, 1.68 24
6 phen 5 DMA 140 88 2.9, 1.62 15
7 phen 25 DMA 140 88 3.7, 2.13 49
8
e
phen 50 DMA 140 48 8.2, 1.64 14
f

a
Phenanthroline (phen), 4,4’-dimethyl-2,2’-bipyridine (dmby).
b
Loading based on equivalents to
each monomer. 99.999%-Puratrem Cu(I) iodide was used as the copper source with a 1:1 ratio to
the ligand.
c
N,N-dimethylacetamide (DMA), N,N-diethylacetamide (DEA); concentration for
monomers was 0.1 M for all polymerizations.
d
Determined for polymer products after purification
and collection in hexanes.
e
40 equiv. of K2CO3 were used.
f
Isolated from the filter directly after the
hexanes wash.
We fixed the catalyst loading at 50 mol % for the conditions studied in Table 4.1 because
the concentration for our polymerizations (0.1 M) were much more dilute relative to those for Cu-
catalyzed small-molecule synthesis (1 M), although lower loadings (5, 25%) did generate polymer
product (entries 6, 7). We found that the selection of base, solvent, and the catalyst ligands were
critical in the synthesis of P1. Of the bases studied (Cs2CO3, Na2CO3, and t-BuOLi in Table C.1
of Appendix C), only K2CO3 was found to provide polymer product. This is likely due to a balance
between basicity, solubility, and chemoselectivty with K2CO3, given that no reaction was observed
aside from t-BuOLi, which lead only to visible decomposition of the substrates and no polymer
product (Table C.1).
Highly-polar amide solvents, which possess a strong basicity and coordinating ability, such
as N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMA) were found to be
essential for polymer synthesis (entries 1 and 2), with DMA providing a satisfactory Mn of 5.6 kDa
and yield of 23% (entry 1). Raising the temperature from 140 °C to 166 °C (entry 3) did not provide
99

an improve-ment in Mn (4.2 kDa), although the yield slightly increased (29%). Replacing DMA
with N,N-diethylacetamide (DEA) (entry 4) did provide a similar value for Mn (5.4 kDa) and
improved yield (37%), relative to entry 1. However, DEA is cost prohibitive compared to DMA
making its general application for conjugated polymer synthesis less appealing. Highly-polar
amide solvents are required likely due to the limited solubility of the copper catalyst and the base
in other organic solvents, and it is also possible that the solvent assists in the deprotonation step
based on other studies regarding solvent-basicity and C-H activation (Figure C1 in Appendix
C).
20,21
Solvent mixtures, such as DMF and chlorobenzene (CB), were found to hinder the
polymerization leading to no isolable polymer product, owing to the importance of high-solvent
polarity and basicity for these conditions (Table C.1).
While various ligands have been explored for copper catalyzed direct arylations in previous
studies, we were interested to see how the ligand influenced the outcome of the polymerization.
We found that phenanthroline provided the best results in comparison to 1,1’-
bis(diphenylphosphino)ferrocene (dppf) (Table C.1), 4,4’-dimethyl-2,2’-bipyridine (dmby) (entry
5), and neocuproine (Table C.1), where aside from phenanthroline only dmbpy provided polymer
product albeit with lower Mn (5.6 versus 2.6 kDa, respectively). Phenanthroline’s optimal
performance as a ligand is likely attributable to its strong binding to copper and low-level of steric
hindrance near the metal center. This confirms the findings of others, and provides an easily
obtained catalyst from relatively bench-stable, low-cost constituents.
16,22
Lowering the catalyst
loading to 25 and 5 mol % provided satisfactory results after optimizing the solvent, ligand,
temperature, and base (entries 6 and 7, respectively), although the values for Mn decreased relative
to entry 1 (2.9 and 3.7 kDa versus 5.6 kDa, respectively). However, these results do show that this
methodology is compatible with lower catalyst loadings, although longer polymerization times are
100

likely required to achieve comparable Mn to higher loadings. While Daugulis et al. were able to
achieve lower catalyst loadings (10 mol %) for the synthesis of small-molecule biaryls, the
concentration was significantly higher (1 M) and the bases more reactive (t-BuOLi), which are not
amenable to conjugated polymer synthesis due to solubility and chemoselectivity issues.
16

Although many DArP protocols use higher concentrations (>0.1 M) more favorable for
polycondensation reactions, the low solubility of P1 in polar, amide solvents, as evidenced by its
precipitation from the reaction mixture at low molecular weights, inhibited this.
5,6

In attempts to further increase the Mn of P1 from 5.6 kDa (entry 1), we increased the
equivalents of base. While the other entries of Table 4.1 used 4 equivalents of K2CO3, based on a
report by Leclerc et al. we found that an extreme excess of base (40 equivalents, K2CO3) afforded
the highest value for Mn for P1 (8.2 kDa), likely helping to facilitate C-H activation (entry 8).
23

Although soluble in CHCl3 and DCB, the collected polymer product for entry 8 was insoluble in
hexanes, where entries 1-7 were collected in the hexanes wash. This is likely why the yield for
entry 8 is low relative to entries 1-7, since the hexanes soluble fraction of entry 8 was not included
in the calculation of overall yield. Also, the reaction time is less for entry 8 (48 versus 72 hours),
since the amount of precipitate present in the reaction mixture reached a qualitatively higher level
than the other entries after only 48 hours. Given the result of 8.2 kDa for entry 8, we felt that near
optimal conditions were in hand for broadening the scope to other substrates.
Provided in Table 4.2, conditions derived from the optimization of the synthesis of P1
(entries 1 and 8 in Table 4.1) were applied to a series of aryl-donors (3-6) and TPD acceptors with
varying alkyl substituents (Scheme 4.2). The partitioning of Table 4.2 is based on the solvent
fraction that the polymer product was collected for the same reaction (fraction 1 or fraction 2),
either acetone, hexanes, or off the filter directly, where the Mn, Ð, and yield are listed for each
101

respective fraction, along with the overall yield for combined fractions. As with P1, all polymers
(P2-P7) were soluble in organic solvents, i.e. indicating an absence of undesired defects embedded
in the polymer chain. Replacement of the phenylene donor of P1 with thiophene (P2a) provided a
polymer product with similar Mn (8.8 kDa) and yield (30%) when 4 equivalents of K2CO3 were
used (versus 5.6 kDa and 23% yield for P1) However, when 40 equivalents of K 2CO3 were used
(P2b) the Mn and yield decreased (5.5 kDa, 4%). This trend was also observed for P3, P4, and P5,
where increasing the equivalents of base led to lower yield and Mn (P2b-P5b). It should be noted
no polymer product was obtained for P3 when 40 equivalents of base were used, which is
why this entry is excluded from the Table 4.2. It is believed sensitivity to the amount of base could
be due to lower polymer solubility in a highly polar reaction medium, leading to premature
precipitation of the polymer, given that P2 is a polymer possessing low-solubility outside of
chlorinated solvents (as evidenced by Marks et al.)
24
and that P3 possesses a polymer structure
more amenable to non-polar media (as evidenced by Ozawa
et al.).
25
Inclusion of a dialkoxy phenylene donor (4), providing P3, gave a satisfactory yield of
43% (P3a). However, it is believed the bulky alkyl chains, caused steric hindrance near the Cu-
Scheme 4.2 Synthesis of polymers P2-P7 using conditions derived from Table 4.1.
102

Table 4.2 Results of the copolymerizations for the monomers depicted in Scheme 4.2, including:
molecular weights (Mn), Ð, and yield.
Polymer
a,b
Equiv.
of
K 2CO 3
Fraction
1
M n
(kDa)
a
;
Ð
Yield
(%)
a
Fraction
2
M n
(kDa)
a
;
Ð
Yield
(%)
a
Overall
Yield
(%)
a
P2a 4 - - - hexanes
insoluble
8.8;
2.36
30 30
P2b

40 - - - hexanes
insoluble
5.5; 2.9 4 4
P3a

4 acetone 3.2;
1.36
22 hexanes 5.0;
1.37
21 43
P4a

4 - - - hexanes
insoluble
10.1;
1.86
55 55
P4b 40 hexanes 2.3;1.31 10 hexanes
insoluble
3.9;
1.30
6 16
P5a

4 hexanes 5.6;
3.17
71 hexanes
insoluble
5.9;
3.11
22 93
P5b 40 hexanes 3.55;
1.82
34 - - - 34
P6a

4 hexanes 4.8;
1.83
3 - - - 3
P6b

40 hexanes 4.4;
1.74
40 hexanes
insoluble
9.7;
1.44
7 47
P7b

40 hexanes 5.4;
2.49
97 - - - 97
a
Measured after polymer purification.
b
Polymerizations with 4 equivalents of K2CO3 are denoted
with “a”, while 40 equivalents is denoted with “b”.
metal center, and unfavorable solubility of this polymer in polar amide solvents caused the
premature precipitation of P3, leading to lower than expected values for Mn in the acetone wash
(2.9 kDa) and the hexanes wash (5.0 kDa) relative to P1.
Inclusion of alkyl fluorene donors provided the highest values for Mn and yield (P4-P7)
compared to P1-P3. P4, which has hexyl substituents on the fluorene, provided the highest M n
(10.1 kDa) for polymers P1-P7 and a good yield (55%). Incorporation of a bulkier alkyl chain on
TPD, 2-decyltetradecyl, gave a lower value for Mn (4.1 kDa) in fraction 2 relative to P4, but the
overall yield for P5 is much higher (93% versus 55%, respectively). The octyl substituted fluorene
(6) afforded satisfactory Mn (9.7 kDa) for fraction 2 with 40 equivalents of base (P6b). These
103

conditions were then replicated for P7, which incorporates 2-octylnonyl TPD. This gave a lower
Mn than P6b (5.4 kDa versus 9.7 kDa), but the overall yield was significantly improved and the
highest reported for this study (97%). Given the sensitivity to sterics and solubility observed for
the fluorene-TPD copolymers P4-P5, the 2-octylnonyl TPD was selected over 2-decyltetradecyl
for P7. It should be noted that the bromide analog of 6 did not provide any reaction, indicating the
potential need for the higher reactivity of an aryl-iodide.
To assess potential structural defects within the polymer,
1
H-NMR spectroscopy was
employed and the spectra for known polymers P2-P7 was referenced to literature spectra, which
were collected under the same conditions. Defect analysis was performed by referencing to the
known homopolymers or homocoupled biaryls for each of the synthesized polymers in order to
determine a major presence of donor-donor (δ), acceptor-acceptor (α), or branching defects (β)
present in the aromatic region. End-group assignments are illustrated in Figure 4.1, and are based
on known polymers and model compounds with similar structure to that of the synthesized
polymers.
25–32
For P3, the major resonance found corresponds to that of the desired polymer
structure based on literature precedent (δ8.32).
25
The spectrum also indicates that potential defects,
including α-defects (δ7.89) and δ-defects (δ7.10), are not an observable feature as the
Figure 4.1
1
H NMR of P3 (top) and P4 (bottom) with sites for end-groups, acceptor-acceptor (α),
donor-donor (δ), and branching defects (β) based on homocoupled products denoted. Conducted
in CDCl3 at 25 °C.
104

corresponding resonances are not apparent.
33,34
For P4, the major resonances correspond to that of
the desired copolymer (δ8.27-8.23 and δ7.86 ).
26
Resonances which would indicate high levels of
homocoupling defects, such as α-defects (δ7.89), δ-defects (δ 7.88), and β-defects (δ 7.45), were
not observed.
32,34,35

4.3 Conclusion
In summary, the first report of a methodology for perfectly alternating donor-acceptor
conjugated polymer synthesis was developed that uses Cu-catalyzed DArP, offering an initial step
towards the replacement of noble metals, such as Pd. Conjugated polymers were prepared in good
yields (up to 97%) and Mn (up to 10 kDa). The recovered polymer product was soluble in organic
solvents and characterized using NMR spectroscopy, which indicates an absence or minimization
of undesired couplings. Future work will seek to explore the substrate scope for the given condition
set, decrease catalyst loadings, and find more mild conditions by exploring different copper
catalysts and polymerization conditions.

105

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111

Chapter 5: Sustainable Synthesis of a Fluorinated Arylene Conjugated Poly-mer via Cu-
Catalyzed Direct Arylation Polymerization (DArP)

5.1 Introduction
Conjugated polymers have become promising for a wide variety of applications, ranging
from optoelec-tronic devices to biomedical applications. Conventionally, their synthesis has relied
on cross-coupling methods that often invoke toxic, hazardous reagents and extend-ed synthetic
routes. Through direct arylation polymerization (DArP), their synthesis has become simplified,
and many of the hazards associated with conjugated pol-ymer synthesis can be circumvented
through the use of C-H activation.
1–5
DArP, however, still relies on unsustainable metal catalysts,
such as Pd, which hinders the effort towards greater sustainability that DArP seeks to address.
Other efforts to improve the sustainability of DArP have remained limited.
6,7

As an effort to employ more sustainable transition metal catalysts, such as copper,
oxidative coupling has become a successful method for conjugated polymer synthesis, but these
methods are restricted to the preparation of homopolymers and require a stoichiometric amount of
oxidant.
8,9
Methods for copper-catalyzed aryl-aryl cross couplings using C-H activation are
known, but their application towards perfectly alternating conjugat-ed copolymer synthesis has
only just come under investigation. As the first report, we have previously disclosed conditions for
the Cu-catalyzed DArP of various thieno[3,4-c]pyrrole-4,6-dione (TPD) copolymers, and we
became interested in expanding the scope of this methodology to other substrates.
10
We had
postulated that the carbonyls on TPD can function as a directing group, helping to facilitate C-H
112

functionalization, and thus we were determined to know whether or not Cu-DArP is compatible
with substrates that do not possess this type of functionality.
Daugulis et al. have reported the synthesis of biaryls through the cross-coupling of a
fluoroarenes and an aryl iodide.
11,12
This method requires only a mild base, such as K3PO4, and is
suitable for catalytic amounts of the copper catalyst (10 mol %). Given these parameters, we were
interested to extend this methodology towards the synthesis of conjugated polymers, in an effort
to show that copper catalysts can potentially replace Pd-catalysts in DArP. Transcribing these
conditions for conjugated polymers is not direct, however, since Dau-gulis originally used high-
concentrations (1 M) and a stoichiometric imbalance between the cross-coupling partners.
Conditions such as these are not favorable for conjugated polymer synthesis, since conjugated
polymers typically possess low-solubility and require an accurate stoichiometric balance to
achieve high molecular weights (Mn).
5.2 Results and Discussion
Shown in Scheme 5.1, our efforts have focused on optimizing the synthesis of poly[(9,9-
dioctylfluorene-2,7-diyl)-(2,2′,3,3′,5,5′,6,6′-octafluoro-4,4′-diphenylene)] (PDOF-OD), which has
been previously prepared using Pd-catalyzed DArP.
13,14
The focus of optimization was in regards
to catalyst loading, where the equivalents of base, catalyst loading, ligand, and solvent
concentration, were varied as detailed in Table 5.1.

Scheme 5.1 Synthesis of PDOF-OD using the conditions outlined in Table 5.1.
113

Table 5.1 Optimization of Cu-DArP conditions for PDOF-OD.
Entry Cat.
Mol
a
%
Base (eq.) Solvent
b
(M) Temp.
(°C)
Time (hr.)

M n (kDa)
c
, Ð
c
Yield
c
(%)
1 50 K 2CO 3 (4) DMA (0.1) 140 72 10.1, 2.16 64
2 50 K 2CO 3 (40) DMA (0.1) 140 72 - 0
3 50 K 3PO 4 (4) DMA (0.1) 140 72 24.5, 2.18 78
4 50 K 3PO 4 (40) DMA (0.1) 140 72 insoluble 64
5 25 K 3PO 4 (4) DMA (0.1) 140 72 4.3, 2.62 72
6 15 K 3PO 4 (4) DMA (0.1) 140 72 2.7, 2.56 52
7 5 K 3PO 4 (4) DMA (0.1) 140 72 1.46, 1.91 48
8 15 K 3PO 4 (40) DMA (0.1) 140 72 - 0
9 5 K 3PO 4 (40) DMA (0.1) 140 72 - 0
10 15 K 3PO 4 (4) DMA (0.5) 140 16 20.4, 3.18 71
11 5 K 3PO 4 (4) DMA (0.5) 140 16 6.79
d
, 51
12 5 K 3PO 4 (4) DMA (0.25) 140 16 16.4, 2.23 54
13 5 K 3PO 4 (4) DMA (0.5) 120 16 4.67, 5.20 36
14 5 K 3PO 4 (4) DMA (0.25) 140 36 insoluble

62
a
Loading based on equivalents to each monomer. 99.999%-Puratrem Cu(I) iodide was used as the
copper source with a 1:1 ratio to phenanthroline.
b
N,N-dimethylacetamide (DMA).
c
Determined
for polymer products after purification.
d
The polymer product was only soluble in hot 1,2-
dichlorobenzene (DCB) causing much of the higher-Mn portions of the sample to be filtered-off
be before measurement using GPC.
Complete synthetic details in regards to the synthesis for monomers and polymers can be
found in Appendix D. Briefly, polymerizations were performed in a high-pressure vessel under
N2 atmosphere for the allotted reaction time and temperature. The reaction mixture was then
cooled, solids were dissolved in hot 1,2-dichlorobenzene, and then precipitated into a cold 10%
(v:v) ammonium hydroxide/methanol solution. The polymer was then filtered off and washed
sequentially with water, methanol, acetone, and hexanes. The polymer was then collected and dried
overnight under high-vacuum. Based on our previous study with TPD Cu-catalyzed DArP, for the
synthesis of PDOF-OD (Scheme 5.1) we initially employed K2CO3 as a base (4 equivalents), CuI
as the copper source (50 mol%), phenanthroline (phen) as the ligand (50 mol%), N,N-
dimethylacetamide (DMA) as the solvent, at 140 °C for 72 hours (Entry 1).
10
We found this
provides a good value for Mn (10.1 kDa) and yield (64%). Adding an excess of base (40 equiv.,
114

Entry 2), was detrimental to the reaction and no polymer product was afforded, despite being a
successful strategy for promoting C-H functionalization in our previous study and a report on Pd-
catalyzed DArP by Leclerc et al.
10,15
Since Daugulis et al. had success employing K3PO4 as a base
for certain substrates, we figured this might be an improvement over K2CO3. Indeed, as shown in
Entry 3, K3PO4 as a base provided a significant increase in Mn and yield (24.5 and 78%,
respectively) relative to Entry 1. This demonstrates the capacity for these conditions to yield
perfectly alternating conjugated co-polymers, without the need for a directing group to help
facilitate C-H functionalization. Increasing the equivalents of K3PO4 to 40 equivalents only
afforded insoluble polymer product with a slightly diminished yield (64%, Entry 4). Given the
high catalyst loading (50 mol%) in addition to the high equivalents of base for Entry 4, we presume
the insolubility of the polymer product is likely due to a Mn that is too high to allow for solubility
in 1,2-dichlorobenzene (DCB).
With optimal conditions for 50 mol% catalyst loading, we sought to probe lower loadings
(Entries 5-7). A significant decrease in Mn was observed (4.3 kDa) for 25 mol% (Entry 5), but the
yield remained similar to that of Entry 3 (72%). A similar trend was observed for lower loadings
(15 and 5 mol%), where the value for Mn significantly diminished, while the yield remained
moderate (entries 6 and 7). Interestingly, no polymer product was obtained when higher
equivalents of base (40 equiv.) was employed with a lower catalyst loading (Entries 8 and 9).
Taking into account the results from Entries 5-9, we presumed that the concentration of the
monomers is too low (0.1 M), which is generally unfavorable for step-growth polymerizations
such as the one under study. Since the solubility of the PDOF-OD polymer is reasonable in DMA,
as evidenced by the value for Mn with Entry 3 (24.5 kDa), we envisioned that increasing the
concentration of the reaction mixture from 0.1 M to 0.5 M would help to facilitate the
115

polymerization at lower catalyst loadings. As shown with Entry 10, an increase in the
concentration from 0.1 M (Entry 6) to 0.5 M with a 15 mol% catalyst loading led to a significant
increase in the value for Mn (20.4 kDa versus 2.7 kDa) and yield. The reaction time was also
decreased from 72 (Entry 6) to 16 hours (Entry 10) due to visible gelation of the reaction mixture.
This result significantly improved upon our previously disclosed conditions for Cu-catalyzed
DArP, which required higher catalyst loadings (50 mol%) and prolonged reaction times (72
hours).
10
Aside from the increase in concentration, we believe the low pKa of 2 and good solubility
of PDOF-OD also contribute to the improvement in Mn and yield. When the catalyst loading is
further lowered from 15 mol% (Entry 10) to 5 mol% (Entry 11) the solubility of the isolated
polymer product became significantly lower, presumably due to a higher Mn being achieved. The
portion of polymer soluble in DCB from this sample, allowing for measurement by GPC, gave an
Mn of 6.79 kDa and a yield of 51%.
Support for the claim that the insoluble materials obtained were consequential of a high Mn
being achieved, as opposed to branching, cross-linking, or oth-er structural defects, is provided in
the discussion regarding the
1
H (Figure 5.2) and
19
F NMR analysis below. In regards to the
polymerization reaction, in order for branching or cross-linking to occur, it would require the
activation of a C-H bond on fluorene, which is relatively not acidic. A previous study of PDOF-
OD synthesis using Pd-catalyzed DArP, suggests that branching may occur, where 1 and 2
oxidatively couple to form branched structures.
13
The conditions employed for the aforementioned
study used P(tBu)2Me·HBF4 as the phosphine ligand, DMA as the solvent, and Pd(OAc)2 as the
palladium source. It should be noted, that the ligand (P(tBu)2Me·HBF4) and solvent (DMA) may
be the cause of the observed defects, since in a subsequent study, with PCy3 as the ligand and
toluene as the solvent, branching defects were not reported.
14
For reference, in the case of Cu-
116

catalyzed oxidative couplings, Cu(OAc)2 is generally employed for substrates with greater
reactivity than fluorene, such as benzothiazole or other azaheterocycles, and those using Cu(I)
catalysts require more reactive bases.
8,9,11,16–18
For example, a study regarding copper catalyzed
dehydrogenative, or oxidative, couplings between benzothiazole and pentafluorobenzene, required
excess lithium alkoxide as a base, likely ruling out branching or cross-linking in our case.
19
Further
structural analysis using
1
H-NMR spectroscopy, discussed below, provides additional evidence for
the absence or minimization of branching with the reaction conditions reported here.
Operating under the hypothesis that the conditions in entry 11 resulted in insoluble, high
Mn polymer, the concentration was lowered from 0.5 M (Entry 11) to 0.25 M (Entry 12). This
afforded a more soluble polymer product with a Mn of 16.4 kDa and a yield of 54%. We also
attempted to achieve more soluble polymer product by lowering the reaction temperature to from
140 °C to 120 °C (Entry 13). However, this provided significantly lower Mn (4.67 kDa) and yield
(36%) for the given reaction time (16 hours). It is possible that extending the reaction time may
allow for improved Mn and yield at lower temperatures.
Characterization of the PDOF-OD polymers was performed using
1
H-NMR spectroscopy,
in order to confirm the proposed structure.
1
H-NMR data for Table 5.1 is provided in Appendix
D. As shown in Figure 5.1, the structure of PDOF-OD matches identically with that previously
reported with resonances centered at δ7.94 and δ7.59 (ppm).
13,14
The assignment of end-groups
was performed by comparing the obtained spectrum for PDOF-OD to that of model compounds
with similar structure, for which a detailed discussion is provided in Appendix D (see Section D.5
of Appendix D and Figure D.1).
13,20–23
The proposed location for the octafluorobiphenyl end-
group is slightly up-field (δ7.38) from that of the tetrafluorobenzene model compound (δ7.08), but
this is likely due to further deshielding brought upon by the additional tetrafluorobenzene group
117

attached and is close to the range of chemical shift observed for these compounds (δ 7.35-
7.27).
20,24

19
F NMR spectroscopy was also performed for structural analysis (see Appendix D for
spectra), and we observed two singlet resonances at δ-135.0 and δ-138.9, which are in good
agreement with the literature values of δ-135.0 and δ-139.0.
13,14
Minor resonances were not
observed in the
19
F NMR spectra at -134.1 ppm and -134.5 ppm, which are believed to be
associated with a terminal octafluorobiphenyl unit. Also, resonances in the range of 24-25 ppm
were not observed, which would indicate the oxidative coupling of the octafluorobiphenyl units
yielding perfluorinated oligo(p-phenylenes).
13,24

Based on a previous study, the presence of branching or cross-linking in PDOF-OD
prepared via DArP can be determined by comparing the number of repeat units calculated using
NMR spectroscopy with that from GPC.
13
Because end-groups were not observed in the
19
F
Figure 5.1
1
H NMR of PDOF-OD synthesized using the conditions outlined in Table 5.1 (Entry
3). Collected in CDCl3 at 25 °C and 500 MHz.
118

spectrum, the end-groups present in
1
H-NMR were used for the analysis. Using the
1
H-NMR
spectrum from Entry 10 as an example (Figure 5.2), integral ratios between the end group c-c’
and the polymeric protons C-C’ (annotated in Figure 5.1 and Figure 5.2) show a ratio of 1:25,
which is in close agreement with the estimate for Mn provided by the GPC (1:30). This suggests
that the potential branching defects observed using Pd(OAc)2, (P(tBu)2Me·HBF4), and DMA based
conditions are sup-pressed with the Cu-catalyzed methodology presented here, where PDOF-OD
with branching-defects are reported to have a much greater disparity between the NMR and GPC
data (1:25 versus 1:127, respectively).
13
Given that the c-c’ proton is adjacent to the b-b’ proton,
which is the proposed location for branching, any in-stance of branching would likely have a direct
effect on the integration of this resonance (c-c’). We hypothesize that this suppression of
branching-defects (β-defects) is likely due to the sensitivity of the Cu-catalyst to steric hindrance
and the general lower reactivity of the Cu-catalyst towards C-H functionalization.
10,12,25

Figure 5.2 Integral ratio between c-c’ and C-C’ protons of PDOF-OD (entry 10 of Table 5.1).
Collected in CDCl3 at 25 °C and 500 MHz.
119

5.3 Conclusion
In summary, we have presented the optimization Cu-DArP that allow for a substantial
decrease in the loading of the catalyst, from 50 mol% to 5 mol%. This was achieved through
optimization of the base employed and increasing the concentration of the monomers. Lowering
the catalyst loading is without great sacrifice to the values for Mn and yield for PDOF-OD, which
are 16.4 kDa and 54% for 5 mol% Cu-catalyst. Structural analysis of the synthesized polymers
using
1
H-NMR spectroscopy shows agreement with previously reported values and a shows a
minimization of or exclusion of defects, specifically branching caused by oxidative or
dehydrogenative couplings. Employing Cu-DArP for substrates without directing-groups
successfully demonstrates the capacity for this methodology to be applied to a broader scope.
Future work will seek to improve upon the polymerization conditions and expand the substrate
scope.

120

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(13) Lu, W.; Kuwabara, J.; Iijima, T.; Higashimura, H.; Hayashi, H.; Kanbara, T. Synthesis of
π-Conjugated Polymers Containing Fluorinated Arylene Units via Direct Arylation: Efficient
122

Synthetic Method of Materials for OLEDs. Macromolecules 2012, 45 (10), 4128–4133.
https://doi.org/10.1021/ma3004899.
(14) Saito, H.; Kuwabara, J.; Kanbara, T. Facile Synthesis of Fluorene-Based π-Conjugated
Polymers via Sequential Bromination/Direct Arylation Polycondensation. J. Polym. Sci. Part A:
Polym. Chem. 2015, 53 (19), 2198–2201. https://doi.org/10.1002/pola.27689.
(15) Grenier, F.; Goudreau, K.; Leclerc, Mario. Robust Direct (Hetero)Arylation
Polymerization in Biphasic Conditions. J. Am. Chem. Soc. 2017, 139, 2816–2824.
https://doi.org/10.1021/jacs.6b12955.
(16) Do, H.-Q.; Daugulis, O. Copper-Catalyzed Arylation of Heterocycle C−H Bonds. J. Am.
Chem. Soc. 2007, 129 (41), 12404–12405. https://doi.org/10.1021/ja075802+.
(17) Qin, X.; Feng, B.; Dong, J.; Li, X.; Xue, Y.; Lan, J.; You, J. Copper(II)-Catalyzed
Dehydrogenative Cross-Coupling between Two Azoles. J. Org. Chem. 2012, 77 (17), 7677–7683.
https://doi.org/10.1021/jo301128y.
(18) Liu, C.; Yuan, J.; Gao, M.; Tang, S.; Li, W.; Shi, R.; Lei, A. Oxidative Coupling between
Two Hydrocarbons: An Update of Recent C–H Functionalizations. Chem. Rev. 2015, 115 (22),
12138–12204. https://doi.org/10.1021/cr500431s.
(19) Fan, S.; Chen, Z.; Zhang, X. Copper-Catalyzed Dehydrogenative Cross-Coupling of
Benzothiazoles with Thiazoles and Polyfluoroarene. Org. Lett. 2012, 14 (18), 4950–4953.
https://doi.org/10.1021/ol3023165.
123

(20) Wakioka, M.; Kitano, Y.; Ozawa, Fumiyuki. A Highly Efficient Catalytic System for
Polycondensation of 2,7-Dibromo-9,9-Dioctylfluorene and 1,2,4,5-Tetrafluorobenzene via Direct
Arylation. Macromolecules 2013, 46, 370–374. https://doi.org/10.1021/ma302558z.
(21) Hernández, M. C. G.; Zolotukhin, M. G.; Maldonado, J. L.; Rehmann, N.; Meerholz, K.;
King, S.; Monkman, A. P.; Fröhlich, N.; Kudla, C. J.; Scherf, U. A High Molecular Weight
Aromatic PhOLED Matrix Polymer Obtained by Metal-Free, Superacid-Catalyzed
Polyhydroxyalkylation. Macromolecules 2009, 42 (23), 9225–9230.
https://doi.org/10.1021/ma902061t.
(22) Lu, W.; Kuwabara, J.; Kanbara, T. Polycondensation of Dibromofluorene Analogues with
Tetrafluorobenzene via Direct Arylation. Macromolecules 2011, 44 (6), 1252–1255.
https://doi.org/10.1021/ma1028517.
(23) Luo, Z.-J.; Zhao, H.-Y.; Zhang, X. Highly Selective Pd-Catalyzed Direct C–F Bond
Arylation of Polyfluoroarenes. Org. Lett. 2018, 20 (9), 2543–2546.
https://doi.org/10.1021/acs.orglett.8b00692.
(24) Heidenhain, S. B.; Sakamoto, Y.; Suzuki, T.; Miura, A.; Fujikawa, H.; Mori, T.; Tokito,
S.; Taga, Y. Perfluorinated Oligo(p-Phenylene)s: Efficient n-Type Semiconductors for Organic
Light-Emitting Diodes. J. Am. Chem. Soc. 2000, 122 (41), 10240–10241.
https://doi.org/10.1021/ja002309o.
(25) Daugulis, O.; Do, H.-Q.; Shabashov, D. Palladium- and Copper-Catalyzed Arylation of
Carbon−Hydrogen Bonds. Acc. Chem. Res. 2009, 42 (8), 1074–1086.
https://doi.org/10.1021/ar9000058.
124

Appendix A

Chapter 2: Investigation of Green Solvents for Direct Arylation Polymerization (DArP)

A.1 General
All reactions were performed under dry N2 in oven dried glassware, unless otherwise noted.
Unless otherwise noted, all reagents were purchased and used as received from commercial
sources. Solvents were purchased from VWR and used without purification, unless otherwise
noted. Anhydrous, unstabilized cyclopentyl methyl ether (CPME) was purchased and used as
received. Cs2CO3 was ground into a fine powder and dried at 120 °C in a vacuum oven before use.
Tetrahydrofuran (THF) was dried over sodium/benzophenone before distillation. 2-MeTHF was
dried over CaH2 and distilled onto activated molecular sieves (3 Å) prior to use. Diethylcarbonate
(DEC) and γ-Valerolactone (GVL) were stirred with K2CO3 and distilled onto activated molecular
sieves (3 Å) prior to use. 1,4-dibromo-2,5-bis[(2-hexyldecyl)oxy]-benzene (S1), 4,7-di-2-thienyl-
2,1,3-benzothiadiazole (S2), and 2-bromo-3-hexyl-thiophene (S3) were prepared following
literature procedures.
1–4
All NMR were recorded at 25 °C using CDCl3 on either a Varian Mercury
400 MHz, Varian VNMRS-500 MHz, or a Varian VNMR-600 MHz. All spectra were referenced
to CHCl3 (7.26 ppm), unless otherwise noted. Number average molecular weight (Mn) and
polydispersity (Ð) were determined by size exclusion chromatography (SEC) using a Viscotek
GPC Max VE 2001 separation module and a Viscotek Model 2501 UV detector, with 70 °C HPLC
grade 1,2-dichlorobenzene (o-DCB) as eluent at a flow rate of 0.6 mL/min on one 300 × 7.8 mm
TSK-Gel GMHHR-H column (Tosoh Corp). The instrument was calibrated vs. polystyrene
standards (1050−3,800,000 g/mol), and data were analysed using OmniSec 4.6.0 software.
125

Polymer samples were dissolved in HPLC grade o-dichlorobenzene at a concentration of 0.5 mg
ml−1, stirred at 65 °C until dissolved, cooled to room temperature, and filtered through a 0.2 μm
PTFE filter.
For polymer thin-film measurements, solutions were spin-coated onto pre-cleaned glass
slides from o-dichlorobenzene (o-DCB) solutions at 7 mg/mL. UV−vis absorption spectra were
obtained on a Perkin-Elmer Lambda 950 spectrophotometer. Thicknesses of the samples and
grazing incidence X-ray diffraction (GIXRD) measurements were obtained using Rigaku
diffractometer Ultima IV using a Cu Kα radiation source (λ = 1.54 Å) in the reflectivity and grazing
incidence X-ray diffraction mode, respectively. Crystallite size was estimated using Scherrer’s
equation:
τ = Kλ/(β cosθ) (1)
where τ is the mean size of the ordered domains, K is the dimensionless shape factor (K = 0.9), λ
is the x-ray wavelength, β is the line broadening at half the maximum intensity (FWHM) in radians,
and θ is the Bragg angle.
A.2 Polymer Synthesis
General procedure for PPDTBT synthesis using a high-pressure vessel:
An oven-dried 15 mL high pressure vessel equipped with a stir-bar was stoppered with a rubber-
septum and cooled under a flow of N2. S1 (0.25 mmol), S2 (0.25 mmol) Cs2CO3 (3 equiv.), and
P(o-anisyl)3 (8 mol %) were added to the vessel. The solvent was then added to the vessel via
syringe to achieve the appropriate monomers’ concentration, and it was degassed for 15 min. using
N2. Pd2dba3 (2 mol %) was then added quickly and the rubber septum replaced with a Teflon
screw-cap with a rubber o-ring. The vessel was then submerged in a pre-heated oil bath (120 °C).
126

After the polymerization, the reaction mixture was cooled to room temperature, the product was
dissolved in chlorobenzene, and then precipitated into cold MeOH. The polymer product was
filtered off and purified using Soxhlet extraction with MeOH, hexanes, and CHCl 3. The
chloroform fraction was concentrated and precipitated into cold methanol, the solid filtered off,
and then dried overnight under vacuum.
General procedure for PPDTBT synthesis using a Schlenk-tube:
An oven-dried 15 mL Schlenk-tube equipped with a stir-bar was stoppered with a rubber-septum
and cooled under a flow of N2. S1 (0.25 mmol), S2 (0.25 mmol) Cs2CO3 (3 equiv.), and P(o-
anisyl)3 (8 mol %) were added to the vessel. The vessel was then vacuum-backfilled with N2 3
times. The solvent was then added to the vessel via syringe to achieve the appropriate monomers’
concentration, and it was degassed for 15 min. using N2. Pd2dba3 (2 mol %) was then added
quickly. The vessel was then submerged in a pre-heated oil bath (120 °C). After the
polymerization, the reaction mixture was cooled to room temperature, the product was dissolved
in chlorobenzene, and then precipitated into cold MeOH. The polymer product was filtered off and
purified using Soxhlet extraction with MeOH, hexanes, and CHCl3. The chloroform fraction was
concentrated and precipitated into cold methanol, the solid filtered off, and then dried overnight
under vacuum.
Poly[(2,5-bis(2-hexyldecyloxy)phenylene)-alt-(4,7-di(thiophen-2-
yl)benzo[c][1,2,5]thiadiazole)](P1-P3).
1
H NMR (600 MHz, CDCl3, 25 °C): δ ppm 8.18 (br, 2H),
7.93 (br, 2H), 7.69 (br, 2H), 7.37 (br, 2H), 4.10 (br, 4H), 2.01 (br, 2H), 1.68 (br, 4H), 1.44−1.23
(m, 44H), 0.86−0.82 (br, 12H).
Poly(3-hexylthiophene) (P5).
1
H NMR (600 MHz, CDCl3, 25 °C): δ ppm 6.98 (s, 1H), 2.81 (t, J
= 7.8 Hz), 1.72-1.70 (m, 2H), 1.44-1.35 (m, 6H), 0.92 (t, J = 7.2 Hz, 3H).
127

A.3 Monomer NMR

Figure A.1
1
H NMR of S1 in CDCl3 at 25 °C.
128

Figure A.2
13
C NMR of S1 in CDCl3 at 25 °C.
129

Figure A.3
1
H NMR of S2 in CDCl3 at 25 °C.
130

Figure A.4
13
C NMR of S2 in CDCl3 at 25 °C.

131

Figure A.5
1
H NMR of S4 in CDCl3 at 25 °C.
132

Figure A.6
13
C NMR of S4 in CDCl3 at 25 °C.

133

A.4 Polymer NMR

Figure A.7
1
H NMR of PPDTBT (P1) in CDCl3 at 25 °C.
134

Figure A.8
1
H NMR of PPDTBT (P2) in CDCl3 at 25 °C.
135

Figure A.9
1
H NMR of PPDTBT (P3) in CDCl3 at 25 °C.
136

Figure A.10
1
H NMR of P3HT (P5) in CDCl3 at 25 °C.

137

A.5 Polymer GIXRD
Table A.1 Polymer GIXRD data.
Polymer 2θ (degrees) d100 (Å) Height FWHM (degrees) Crystallite size (nm)
P1 4.695 18.8060 7652 0.540 14.7
P2 4.653 18.9775 8673 0.518 15.3
P3 4.700 18.7844 16346 0.453 17.5
P4 4.650 18.9863 6362 0.514 15.5
P5 5.249 16.8228 14028 0.467 17.0

138

A.6 References
(1) Pankow, R. M.; Gobalasingham, N. S.; Munteanu, J. D.; Thompson, B. C. Preparation of
Semi-Alternating Conjugated Polymers Using Direct Arylation Polymerization (DArP) and
Improvement of Photovoltaic Device Perfomance. J. Polym. Sci. A Polym. Chem. 2017, 55, 3370-
3380. https://doi.org/10.1002/pola.28712.
(2) Livi, F.; Gobalasingham, N. S.; Thompson, B. C.; Bundgaard, E. Analysis of Diverse
Direct Arylation Polymerization (DArP) Conditions toward the Efficient Synthesis of Polymers
Converging with Stille Polymers in Organic Solar Cells. J. Polym. Sci., Part A 2016, 54 (18),
2907–2918. https://doi.org/10.1002/pola.28176.
(3) Qiu, Y.; Worch, J. C.; Fortney, A.; Gayathri, C.; Gil, R. R.; Noonan, K. J. T. Nickel-
Catalyzed Suzuki Polycondensation for Controlled Synthesis of Ester-Functionalized Conjugated
Polymers. Macromolecules 2016, 49 (13), 4757–4762.
https://doi.org/10.1021/acs.macromol.6b01006.
(4) Burkhart, B.; Khlyabich, P. P.; Cakir Canak, T.; LaJoie, T. W.; Thompson, B. C. “Semi-
Random” Multichromophoric Rr-P3HT Analogues for Solar Photon Harvesting. Macromolecules
2011, 44 (6), 1242–1246. https://doi.org/10.1021/ma102747e.

139

Appendix B

Chapter 3: Influence of Directing-Groups on Defect Formation in the Synthesis of
Conjugated Polymers via Direct Arylation Polymerization (DArP) using Sustainable
Solvents
B.1. General
All reactions were performed under dry N2 in oven dried glassware, unless otherwise noted.
Unless otherwise noted, all reagents were purchased and used as received from commercial
sources. Solvents were purchased from VWR and used without purification, unless otherwise
noted. Anhydrous, unstabilized cyclopentyl methyl ether (CPME) was purchased and used as
received. Cs2CO3 was ground into a fine powder and dried at 120 °C in a vacuum oven before use.
5,5’-bis(trimethylstannyl)-2,2’-bithiophene was previously prepared following literature
procedure.
1
All NMR were recorded at 25 °C using CDCl3 on either a Varian Mercury 400 MHz,
Varian VNMRS-500 MHz, or a Varian VNMR-600 MHz. All spectra were referenced to CHCl3
(7.26 ppm), unless otherwise noted. Number average molecular weight (Mn) and polydispersity
(Ð) were determined by size exclusion chromatography (SEC) using a Viscotek GPC Max VE
2001 separation module and a Viscotek Model 2501 UV detector, with 60 °C HPLC grade 1,2-
dichlorobenzene (o-DCB) as eluent at a flow rate of 0.6 mL/min on one 300 × 7.8 mm TSK-Gel
GMHHR-H column (Tosoh Corp). The instrument was calibrated vs. polystyrene standards
(1050−3,800,000 g/mol), and data were analysed using OmniSec 4.6.0 software. Polymer samples
were dissolved in HPLC grade o-dichlorobenzene at a concentration of 0.5 mg ml−1, stirred at 65
°C until dissolved, cooled to room temperature, and filtered through a 0.2 μm PTFE filter.
140

For polymer thin-film measurements, solutions were spin-coated onto pre-cleaned glass
slides from o-dichlorobenzene (o-DCB) solutions at 7 mg/mL. UV−vis absorption spectra were
obtained on a Perkin-Elmer Lambda 950 spectrophotometer. Thicknesses of the samples and
grazing incidence X-ray diffraction (GIXRD) measurements were obtained using Rigaku
diffractometer Ultima IV using a Cu Kα radiation source (λ = 1.54 Å) in the reflectivity and grazing
incidence X-ray diffraction mode, respectively. Crystallite size was estimated using Scherrer’s
equation:
τ = Kλ/(β cosθ) (1)
where τ is the mean size of the ordered domains, K is the dimensionless shape factor (K = 0.9), λ
is the x-ray wavelength, β is the line broadening at half the maximum intensity (FWHM) in radians,
and θ is the Bragg angle.
141

B.2. Monomer Synthesis

Scheme B.1. Monomer Synthesis.

Synthesis of 5-bromothiophene-3-carboxylic acid (2):
To an Erlenmeyer flask equipped with a stir-bar, 3-thiophene carboxylic acid (10 g, 78 mmol, 1
equiv) was dissolved in glacial acetic acid (60 mL). To this, a solution of bromine (5.61 g, 35.1
mmol, 0.9 equiv) in glacial acetic acid (30 mL) was added slowly. The mixture was allowed to stir
for 1 hour and then it was poured in water (300 mL) and stirred for 15 minutes. The solid was
filtered off and washed with water. It was then recrystallized from water (300 mL), filtered, and
dried in under vacuum (~100 mtorr) overnight. 5.83 g, 41%.
1
H-NMR 400 MHz (CDCl3): δ (ppm)
8.11 (d, J = 1.6 Hz, 1H), 7.51 (d, J = 1.6 Hz, 1H). Consistent with literature reports.
2

142

Synthesis of 2-butyloctyl-5-bromothiophene-3-carboxylate (3)
In an oven-dried 3-neck roundbottom flask equipped with a N2 inlet and a stirbar 2 (4.00 g, 19.3
mmol, 1 equiv), DMAP (0.826 g, 23.16 mmol, 0.35 equiv), and DCC (4.78 g, 23.16 mmol, 1.2
equiv), were dissolved in anhydrous DCM (50 mL). This mixture was allowed to stir for 30
minutes. To this, 2-butyloctanol (5.39 g, 28.95 mmol, 1.5 equiv) was added dropwise via syringe.
The mixture was then stirred for 48 hours. The precipitate was filtered off, it was diluted with
water (50 mL), and it was extracted with DCM. The organic extracts were then washed with brine
and dried with Na2SO4. The solvent was stripped and it was purified using column chromatography
(15% DCM/hexanes). 6.30 g, 87%.
1
H-NMR 400 MHz (CDCl3): δ (ppm) 7.97 (d, J = 1.6, 1H),
7.45 (d, J = 1.6 Hz, 1 H), 4.16 (d, J = 5.6 Hz, 2H), 1.74-1.69 (m, 1H), 1.35-1.28 (m, 16H), 0.91-
0.86 (m, 6H). Consistent with literature reports.
3

Synthesis of Bis(2-butyloctyl)[2,2’-bithiophene]-4,4’-dicarboxylate (4):
To a 3-neck round bottom flask equipped with a stir-bar, nitrogen inlet, glass-stopper, Teflon
septum, and condenser was added potassium carbonate ( 9.1 g, 66 mmol, 4 equiv) and
bispinacolatodiboron ( 2.09 g, 8.23 mmol, 0.5 equiv). The flask was evacuated and refilled with
143

N2 3 times. Compound 3 (6.18 g, 16.46 mmol, 1 equiv) and a 50 mL mixture of THF:H 2O (3:1)
was then added, and the mixture was degassed for 20 minutes. Pd(PPh3)2Cl2 ( 693 mg, 0.99 mmol,
0.06 equiv) was quickly added and the mixture degassed for an additional 20 minutes. The Teflon
septum was replaced with a glass stopper, and the mixture was then heated at 80 °C for 24 hours.
The reaction was cooled and extracted with DCM. The extracts were washed with brine, dried with
Na2SO4, and chromatographed using a solvent gradient of 10% DCM/hexanes to 30%
DCM/hexanes to afford a pale yellow, viscous oil (69% yield).
1
H-NMR 400 MHz (CDCl3): δ
(ppm) 7.98 (d, J = 1.2 Hz, 2H), 7.57 (d, J = 1.2 Hz, 2H), 4.19 (d, J = 6.0 Hz, 4H), 1.77-1.73 (m,
2H), 1.39-1.27 (m, 32H), 0.93-0.86 (m, 12H). Consistent with literature reports.
3

Synthesis of Bis(2-butyloctyl)[2,2’-bithiophene]-4,4’-dicarboxylate (5):
To a scintillation vial equipped with a screw cap and stir bar was added 4 ( 267 mg, 0.45 mmol, 1
equiv.), CHCl3 (2 mL), and trifluoroactetic acid (0.5 mL). The vial was wrapped with foil to shield
it from light, and NBS (160.2 mg, 0.9 mmol, 2 equiv.) was added portion wise and it was allowed
to stir for 16 hours. In order to reach completion, an additional 16 mg, 0.2 equiv, of NBS and 1.5
mL of TFA were added and it was allowed to stir for an additional 4 hours. The reaction mixture
was then diluted with water (10 mL) and extracted with CHCl3. The organic extracts were then
144

washed with brine and dried with Na2SO4. Purification was performed using column
chromatography (20% DCM/hexanes). 197 mg, 59%.
1
H-NMR 500 MHz (CDCl3): δ (ppm) 7.35
(s, 2H), 4.21 (d, J = 5.5 Hz, 4H), 1.75-1.73 (m, 2H), 1.41-1.27 (m, 32H), 0.91-0.86 (m, 12H).
Consistent with literature reports.
2,3

Synthesis of 5,5’-dibromo-2,2’-bithiophene (7):
To 3-neck roundbottom flask equipped with a N2 inlet and a stirbar 6 (2.0 g, 12.0 mmol, 1 equiv)
was added and dissolved in DMF (50 mL). The mixture was then cooled to 0
°
C and NBS (4.28 g,
24.06 mmol, 2 equiv.) was added in one portion. This was allowed to slowly warm-up to room
temperature with stirring overnight. The mixture was then poured into water (250 mL) and
recrystallized from a mixtures of hexanes/CHCl3. 2.84 g, 73%.
1
H-NMR 400 MHz (CDCl3): δ
(ppm) 6.96 (d, J = 4.0 Hz), 2H), 6.85 (d, J = 4.0 HZ, 2H). Consistent with literature reports.
4

Synthesis of 2,5-dibromothieno[3,2-b]thienothiophene (9):
Thineno[3,2-b]thiophene (500 mg, 3.57 mmol, 1 equiv) was added to a 3-neck round bottom flask
equipped with a stir-bar, which was then vacuum-backfilled with N2 three times. DMF (7 mL) was
added and the solution was degassed for 15 minutes. It was then cooled to 0
°
C and NBS (1.27 g,
7.13 mmol, 2 equiv.) was added in one portion. The mixture was then stirred for 3 hours, allowing
it to warm to room temperature. Water was added (15 mL) and a precipitate formed that was then
filtered, washed with water, and dried under high-vacuum. The crude product was then
145

recrystallized using a mixture of EtOH/CHCl3. 460 mg, 43%.
1
H-NMR 400 MHz (CDCl3): δ (ppm)
7.17 (s, 2H). Consistent with literature reports.
5

Synthesis of 2,2’-bithiazole (11):
To an oven-dried 3-neck round-bottom flask cooled under N2 was added Bu4NBr. The flask was
then vacuum-backfilled three times with N2. 2-bromothiazole (2.60 g, 16 mmol, 1 equiv), Et(i-
Pr)2N (2.07 g, 16 mmol, 1 equiv.), and toluene (6 mL) were added to the flask. It was then degassed
with N2 for 30 minutes. Pd(OAc)2 (359 mg, 1.6 mmol, 0.1 equiv.) was quickly added and the flask
was heated at 105 °C overnight. The reaction mixture was cooled, H2O (25 mL) was added, and it
was extracted with CHCl3. The combined organics were washed with brine and dried with Na2SO4.
Purification was performed using column chromtagoraphy (20% EtOAc/hexanes). 587 mg, 43%.
1
H-NMR 400 MHz (CDCl3): δ (ppm) 7.90 (d, J = 3.2 Hz, 2H), 7.44 (d, J = 3.2 Hz, 2H). Consistent
with literature reports.
6

Synthesis of 5,5’-dibromo-2,2’-dithiazole (12):
To an oven-dried 3-neck round-bottom flask cooled under N2 was added 2,2’-dithiazole (11) (500
mg, 2.97 mmol, 1 equiv.) and anhydrous DMF (15 mL). NBS (2.14 g, 12 mmol, 4 equiv.) was
added in one portion, and the reaction mixture was heated at 60 °C overnight. After cooling to
room temperature, H2O (25 mL) was added and the mixture was stirred for 15 minutes. The
146

precipitate was filtered off, and it was then recrystallized with MeOH/CHCl 3. 571 mg, 59%.
1
H-
NMR 400 MHz (CDCl3): δ (ppm) 7.17 (s, 2H). Consistent with literature reports.
6

147

B.3.
1
H-NMR for Compounds 2-12.

Figure B.1
1
H NMR of compound 2 in CDCl3 at 25 °C and 400 MHz.

148

Figure B.2
1
H NMR of compound 3 in CDCl3 at 25 °C and 400 MHz.
149

Figure B.3
1
H-NMR of Compound 4 in CDCl3 at 25 °C and 400 MHz.
150

Figure B.4
1
H NMR of Compound 5 in CDCl3 at 25 °C and 400 MHz.

151

Figure B.5
1
H-NMR of monomer 7 in CDCl3 at 25 °C and 400 MHz.
152

Figure B.6
1
H-NMR of monomer 9 in CDCl3 at 25 °C and 400 MHz.

153

Figure B.7
1
H-NMR of compound 11 in CDCl3 at 25 °C and 400 MHz.
154

Figure B.8
1
H-NMR of monomer 12 in CDCl3 at 25 °C and 400 MHz.
155

Figure B.9
1
H-NMR of monomer 13 in CDCl3 at 25 °C and 500 MHz.

156

B.4. Polymer NMR

Figure B.10
1
H-NMR of PDCBT (Stille) collected in CDCl3 at 25 °C and 500 MHz.
157

Figure B.11
1
H-NMR of PDCBT prepared via DArP (entry 3 of Table 2.1). Collected in CDCl3
at 25 °C and 500 MHz.
158

Figure B.12
1
H-NMR of PDCTT (entry 6 of Table 2.1) collected in CDCl3 at 25 °C and 500
MHz. (*)Denotes potential end-group.

159

Figure B.13
1
H-NMR of PDCBTz (entry 7 of Table 2.1) collected in CDCl3 at 25 C and 600
MHz. (*) Denotes potential end-group.

160

Figure B.14 Expanded view of the region δ(ppm)7.75-7.55 in the
1
H-NMR spectra for PDCBT
prepared by DArP (top) and Stille (bottom). Detailing what are likely penultimate protons for the
respective DArP and Stille polymers.

161

B.5. Polymer GIXRD
Table B.1 Polymer GIXRD data.
Polymer 2θ
(degrees)
d100 (Å) Height FWHM
(degrees)
Crystallite size
(nm)
PDCBT- Stille 4.250 20.7729 12801 0.531 14.96546
PDCBT-DArP 4.151 21.2673 2430 0.593 13.40035
PDCBTz 4.251 20.7714 5016 0.691 11.50024

B.6. GPC Traces

Figure B.15 GPC traces for the synthesized polymers.

162

B.7. References
(1) Choi, J.; Kim, K.-H.; Yu, H.; Lee, C.; Kang, H.; Song, I.; Kim, Y.; Oh, J. H.; Kim, B. J.
Importance of Electron Transport Ability in Naphthalene Diimide-Based Polymer Acceptors
for High-Performance, Additive-Free, All-Polymer Solar Cells. Chem. Mater. 2015, 27,
5230–5237. https://doi.org/10.1021/acs.chemmater.5b01274.
(2) Heuvel, R.; Colberts, F. J. M.; Wienk, M. M.; Janssen, R. A. J. Thermal Behaviour of
Dicarboxylic Ester Bithiophene Polymers Exhibiting a High Open-Circuit Voltage. J. Mater.
Chem. C 2018, 6 (14), 3731–3742. https://doi.org/10.1039/C7TC04322H.
(3) Zhang, M.; Guo, X.; Ma, W.; Ade, H.; Hou, J. A Polythiophene Derivative with Superior
Properties for Practical Application in Polymer Solar Cells. Adv. Mater. 2014, 26 (33), 5880–
5885. https://doi.org/10.1002/adma.201401494.
(4) Reuter, L. G.; Bonn, A. G.; Stückl, A. C.; He, B.; Pati, P. B.; Zade, S. S.; Wenger, O. S.
Charge Delocalization in a Homologous Series of α,Α′-Bis(Dianisylamino)-Substituted
Thiophene Monocations. J. Phys. Chem. A 2012, 116 (27), 7345–7352.
https://doi.org/10.1021/jp303989t.
(5) Yuan, Z.; Xiao, Y.; Yang, Y.; Xiong, T. Soluble Ladder Conjugated Polymer Composed of
Perylenediimides and Thieno[3,2-b]Thiophene (LCPT): A Highly Efficient Synthesis via
Photocyclization with the Sunlight. Macromolecules 2011, 44 (7), 1788–1791.
https://doi.org/10.1021/ma1026252.
(6) Oniwa, K.; Kikuchi, H.; Kanagasekaran, T.; Shimotani, H.; Ikeda, S.; Asao, N.; Yamamoto,
Y.; Tanigaki, K.; Jin, T. Biphenyl End-Capped Bithiazole Co-Oligomers for High
Performance Organic Thin Film Field Effect Transistors. Chem. Commun. 2016, 52 (27),
4926–4929. https://doi.org/10.1039/C6CC01352J.
163

Appendix C
Copper Catalyzed Synthesis of Conjugated Copolymers using Direct Arylation
Polymerization
C.1 General
All reactions were performed under dry N2 in oven dried glassware, unless otherwise noted.
Unless otherwise noted, all reagents were purchased and used as received from commercial
sources through VWR. Solvents were purchased from VWR and used without purification, unless
otherwise noted. Cu(I) iodide (99.999%-Cu) PURATREM was purchased from Strem Chemicals
and used as received. Na2CO3, K2CO3, and Cs2CO3 were ground into a fine powder and dried at
120 °C in a vacuum oven before use. Tetrahydrofuran (THF) was dried over sodium/benzophenone
before distillation. Anhydrous N,N-dimethylacetamide (DMA) and N,N,-dimethylformamide
(DMF) were used. All other solvents, such as N,N-diethylacetamide (DEA) and chlorobenzene
(CB) were dried over CaH2 and distilled onto activated molecular sieves (4 Å) prior to use. All
NMR were recorded at 25 °C using CDCl3 on either a Varian Mercury 400 MHz, Varian VNMRS-
500 MHz, or a Varian VNMR-600 MHz. All spectra were referenced to CHCl3 (7.26 ppm), unless
otherwise noted. Number average molecular weight (Mn) and polydispersity (Ð) were determined
by size exclusion chromatography (SEC) using a Viscotek GPC Max VE 2001 separation module
and a Viscotek Model 2501 UV detector, with 70 °C HPLC grade 1,2-dichlorobenzene (o-DCB)
as eluent at a flow rate of 0.6 mL/min on one 300 × 7.8 mm TSK-Gel GMHHR-H column (Tosoh
Corp). The instrument was calibrated vs. polystyrene standards (1050−3,800,000 g/mol), and data
were analysed using OmniSec 4.6.0 software. Polymer samples were dissolved in HPLC grade o-
dichlorobenzene at a concentration of 0.5 mg ml−1, stirred at 65 °C until dissolved, cooled to room
temperature, and filtered through a 0.2 μm PTFE filter.
164

C.2 Monomer Syntheses

Scheme C.1 General synthesis for TPD monomers.
General procedure for 5-Alkyl-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione Syntheses.
A 250 mL single neck round-bottom flask with a stir-bar was charged with S1 (5 g, 29.04 mmol)
and Ac2O (100 mL). A condenser was attached and the mixture heated to 140
N2. After cooling, the condenser was removed and the excess Ac2O was vacuum distilled off. To
the same flask, the alkylamine (1.5 equiv.) and toluene (120 mL) were added, the condenser
2. The mixture was cooled and
the volatiles stripped via rotary evaporation. SOCl2 (42 g, 356 mmol, 26 mL) was then added to
was added slowly to stirring ice water (200 mL) via pipette and it was then neutralized with
NaHCO3. The solid was filtered off, collected, chromatographed (1:1 DCM/hexanes) and
recrystallized with EtOH to afford a white solid.
5-(2-ethylhexyl)-4H-Thieno[3,4-c]pyrrole-4,6(5H)-dione (S2).
Yield:62%.
1
H NMR 500 MHz (CDCl3): δ (ppm) 7.80 (s 2H), 3.52 (d, J = 7.5 Hz, 2H), 1.83-1.78
(m, 1H), 1.36-1.26 (m, 8H), 0.92-0.87 (m, 6H).
13
C NMR (CDCl3): δ (ppm) 162.9, 136.6, 125.4,
42.4, 38.2, 30.5, 28.5, 23.8, 23.0, 14.1, 10.4. Consistent with reported values.
1

165

5-(2-decyltetradecyl)-4H-Thieno[3,4-c]pyrrole-4,6(5H)-dione (S3).
Yield: 83%.
1
H NMR 500 MHz (CDCl3 -
1.80 (m, 1H), 1.34-1.24 (m, 40H), 0.88 (t, 6H, J = 7.0 Hz).
13
C NMR (CDCl3): δ (ppm) 162.9,
136.6, 125.4, 42.8, 36.9, 31.4, 30.0, 29.7-29.3 (overlap), 26.3, 22.7, 14.1. Consistent with reported
values.
2

5-(2-octylnonyl)-4H-Thieno[3,4-c]pyrrole-4,6(5H)-dione (S4).
Yield: 90%.
1
H NMR 500 MHz (CDCl3 -4.07 (m, 1H), 2.06-2.00 (m,
2H), 1.69-1.62 (m, 2H), 1.27-1.22 (m, 24H), 0.85 (t, 6H, J = 6.0 Hz).
13
C NMR (CDCl3): δ (ppm)
163.0, 136.5, 125.2, 52.73, 32.3, 31.8, 29.4, 29.3, 29.2, 26.7, 22.6, 14.1. Consistent with reported
values.
3

Scheme C.2 Synthesis of 2,5-diiodothiophene.
2,5-Diiodothiophene (S6).
In a round-bottomed flask equipped with a stir-bar NIS (2.2 g, 26.18 mmol) and S5 (1.00 g, 11.9
mmol) were dissolved in AcOH (6 mL) and CHCl3 (8 mL). The flask was shielded from light using
aluminium foil, and the reaction mixture was allowed to stir overnight at room-temperature. H2O
(50 mL) was then added and the micture was extracted with CHCl3 (3x25 mL). The organic layer
was washed with aqueous NaHCO3, brine, and then dried with MgSO4. The crude was sent through
a short silica-plug (CHCl3) and then vacuum distilled to afford a yellow oil that slowly crystallized
into a white solid (850 mg, 21%).
1
H NMR 500 MHz (CDCl3): δ 6.94 (s, 2H)
13
C NMR (CDCl3):
δ (ppm) 138.8. 76.2. Consistent with reported values.
4,5

166

Scheme C.3 General synthesis of diiodofluorenes.
2,7-Diiodofluorene (S8).
To a 3-neck round-bottomed flask equipped with a stir-bar and a condenser was added S6 (3.2 g,
19.25 mmol), H2O (10.4 mL), AcOH (51 mL), and H2SO4 (1.6 mL). It was heated at 95 °C until
S6 dissolved. Then the temperature was reduced to 80 °C and I2 (3.2 g, 12.7 mmol) and H5IO6 (1.4
g, 6.35 mmol) were added. It was stirred at 80 °C until the disappearance of I2 was observed
(approximately 2 hours) and then cooled to room temperature. The reaction mixture was then
poured into water (200 mL), NaHSO3 aq. was added to quench trace I2, and NaHCO3 was added
to quench excess acid. The solid was then filtered off and collected. Recrystallized from
MeOH/CHCl3 to yield an off-white, fibrous solid (2.9 g, 36%).
1
H NMR 400 MHz (CDCl3): δ
(ppm) 7.88 (s, 2H) 7.70 (d, 2H, J = 8.0 Hz), 7.50 (d, 2H, J = 8.0 Hz). Consistent with reported
values.
6

General procedure for 9,9-Bis(alkyl)-2,7-diiodofluorene Syntheses (S9-S10).
To a 3-neck round-bottomed flask under N2 atmosphere with DMSO (8 mL) at 0 °C was added
ground KOH (9.5 mmol, 530 mg), KI (0.19 mmol, 32 mg), S7 (1.6 mmol, 670 mg), and the alkyl
bromide (2.2 equivalents). It was slowly allowed to reach room temperature by stirring overnight.
H2O was then added (10 mL) and the mixture was extracted with hexanes. The organic layers were
then washed with water, brine, and dried with MgSO4. Purification was performed by column
167

chromatography using hexanes as the eluent, and the solid was recrystallized using EtOH to obtain
colorless crystals.
9,9-Bis(hexyl)-2,7-diiodofluorene (S9).
Yield: 29%.
1
H NMR 500 MHz (CDCl3): δ (ppm) 7.66-7.63 (m, 4H), 7.41 (d, 2H, J = 8.0 Hz),
1.90-1.87 (m, 4H), 1.27-1.05 (m, 20H), 0.83 (t, 6H, J = 10 Hz), 0.59-0.56 (m, 4H)
13
C NMR
(CDCl3): δ (ppm) 152.5, 139.8, 136.0, 132.0, 121.5, 93.1, 55.5, 40.1, 31.8, 29.8, 29.2, 29.1, 23.6,
22.6, 14.1. Consistent with reported values.
7

9,9-Bis(octyl)-2,7-diiodofluorene (S10).
Prepared in a similar as S8, but with n-octylbromide in place of n-hexylbromide. Yield: 80%.
1
H
NMR 500 MHz (CDCl3): δ (ppm) 7.66-7.64 (m, 4H), 7.41 (d, 2H, J = 7.5 Hz), 1.91-1.87 (m, 4H),
1.16-1.04 (m, 12H), 0.78 (t, 6H, J = 8.0 Hz), 0.61-0.55 (m, 4H)
13
C NMR (CDCl3): δ (ppm) 152.5,
139.7, 136.0, 132.0, 121.5, 93.1, 55.5, 40.1, 31.4, 29.6, 23.6, 22.6, 14.0. Consistent with reported
values.
8

Scheme C.4 Synthesis of S12.
1,4-bis[(2-ethylhexyloxy)]-benzene (S11).
To a 3-neck 100 mL round bottom flask equipped with a stir-bar, hydroquinone (5.0 g, 45.5 mmol),
KOH (10.21 g, 182 mmol), DMSO (30 mL) were added and stirred at 80 °C for 30 minutes. 2-
Ethylhexyl bromide (19.22 g, 99.5 mmol) was added, and the reaction mixture was stirred
overnight at 80 °C. After cooling down to room temperature, the reaction mixture was poured into
168

100 mL of water, extracted with diethyl ether three times, and the combined organic layers were
washed with 10% NaOH solution three times. The organic layer was dried over anhydrous MgSO4
followed by the removal of diethyl ether via rotary evaporation. The crude product was purified
by column chromatography (hexanes:DCM = 7:3) to afford a colorless oil (9.7g, 63.8%).
1
H NMR
400 MHz (CDCl3): δ (ppm) 7.12 (s, 2H), 3.82 (d, 4H, J = 5.0 Hz), 1.76-1.71 (m 2H), 1.53-1.27
(m, 16H), 0.94-0.89 (m, 12H). Consistent with reported values.
9

1,4-bis[(2-ethylhexyloxy)]-2,5-diiodobenzene (S12).
To a 250 mL round bottom flask equipped with a stir-bar and a condenser, KIO3 (1.50g, 7.02
mmol), 1,4-Bis[(2-ethylhexyl)oxy]benzene (5.89 g, 17.38 mmol), AcOH (100 mL) were added,
followed by dropwise addition of H2SO4 (2 mL), H2O (4 mL). I2 (5.33g, 20.98 mmol) was added
portion-wise over a period of 30 minutes, and the reaction mixture was allowed to reflux at 130
°C for 24 hours. After cooling down to room temperature, the reaction mixture was poured into
200 mL of water, quenched with NaHSO3 to remove I2, quenched with NaHCO3 to remove excess
acid, and extracted with diethyl ether three times. The combined organic layer was washed with
saturated NaHCO3 solution three times, dried over anhydrous MgSO4, and concentrated under
pressure. The crude product was purified by column chromatography (hexanes) to afford a
colorless viscous oil (2.6g, 26.1%).
1
H NMR 500 MHz (CDCl3): δ (ppm) 7.16 (s, 2H), 3.81 (d, J
= 5.0 Hz), 1.76- 1.69 (m, 2H), 1.57-1.50 (m, 6H), 1.45-1.40 (m, 2H), 1.34-1.33 (m, 8), 0.95-0.90
(m, 12H).
13
C NMR (CDCl3): δ (ppm) 152.9, 122.4, 86.0, 72.4, 39.5, 30.5, 29.0, 23.9, 23.0, 14.1,
11.2. Consistent with reported values.
9

169

C.3. Polymer Syntheses
General procedure for polymerizations.
An oven-dried 15 mL high-pressure vessel equipped with a stir-bar was stoppered with a rubber-
septum and cooled under a flow N2. The aryl dihalide (0.125 mmol, 1 equiv.), the TPD acceptor
(0.125 mmol, 1 equiv.), K2CO3 (40 equiv.), and phenanthroline (0.5 equiv) were added. The vessel
was further sparged with N2 (3 min.). Then N,N-dimethylacetamide (2.5 mL) was added and the
mixture was degassed with N2 for 15 min. CuI (0.5 equiv) was quickly added and the vessel sealed
with a Teflon screw-cap. The vessel was then submerged in a pre-heated oil bath (140 °C) for 72
hours. The reaction was then cooled, and the mixture was precipitated into cold 10%
NH4OH/methanol solution, using CHCl3 to dissolve any solids. The precipitate was then collected
via filtration, and it was washed with water, methanol, acetone, and hexanes until the wash
appeared colorless. It was then dried under high-vacuum overnight.

170

Table C.1 Synthesis and optimization of P1 using Cu-catalyzed DArP.
a

phenanthroline (phen), 4,4’-dimethyl-2,2’-bipyridine (dmby)1,1’-bisferrocenediyl-
bis(diphenylphosphine (dppf), neocuproine (neocup).
b
99.999%-Puratrem Cu(I) iodide was used
as the copper source with a 1:1 ratio to the ligand; .
c
N,N-dimethylacetamide (DMA), N-
methylpyrrolidone (NMP), N,N-diethylacetamide (DEA), and chlorobenzene (CB); solvent
mixtures were 3:1 cosolvent:DMF.
d
Determined for polymer products after purification; no
reaction (NR), no polymer (NP).
Initially, our investigation for optimal conditions for the synthesis of P1 looked at the
optimal base (entries 1-5), with only K2CO3 providing a reaction (qualitatively) but no isolable
Entry Ligand
a
Cat.
Mol
b
%
Solvent

Temp.
(°C)
Tim
e (h)
Base Mn
(kDa)
d
, ᴆ
Yield
d

(%)
1 phen 5 DMF/CB 140 72 Cs2CO3 NR NR
2 phen 20 DMF /CB 140 72 Na2CO3 NR NR
3 phen 20 DMF/CB 140 72 t-BuOLi NP NP
3 phen 20 DMF/CB 140 72 K3PO4 NR NR
5 phen 20 DMF/CB 140 72 K2CO3 NP NP
6 phen 10 THF 120 72 K2CO3 1.1; 1.61 34
7 phen 10 DMF 140 72 K2CO3 1.5, 1.77 46
8 phen 50 DMA 140 72 K2CO3 5.6, 2.20 23
9 phen 50 DMA 166 72 K2CO3 4.2, 2.85 29
10 phen 50 NMP 140 72 K2CO3 NR NR
11 phen 50 DEA 140 72 K2CO3 5.4, 1,56 37
12 dppf 50 DMA 140 72 K2CO3 NR NR
13 dmby 50 DMA 140 72 K2CO3 2.6, 1.68 24
14 neocup 50 DMA 140 72 K2CO3 NR NR
15 phen 5 DMA 140 88 K2CO3 2.9, 1.62 15
16 phen 25 DMA 140 88 K2CO3 3.7, 2.13 49
17 phen 50 DMA 140 48 40 eq
K2CO3
8.2, 1.64 14
171

polymer product. While t-BuOLi did provide a reaction, it was only the rapid decomposition of
the monomers. At this point, we were unaware of the significance of the amide solvent and were
using solvent mixtures with chlorobenzene in hopes to keep any polymer product in solution. We
had observed that aryliodides only reacted, and so we were certain chlorobenzene would remain
inert. Also, chlorobenzene has been proven successful in Pd-based DArP.
10
Next, through
optimization of the solvent, we discovered the importance of the amide solvent (entries 6-8) with
DMA providing the best Mn (5.6 kDa) along with an increase in catalyst loading (50 mol %). The
importance of this solvent is further discussed in regards to Figure C.26, below. We then looked
at higher temp (entry 9) and other amide solvents, such as NMP and DEA (entries 10 and 11,
respectively), but the original conditions for DMA (entry 8) were still the best observed. From
screening bidentate ligands (entries 12-14), only dmby (entry 13) provided polymer product albeit
with lower Mn compared to phenanthroline (2.6 versus 5.6 kDa, respectively). Lowering the
catalyst loading to 5 mol% (entry 15) and 25 mol% (entry 16), provided satisfactory M n but less
than that of 50 mol % (2.9 and 3.7 kDa versus 5.6 kDa). We believe the lower concentration of
our conditions (0.1 M) relative to Daugulis’ initial study (1 M) is a major influence in determining
the need for a higher catalyst loading. Attempts to replicate Daugulis’ conditions exactly, in
regards to solvent (DMF), concentration (1 M), and catalyst loading (10 mol %), did not afford
any polymer product, although a reaction was observed indicating the formation of very low M n
oligomers. This is likely due to the premature precipitation of the product, consequential of the
low solubility in the amide solvents studied and the high concentration (1 M). Lastly, we looked
at increasing the equivalents of base and found this provided the highest value for Mn (8.1 kDa).

172

poly[(2,5- phenylene])-alt-(5-(2-ethylhexyl)-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione)] (P1).
Yellow/orange solid.
1
H NMR 600 MHz (CDCl3): δ (ppm) 8.30-7.80 (b, 4H), 3.79-3.54 (b, 2H),
2.10-1.80 (b, 1H), 1.70-1.0 (b, 40H), 0.86 (b, 6H).

poly[(5-(2-ethylhexyl)-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione-1,3-diyl)-alt-(9,9-
dihexylfluorene-2,7-diyl)] (P2).
Dark purple solid.
1
H NMR 600 MHz (CDCl3): δ (ppm) 8.03 (b, 2H), 3.56 (b, 2H), 1.91 (b, 1H),
1.25 (b, 40 H), 0.86 (b, 6H).
11

173

poly[(2,5-bis[(2-ethylhexyl)oxyphenylene])-alt-(5-(2-ethylhexyl)-4H-thieno[3,4-c]pyrrole-
4,6(5H)-dione)] (P3).
Bright orange solid collected in hexanes fraction.
1
H NMR 600 MHz (CDCl3): δ (ppm) 8.33 (b,
2H),4.18 (b, 4H), 3.59 (b, 2H), 1.94-1.85 (b, 3H), 1.57-1.15 (b, 24H), 0.94-0.83 (b, 18H).
12

poly[(5-(2-ethylhexyl)-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione-1,3-diyl)-alt-(9,9-
dihexylfluorene02,7-diyl)] (P4).
Yellow solid.
1
H NMR 600 MHz (CDCl3): δ (ppm) 8.27-8.23 (m, 4 H), 7.86 (d, 2H, J = 7.8 Hz),
3.65 (b, 2H), 2.17 (b, 4H), 1.92 (b, 1H), 1.54-1.34 (b, 8H), 1.14 (b, 12H), 0.98-0.93 (b, 6H), 0.78
(b, 10H).
13,14

174

poly[(5-(2-ethylhexyl)-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione-1,3-diyl)-alt-(9,9-
dihexylfluorene02,7-diyl)] (P5).
Yellow solid.
1
H NMR 600 MHz (CDCl3): δ (ppm) 8.28-8.21 (b, 4H), 7.786 (b, 2H), 3.62 (b, 2H),
2.16 (b, 4H), 1.97 (b, 1H), 1.41-1.10 (b, 52H), 0.87 (b, 6H), 0.79-0.69 (b, 10H).
13,14

poly[(5-(2-ethylhexyl)-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione-1,3-diyl)-alt-(9,9-dioctylfluorene-
2,7-diyl)] (P6).
Yellow solid.
1
H NMR 600 MHz (CDCl3): δ (ppm) 8.26-8.24 (m, 4H), 7.86 (d, 2H, J = 7.8 Hz),
3.65 (b, 2H), 2.17 (b, 4H), 1.93 (b, 1H), 1.56-1.34 (b, 8H), 1.20-1.12 (b, 20H), 0.98-0.92 (b, 6H),
0.82-0.68 (b, 10H).
13,14

175

poly[(5-(2-ethylhexyl)-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione-1,3-diyl)-alt-(9,9-dioctylfluorene-
2,7-diyl)] (P7).
Yellow solid.
1
H NMR 600 MHz (CDCl3): δ (ppm) 8.30 (d, 2H, J = 7.2 Hz), 8.16-8.14 (b, 2 H),
7.86 (d, 2H, J = 7.8 Hz), 4.26 (b, 1H), 2.15 (b, 6H), 1.76 (b, 2H), 1.33-1.13 (b, 44H), 0.87-0.80 (b,
16H).
13,14

176

C.4 Monomer NMR

Figure C.1
1
H NMR of S2 in CDCl3 at 25 °C.

177

Figure C.2
13
C NMR of S2 in CDCl3 at 25 °C.
178

Figure C.3
1
H NMR of S3 in CDCl3 at 25 °C.
179

Figure C.4
13
C NMR of S3 in CDCl3 at 25 °C.
180

Figure C.5
1
H NMR of S4 in CDCl3 at 25 °C.
181

Figure C.6
13
C NMR of S4 in CDCl3 at 25 °C.
182

Figure C.7
1
H NMR of S6 in CDCl3 at 25 °C.
183

Figure C.8
13
C NMR of S6 in CDCl3 at 25 °C.
184

Figure C.9
1
H NMR of S8 in CDCl3 at 25 °C.
185

Figure C.10
13
C NMR of S8 in CDCl3 at 25 °C.
186

Figure C.11
1
H NMR of S9 in CDCl3 at 25 °C.
187

Figure C.12
13
C NMR of S9 in CDCl3 at 25 °C.
188

Figure C.13
1
H NMR of S10 in CDCl3 at 25 °C.
189

Figure C.14
13
C NMR of S10 in CDCl3 at 25 °C.
190

Figure C.15
1
H NMR of S11 in CDCl3 at 25 °C.
191

Figure C.16
1
H NMR of S12 in CDCl3 at 25 °C.
192

Figure C.17
13
C NMR of S12 in CDCl3 at 25 °C.
193

C.5 Polymer NMR

Figure C.18
1
H NMR (600 MHz) of P1 in CDCl3 at 25 °C. End groups denoted with *. Entry 8
of Table 3.1.
194

Figure C.19
1
H NMR (600 MHz) of P2 in CDCl3 at 25 °C. End groups denoted with *. Sample
for P2 was 2.38 kDa synthesized using DMF since higher Mn samples were only soluble in hot
CHCl3 and DCB.
195

Figure C.20
1
H NMR (600 MHz) of P3 in CDCl3 at 25 °C. End groups denoted with *. Entry P3
of Table 3.2.
196

Figure C.21
1
H NMR (600 MHz) of P4 in CDCl3 at 25 °C. End groups denoted with *. Entry P4
of Table 3.2.
197

Figure C.22
1
H NMR (600 MHz) of P5 in CDCl3 at 25 °C. End groups denoted with *. Entry
P5a of Table 3.2.
198

Figure C.23
1
H NMR (600 MHz) of P6 in CDCl3 at 25 °C. End groups denoted with *. Entry
P6a of Table 3.2.
199

Figure C.24
1
H NMR (600 MHz) of P7 in CDCl3 at 25 °C. End groups denoted with *. Entry P7
of Table 3.2.

200

C.6 Proposed Catalytic Cycles for Cu-DArP

Figure C.25 Proposed catalytic cycles (a) and (b) for the Cu-catalyzed DArP where the bidentate
ligand is phenanthroline. TPD is simplified as a thiophene (IIa) for clarity.
Based on the results from the optimization of polymerization conditions for P1 and the
polymerization outcomes for the polymers listed in Table 3.2, some insight regarding potential
mechanisms can be gained. The proposed mechanisms, shown in Figure C.25a and S1b, are based
on the experimental findings reported here and previous work regarding Cu-catalyzed
201

arylations.
15–19
However, continuing work to support either pathway is still ongoing. Specifically,
it was found that solvent, base, and monomer sterics were critical factors for the polymerization.
The effect of solvent and base may be due to their participation in a concerted-metallation-
deprotonation (CMD) step (II), shown in Figure C.25a, and where the solvent potentially
participates as a stabilizing ligand throughout the catalytic cycle (I and IIIa). The transition state
for the CMD step and the oxidative addition step to form IV would require displacement of the
amide solvent, and this could largely be inhibited through steric interactions from coordinating or
approaching monomers due to the alkyl substituents. Conversely, it is possible the carbonyl of the
TPD functions as a directing-group affording IIb and IIIb (Figure C.25b). In regards to both of
the proposed catalytic cycles, it is plausible that an equilibrium exists between the species IIIa and
IIIb before the formation of IV .

202

C.7 References
(1) Piliego, C.; Holcombe, T. W.; Douglas, J. D.; Woo, C. H.; Beaujuge, P. M.; Frechet, J. M.
J. Synthetic Control of Structural Order in N-Alkylthieno[3,4-c]Pyrrole-4,6-Dione-Based
Polymers for Efficient Solar Cells. J. Am. Chem. Soc. 2010, 132, 7595–7597.
https://doi.org/10.1021/ja103275u.
(2) Qing, W.; Liu, Z.; Yang, S.; Tan, L.; Yang, Y.; Zhang, D.; Li, J. Modulating Carrier
Transfer Ability-Linker Effect on Thieno[3,4-c]Pyrrole-4,6-Dione Based Conjugated Polymers.
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206

Appendix D
Sustainable Synthesis of a Fluorinated Arylene Conjugated Polymer via Cu-Catalyzed
Direct Arylation Polymerization (DArP)
D.1 General
All reactions were performed under dry N2 in oven dried glassware, unless otherwise noted.
Unless otherwise noted, all reagents were purchased and used as received from commercial
sources through VWR. Solvents were purchased from VWR and used without purification, unless
otherwise noted. Cu(I) iodide (99.999%-Cu) PURATREM was purchased from Strem Chemicals
and used as received. 2,2',3,3',5,5',6,6'-Octafluorobiphenyl was purchased from TCI and used as
received. 9,9-bis(octyl)-2,7-diiodofluorene monomer was prepared previously following reported
procedures.
1
K3PO4 was ground into a fine powder and dried at 120 °C in a vacuum oven before
use. Anhydrous N,N-dimethylacetamide (DMA) was purchased from Alfa Aeser and used as
received. All
1
H NMR were recorded at 25 °C using CDCl3 on either a Varian Mercury 400 MHz,
Varian VNMRS-500 MHz, or a Varian VNMR-600 MHz. All spectra were referenced to CHCl3
(7.26 ppm), unless otherwise noted.
19
F NMR were collected in CDCl3 at 25 °C and externally
referenced to hexafluorobenzene (-162.9 ppm). Number average molecular weight (Mn) and
polydispersity (Ð) were determined by size exclusion chromatography (SEC) using a Viscotek
GPC Max VE 2001 separation module and a Viscotek Model 2501 UV detector, with 70 °C HPLC
grade 1,2-dichlorobenzene (o-DCB) as eluent at a flow rate of 0.6 mL/min on one 300 × 7.8 mm
TSK-Gel GMHHR-H column (Tosoh Corp). The instrument was calibrated vs. polystyrene
standards (1050−3,800,000 g/mol), and data were analysed using OmniSec 4.6.0 software.
Polymer samples were dissolved in HPLC grade o-dichlorobenzene at a concentration of 0.5 mg
207

ml
−1
, stirred at 110-120 °C until dissolved, cooled to room temperature, and filtered through a 0.2
μm PTFE filter.
D.2 An Example of a Polymerization (Entry 10 of Table 5.1)
An oven-dried 15 mL high-pressure vessel equipped with a stir-bar was stoppered with a rubber-
septum and cooled under a flow N2. The 9,9-bis(octyl)-2,7-diiodofluorene (0.125 mmol, 1 equiv.),
2,2',3,3',5,5',6,6'-Octafluorobiphenyl (0.125 mmol, 1 equiv.), K3PO4 (4 equiv.), and
phenanthroline (0.15 equiv) were added. The vessel was further sparged with N2 (3 min.). Then
N,N-dimethylacetamide (0.5 mL) was added and the mixture was degassed with N 2 for 10 min.
CuI (0.15 equiv) was quickly added and the vessel sealed with a Teflon screw-cap. The vessel was
then stirred at room temperature for 5 minutes. It was then submerged in a pre-heated oil bath with
moderate stirring for 16 hours. The reaction was then cooled to room temperature, solids were
dissolved in hot dichlorobenzene (3-5 mL), and the mixture was precipitated into a cold 10% (v:v)
NH4OH/methanol solution with high-stirring (125 mL). The white precipitate was then collected
via filtration, and it was washed with water, methanol, acetone, and hexanes several times yielding
a brown/tan solid. The polymer was collected and dissolved in hot 1,2-dichlorobenzene (3-5 mL),
precipitated into cold MeOH (100 mL), and filtered to yield an off-white/grey solid. It was then
dried under high-vacuum overnight.
poly[(9,9-dioctylfluorene-2,7-diyl)-(2,2′,3,3′,5,5′,6,6′-octafluoro-4,4′-diphenylene)] (PDOF-OD).
1
H NMR 500 MHz (CDCl3): δ (ppm) 7.94 (br, 2H), 7.59 (br, 4H), 2.06 (br, 4H), 1.15 (br, 20H),
0.83 (br, 10H).
19
F NMR 470 MHz (CDCl3): δ (ppm) -135.0 (s), -138.9 (s).

208

D.3 NMR of Synthesized Monomer

Figure D.1
1
H NMR of 9,9-bis(octyl)-2,7-diiodofluorene. Collected in CDCl3 at 25 °C and 500
MHz. Referenced to previous reports.
1

209

D.4 Polymer NMR

Figure D.2
1
H NMR of PDOF-OD synthesized using the conditions outlined in Table 5.1 (Entry
3). Collected in CDCl3 at 25 °C and 500 MHz. Referenced to previous reports.
2

210

Figure D.3
1
H NMR of PDOF-OD synthesized using the conditions outlined in Table 5.1 (Entry
10). Collected in CDCl3 at 25 °C and 500 MHz. Referenced to previous reports.
2

211

Figure D.4
1
H NMR of PDOF-OD synthesized using the conditions outlined in Table 5.1 (Entry
12). Collected in CDCl3 at 25 °C and 500 MHz. Referenced to previous reports.
2,3

212

Figure D.5
19
F NMR of PDOF-OD synthesized using the conditions outlined in Table 5.1 (Entry
3). Collected in CDCl3 at 25 °C and 470 MHz. Referenced to previous reports.
2,3

213

Figure D.6
19
F NMR of PDOF-OD synthesized using the conditions outlined in Table 5.1 (Entry
10). Collected in CDCl3 at 25 °C and 470 MHz. Referenced to previous reports.
2,3

214

D.5 GPC Traces of PDOF-OD Polymers

Figure D.7 GPC traces of PDOF-OD polymers.

215

D.6 Proposed End-Group Assignments

Figure D.8 Proposed end-group assignments based on the model compounds S1
4
, S2
4
, S3
5
, and
S4
6
. The spectra for which all were collected in CDCl3. Colors of lettering (a-d and A-C’)
correlate to the assigned proton (Ha-Hd) on the model compound, the protons of PDOF-OD (A-
C’), and the corresponding resonances for the
1
H NMR spectrum depicted above. The
1
H NMR
spectrum is that of Entry 3 (Table 5.1), and was collected in CDCl3 at 500 MHz and 25 °C.
In order to elucidate the identity of the end-groups observed in the
1
H NMR spectra for
PDOF-OD, a series of model compounds were studied (S1-S4) where the resonances were
explicitly assigned or inferred based on pronounced trends between the compounds. Based on the
trends and assignments of the resonances for the protons of the model compounds, the end-groups
were assigned for PDOF-OD. While the model compounds S2-S4 contain the tetrafluorobenzene
unit and S1 contains the pentafluorobenzene unit, correlations and assignments can still be made
with reasonable certainty since the chemical shifts for PDOF-OD and PDOF-TP do not contain
appreciable differences regarding chemical shift or the types of resonances observed.
2,5,7,8
This is
likely due to the aryl-substituent of the fluorene being orthogonal or close to orthogonal with the
fluorene, limiting the extent of orbital and electronic overlap between them. The c,c’ end-groups
216

for PDOF-OD (Figure D.8) were assigned to the doublet centered at 7.83 ppm (J = 8.0 Hz) based
on the observed resonances for Hc with model compounds S1-S4, where that same proton is shown
in the range of 7.85-7.77 ppm as a doublet with J = 7.2-7.9 Hz.
The next set of end-groups for PDOF-OD, d, b, and b’ (7.72-7.70 ppm), are based off
several observations with the model compounds and the spectra obtained for PDOF-OD. S4
contains a 1H multiplet at 7.80-7.74 ppm that was assigned as Hd, since it is not observed with any
of the other model compounds (S1-S3), which all possess various substituents in that position,
such as an aryl group (S1 and S3) or a bromine (S2). This gives reasonable evidence for the
resonance in the PDOF-OD spectrum at 7.72-7.70 ppm to be assigned as containing Hd, since it is
in close-range with regards to chemical shift. It is believed that the b and b’ resonances are
overlapping that of Hd, since a doublet is apparent and the calculated coupling-constant (J) is 8.0
Hz, which matches with that of the coupling-constant calculated for c and c’. Although the
resonances for Hb for the model compounds are in the range of 7.47-7.40 ppm, it is possible that
the adjacent octafluorobiphenyl has an enhanced deshielding effect relative to tetrafluorobenzene
with regards to the end-group protons. The idea that the doublet assigned for the b, b’ end-group
can be assigned to the penultimate c, c’ resonances was discounted, since those would be expected
to be observed farther downfield based on the values for Hc in S3 (7.85 ppm). Further evidence
that the d, b, and b’ resonances are overlapping is provided with the relative values for the
integrations of the c, c’ and d, b, b’ resonances, which are 2.00 and 3.04, respectively, or a 1:1.50
integral ratio. The idea that this resonance could be an overlap between c (excluding c’) and d was
also discounted, since the integral ratio between these resonances would be 1:2.
The end-groups a,a’ for PDOF-OD (7.53-7.50 ppm) were assigned based on the chemical-
shift values assigned to Ha in the model compounds (S1-S4), which are in the range of 7.53-7.46
217

ppm. Determining an accurate value for the integration of these resonances to compare to that of
c,c’ and d, b, b’ was not possible due to the significant overlap of this resonance with that of A-A’
and B-B’ for PDOF-OD. It should be noted that end-groups for a halogenated fluorene were not
assigned, since resonances based off of model compound S2 in the range of 7.51-7.40 were not
observed. This is likely do to dehalogenation, which is observed and reported in various DArP
methodologies.
1,9,10
We also postulate that the minor resonance at 7.38 ppm is attributable to Hf,
or the proton of the octafluorobiphenyl end-group. However, this is further downfield and than the
reported values for tetrafluorobenzene (7.13-7.02), and other corresponding resonances are not
observed although this may be due to overlap. We hypothesize that octafluorobenzene may have
a more pronounced deshielding effect than octafluorobenzene, leading to the appearance of this
resonance at 7.38 ppm. This is further supported with a study detailing that the protons of
perfluorinated phenylene compounds, such as octofluorobenzene, have chemical shifts in the range
of 7.35-7.27 ppm.
11

218

D.7 References
(1) Pankow, R. M.; Ye, L.; Thompson, B. C. Copper Catalyzed Synthesis of Conjugated
Copolymers Using Direct Arylation Polymerization. Polym. Chem. 2018, 9 (30), 4120–4124.
https://doi.org/10.1039/C8PY00913A.
(2) Lu, W.; Kuwabara, J.; Iijima, T.; Higashimura, H.; Hayashi, H.; Kanbara, T. Synthesis of
π-Conjugated Polymers Containing Fluorinated Arylene Units via Direct Arylation: Efficient
Synthetic Method of Materials for OLEDs. Macromolecules 2012, 45 (10), 4128–4133.
https://doi.org/10.1021/ma3004899.
(3) Saito, H.; Kuwabara, J.; Kanbara, T. Facile Synthesis of Fluorene-Based π-Conjugated
Polymers via Sequential Bromination/Direct Arylation Polycondensation. J. Polym. Sci. Part A:
Polym. Chem. 2015, 53 (19), 2198–2201. https://doi.org/10.1002/pola.27689.
(4) Wakioka, M.; Kitano, Y.; Ozawa, F. A Highly Efficient Catalytic System for
Polycondensation of 2,7-Dibromo-9,9-Dioctylfluorene and 1,2,4,5-Tetrafluorobenzene via Direct
Arylation. Macromolecules 2013, 46 (2), 370–374. https://doi.org/10.1021/ma302558z.
(5) Lu, W.; Kuwabara, J.; Kanbara, T. Polycondensation of Dibromofluorene Analogues with
Tetrafluorobenzene via Direct Arylation. Macromolecules 2011, 44 (6), 1252–1255.
https://doi.org/10.1021/ma1028517.
(6) Luo, Z.-J.; Zhao, H.-Y.; Zhang, X. Highly Selective Pd-Catalyzed Direct C–F Bond
Arylation of Polyfluoroarenes. Org. Lett. 2018, 20 (9), 2543–2546.
https://doi.org/10.1021/acs.orglett.8b00692.
219

(7) Hayashi, S.; Koizumi, T. Chloride-Promoted Pd-Catalyzed Direct C–H Arylation for
Highly Efficient Phosphine-Free Synthesis of π-Conjugated Polymers. Polym. Chem. 2015, 6 (28),
5036–5039. https://doi.org/10.1039/C5PY00871A.
(8) Hayashi, S.; Togawa, Y.; Kojima, Y.; Koizumi, T. Direct Arylation of Fluoroarenes toward
Linear, Bent-Shaped and Branched π-Conjugated Polymers: Polycondensation Post-
Polymerization Approaches. Polym. Chem. 2016, 7 (36), 5671–5686.
https://doi.org/10.1039/C6PY01237J.
(9) Grenier, F.; Goudreau, K.; Leclerc, M. Robust Direct (Hetero)Arylation Polymerization in
Biphasic Conditions. J. Am. Chem. Soc. 2017, 139 (7), 2816–2824.
https://doi.org/10.1021/jacs.6b12955.
(10) Pankow, R. M.; Gobalasingham, N. S.; Munteanu, J. D.; Thompson, B. C. Preparation of
Semi-Alternating Conjugated Polymers Using Direct Arylation Polymerization (DArP) and
Improvement of Photovoltaic Device Perfomance. J. Polym. Sci. A Polym. Chem. 2017, 55, 3370-
3380. https://doi.org/10.1002/pola.28712.
(11) Heidenhain, S. B.; Sakamoto, Y.; Suzuki, T.; Miura, A.; Fujikawa, H.; Mori, T.; Tokito,
S.; Taga, Y. Perfluorinated Oligo(p-Phenylene)s: Efficient n-Type Semiconductors for Organic
Light-Emitting Diodes. J. Am. Chem. Soc. 2000, 122 (41), 10240–10241.
https://doi.org/10.1021/ja002309o.

Abstract (if available)

Abstract Conjugated polymers are ubiquitous materials in organic electronic applications, including organic photovoltaics (OPV), organic field-effect transistors (OFET), light-emitting diodes (OLED), and bioelectronic devices. The pursuit and study of conjugated polymers is largely due to the lower-cost of synthesis, ease of device fabrication, and broader scope of applications these materials can potentially provide in comparison to their inorganic counterparts. This presents a class of materials that can address the environmental concerns associated with the production of alternative energy and consumer electronic devices. Specifically, certain conjugated polymers can be synthesized using low-cost commercial reagents at large-scale, can be solution processed allowing for roll-to-roll device fabrication, and possess desirable mechanical properties, such as flexibility and stretchability. However, the synthesis of conjugated polymers often proceeds via transition-metal catalysed cross-coupling reactions, which invoke the use of a transmetallating reagent, e.g. Migita-Stille or Suzuki-Miyuara polymerizations. These methods for polymerization, while highly efficient, require a greater number of synthetic steps and toxic, highly hazardous reagents for the instillation of the transmetallating reagent on the monomer. Such synthetic pathways counter the ideologies of sustainability and the minimization of environmental impact conjugated polymers seek to address. In contrast, direct arylation polymerization (DArP) provides conjugated polymers via C-H activation, allowing for a streamlined synthetic pathway void of additional synthetic steps, toxic and hazardous reagents, and the generation of large amounts of waste. Despite this, DArP still possess inherent issues regarding sustainability, such as the reaction solvent and the transition metal catalyst. In this dissertation, strategies for improving the sustainability of DArP are provided through the development of polymerization conditions that replace hazardous, unsustainable solvents with relatively non-toxic, sustainable alternatives, and conditions are developed that use more earth-abundant transition metal catalysts. ❧ In Chapter 1, an overview of sustainable conditions for DArP is detailed. This includes describing the synthesis of various conjugated polymers using sustainable solvents with palladium catalysts and the synthesis of conjugated polymers with more earth abundant transition metals, such as copper. Additionally, methods such as oxidative direct arylation polymerization (Oxi-DArP) and Cu-catalyzed Oxi-DArP are presented, which proceed without any pre-functionalization of the monomer using a C-H/C-H dehydrogenative coupling pathway. This chapter summarizes and provides the background for the work detailed in Chapters 2-5. ❧ In Chapter 2, a broad scope study of sustainable solvents is provided, including those derived from biomass. These solvents are applied towards the synthesis of the conjugated polymer PPDTBT, which has been shown to provide desirable properties, in applications such as OPV devices, and possess a streamlined and straightforward monomer synthesis. From the broad scope study, we identify a solvent, cylcopentyl methyl ether (CPME), that allows for the synthesis of PPDTBT in good yields and with high molecular weight (Mₙ). To further explore the utility of the solvent in a general setting, conditions with CPME are developed for the synthesis of P3HT, which is a conjugated polymer found in various organic electronic applications. Each of the polymers is fully structural characterized, and it is found that CPME allows for the defect-free synthesis of PPDTBT and P3HT. ❧ In Chapter 3, conditions that use CPME as a solvent are developed for the synthesis of the conjugate polymer PDCBT. This polymer has garnered recent attention because of its relative ease of synthesis, structural tunability, and desirable properties for applications such as polymer solar cells. In this study, the use of directing-groups to facilitate C-H activation is also explored, since one of the monomers for PDCBT contains ester-functionalities that may possess directing-group capabilities. It is found that these directing-groups are likely activating distal C-H bonds, and so the scope of this reaction is explored to determine how the structure and electronic properties of the coupling partner influence the polymerization outcome with regards to defect formation. ❧ In Chapter 4, the application of more earth abundant transition metal catalysts, such as those containing copper, are developed. Specifically, conditions that use a Cu-phenanthroline catalyst. The influence of the reaction solvent, base, and temperature on the polymerization outcome is explored, and the optimal conditions are applied to range of polymer architectures. It is found that the desired conjugated polymer structure is prepared with no observable defects, as evidenced through structural characterization. However, the conditions are reliant on the use of 50 mol% of catalyst, which is significantly higher than most methods for Pd-catalyzed DArP. This however provides the first report of conjugated donor-acceptor copolymers being synthesized using DArP with a Cu-catalyst. ❧ In Chapter 5, the conditions developed in Chapter 4 are applied towards the synthesis of PDOF-OD, which is a luminescent polymer noted for its potential application in OLEDs. This polymer has been extensively studied and very well characterized, offering a nice model for exploring the broader scope of Cu-catalysed DArP. Through the optimization of the base, concentration, and time, the Cu-catalyst loading was lowered from 50 mol% to 5 mol%, without significant sacrifice to Mₙ and yield. This presents Cu-catalysed DArP as a potentially viable alternative to Pd-catalysed DArP , setting the precedent for much future work within the field of sustainable conjugated polymer synthesis.

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Creator Pankow, Robert Mark (author)

Core Title Improving the sustainability of conjugated polymer synthesis via direct arylation polymerization

School College of Letters, Arts and Sciences

Degree Doctor of Philosophy

Degree Program Chemistry

Publication Date 06/04/2020

Defense Date 03/30/2020

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Tag conjugated polymer,OAI-PMH Harvest,organic electronics,polymer,polymer synthesis,solar cell,sustainable chemistry

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Advisor Thompson, Barry (committee chair), Gupta, Malancha (committee member), Prakash, Surya (committee member)

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