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Non-conjugated pendant electroactive polymers as potential materials for opto-electronic applications

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Non-conjugated pendant electroactive polymers as potential materials for opto-electronic applications

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Content
NON-CONJUGATED PENDANT ELECTROACTIVE POLYMERS AS POTENTIAL
MATERIALS FOR OPTO-ELECTRONIC APPLICATIONS

by
Sanket Samal

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

May 2022

Copyright 2022 Sanket Samal
ii

TABLE OF CONTENTS

Acknowledgments ............................................................................................................. v
Dedication ........................................................................................................................ vii
List of Tables .................................................................................................................. viii
List of Figures ................................................................................................................... ix
List of Schemes .............................................................................................................. xxii
Abstract ......................................................................................................................... xxiii
Chapter 1: Recent Advances in Non-Conjugated Pendant Electroactive Polymers
(NCPEPs) for Opto-Electronic Applications ............................................. 1
1.1 Introduction ....................................................................................... 1
1.2 Non-Conjugated Pendant Electroactive Polymers (NCPEPs) ...... 4
1.3 Simple NCPEPs and their potential ................................................. 4
1.4 Development of NCPEPs for different applications ....................... 5
1.5 Synthesis of NCPEPs ......................................................................... 8
1.6 Designing of functional NCPEPs.................................................... 13
1.7 Stereoregularity in NCPEPs ........................................................... 14
1.8 Conclusion and Outlook ................................................................. 17
1.9 References ........................................................................................ 18
Chapter 2: Converging the Hole Mobility of Poly(2-N-carbazolylethyl acrylate) with
Conjugated Polymers by Tuning Isotacticity ........................................... 35
2.1 Introduction ..................................................................................... 35
2.2 Experimental .................................................................................... 38
2.3 Results and Discussion .................................................................... 40
2.4 Conclusions ...................................................................................... 46
2.5 References ........................................................................................ 47

iii

Chapter 3: Influence of Alkyl Chain Spacer Length on the Charge Carrier Mobility
of Isotactic Poly (N-carbazolylalkyl acrylates) ......................................... 55
3.1 Introduction ..................................................................................... 55
3.2 Experimental .................................................................................... 59
3.3 Results and Discussion .................................................................... 60
3.4 Conclusion ........................................................................................ 68
3.5 References ........................................................................................ 69
Chapter 4: Contrasting the Charge Carrier Mobility of Isotactic, Syndiotactic, and
Atactic Poly((N-carbazolylethylthio)propyl methacrylate) ..................... 79
4.1 Introduction ..................................................................................... 79
4.2 Experimental .................................................................................... 82
4.3 Results and Discussion .................................................................... 86
4.4 Conclusion ........................................................................................ 92
4.5 References ........................................................................................ 93
Bibliography .................................................................................................................. 102
Appendices ..................................................................................................................... 103
Appendix A .................................................................................................. 103
A.1 General .......................................................................................... 103
A.2 Synthesis ........................................................................................ 106
A.3 Polymer NMR ............................................................................... 108
A.4 UV-Vis Spectroscopy .................................................................... 113
A.5 X-Ray Diffraction ......................................................................... 114
A.6 Polymer Mobility Data ................................................................. 116
A.7 Differential Scanning Calorimetry (DSC) .................................. 117
A.8 Cyclic Voltammetry (CV) ............................................................ 118
A.9 References ..................................................................................... 120
Appendix B .................................................................................................. 121
B.1 General ........................................................................................... 121
B.2 Synthesis ........................................................................................ 124
B.3 NMR Spectroscopy ....................................................................... 129
B.4 UV -Vis Spectroscopy ................................................................... 137
iv

B.5 X-Ray Diffraction ......................................................................... 138
B.6 Photoluminescence ........................................................................ 139
B.7 Hole Mobility ................................................................................. 140
B.8 Cyclic Voltammetry ...................................................................... 142
B.9. DSC ............................................................................................... 149
B.10. Simulations ................................................................................. 155
B.11. References ................................................................................... 188
Appendix C .................................................................................................. 189
C.1 General .......................................................................................... 189
C.2 Synthesis ........................................................................................ 192
C.3 NMR Spectroscopy ....................................................................... 200
C.4 Thermal Gravimetric Analysis (TGA) ....................................... 208
C.5 UV -Vis Spectroscopy ................................................................... 209
C.6 X-Ray Diffraction ......................................................................... 210
C.7 Differential Scanning calorimetry (DSC) ................................... 211
C.8 Hole Mobilities .............................................................................. 215
C.9 Atomic Force Microscopy (AFM) ............................................... 217
C.10 Cyclic Voltammetry .................................................................... 219
C.11 Simulations .................................................................................. 221
C.12 References ................................................................................... 232

v

Acknowledgments
I would first like to thank my family for their support and guidance throughout my
life. Specifically, to my father and mother 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. Richard
Brutchey and Prof. Malancha Gupta for agreeing to serve on my qualifying examination,
and defense committees.
I would next like to thank my uncle, Prof. Shashadhar Samal, for instilling a sense
of curiosity and wonder about chemistry that continues to grow. You motivated me to
pursue my graduate studies through your support and guidance. Also, much gratitude is
due to my M.S. advisor, Prof. V. Krishnan. 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, Dr. Elizabeth Melenbrink, and Dr.
Robert Pankow, 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
vi

Robert, you have become great friends, and I look forward to the continued growth of our
friendship. Liwei, Pratyusha, Qingpei, Negar, Alex, and Melanie, you have all been great
colleagues and friends. Alex, I especially owe you much thanks since it was through your
helpful discussions and hard work we were able to further push the boundaries of NCPEPs.
I truly look forward to seeing what more you can accomplish. Robert and Liwei, you both
have been exceptional colleagues and friends. I thoroughly enjoyed your company, and
you were always there for me at the time of need. The work in this dissertation would not
have been possible without the assistance of the following individuals: Alexander Schmitt
(monomer synthesis, and polymer synthesis in Chapters 4).
Abegail, Caroline, Bryce, Keying, Nick, Kevin, Antonina, Thomas, Robert,
Savannah, 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, Mami, Geo, and
Martin, thank you for the great friendship over these years.
To my Adams House roomates Seda, Aneesh, Jeremiah and Rachael, I have made
many journies throughout my stay at the Adams House with you all, and I look forward to
see you graduate soon. Also, sincere appreciation to Lucia, for constantly motivating me
to do science, and to be a great roomate, friend, and late night movie companion.

vii

Dedication

To my family and friends.

viii

List of Tables
Table 2.1 Reaction Conditions, Yield, Molecular Weights, Ð, Dyad and Triad isotacticty
and SCLC mobilities for family of isotactic PCzEA. ....................................................... 41
Table 3.1 Polymer Yields/Conversions, Molecular Weights, Ð, Dyad Isotacticity and
SCLC mobilities for family of isotactic PCzXA polymers with different alkyl chain
spacers. .............................................................................................................................. 61
Table 4.1 Polymer Yields/Conversions, Molecular Weights, Ð, Triad and pentad tacticity
and SCLC mobilities for the family of PCzETPMA polymers. ....................................... 85
Table A.1 Polymer GIXRD data.. .................................................................................. 115
Table A.2 Hole mobilities of PCzEA polymers in thin films spin coated from 2% Toluene
in chloroform (7 mg/ml) and annealed at 105
0
C for 30min. Results are an average of at-
least 6 pixels.. .................................................................................................................. 116
Table A.3 Electrochemical HOMO values, Optical Band Gaps, and Thermal properties of
family of isotactic PCzEA.. ............................................................................................ 119
Table B.1 Polymer yield and Molecular Weights for Polymers 6a – 6d.. ..................... 126
Table B.2 Electrochemical HOMO values for transesterified polymers.. ..................... 148
Table C.1 Electrochemical HOMO values for polymer 6a – 9a. ................................... 221

ix

List of Figures
Figure 1.1 Examples of some CPs currently developed for different applications. ........... 1
Figure 1.2 Development of NCPEPs in the last decade as host materials in OLEDs.. ...... 5
Figure 1.3 Development of NCPEPs in the last decade as emitting materials in OLEDs.. 6
Figure 1.4 Development of NCPEPs as hole transport material in Perovskite PVs. ......... 7
Figure 1.5 General backbone functionalities used for synthesis of NCPEPs.. .................. 9
Figure 1.6 Post-polymerization functionalization techniques used in the synthesis of
NCPEPs............................................................................................................................. 10
Figure 1.7 Thermodynamic phase segregation in block co-polymer NCPEP.. ............... 13
Figure 1.8 Effect of isotacticity on charge carrier mobility of NCPEP ........................... 15
Figure 2.1 NMR spectra of ~95% dyad Isotacticity PCzEA (4i) a) 1H NMR with formula
for dyad tacticity (peak at 1.28ppm is from grease) b) 13C NMR with formula for triad
tacticity... ........................................................................................................................... 42
Figure 2.2 Relationship of hole mobility of as cast and annealed films with the tacticity of
the polymers.. .................................................................................................................... 44
Figure 2.3 Emission profile of the family of PCzEA films a) unannealed b) annealed at
150
0
C for 30mins.. ............................................................................................................ 45
Figure 3.1 Structure of the NCPEP poly(2-N-carbazolylethyl acrylate (PCzEA) indicating
the structural variables (left) and an isotactic polymer PCzEA (right).. ........................... 56
Figure 3.2 Relationship of hole mobility of as cast and annealed films for the polymers
with different spacer chain lengths. .................................................................................. 63
Figure 3.3 DFT optimized structures of atactic PCzEA and isotactic PCzEA (with inset
showing helical backbone) (top) and isotactic polymer chains of PCzXA with increasing
x

spacer chain length (bottom). The polymer backbones are highlighted and all polymers
have 40 repeat units.. ........................................................................................................ 65
Figure 3.4 a) MD simulations of 64 chains of PCzHA (six-carbon spacer) packed into a
thin film configuration after annealing. b) The stacking of different carbazole units from
multiple chains showing short range ordering (blue labelling).. ...................................... 67
Figure 4.1 Structural features impacting properties in NCPEPs: Backbone structure, spacer
length, pendant group and stereoregularity.. ..................................................................... 80
Figure 4.2 Effect of annealing on the hole mobility of PCzETPMA polymers with different
tacticity.. ............................................................................................................................ 87
Figure 4.3 (a) HOMO and LUMO of PCzETPMA repeating unit. (b) PL spectra of
PCzETPMA polymers as-cast films. (c) PL spectra of PCzETPMA polymers films after
annealing at 210
0
C for 30 mins.. ...................................................................................... 89
Figure 4.4 (a) DFT – optimized structures of PCzETPMA polymers with 40 repeating
units and highlighted polymer backbone. (b) Mapping of carbazole moieties from MD
simulated thin films of 64 chains showing short range ordering (blue labelling). ........... 91
Figure A.1
1
H NMR of PCzEA in CDCl3 at 50 °C.. ...................................................... 108
Figure A.2
13
C NMR of PCzEA in CDCl3 at 50 °C.. .................................................... 109
Figure A.3
13
C NMR of PCzEA in CDCl3 at 50 °C, zoomed from 30-70 ppm.. .......... 110
Figure A.4 2D HSQC NMR of PCzEA with m = 50.7. From the single bond correlation
spectra, we can see that peak at 34.3 ppm in
13
C NMR has a strong correlation with peak
at 1.15 ppm in
1
H NMR.. ................................................................................................ 111
xi

Figure A.5 2D HSQC NMR of PCzEA with m = 94.7. From the single bond correlation
spectra, we can see that peak at 33.45 ppm in
13
C NMR has a strong correlation with peaks
at 0.87 ppm and 1.37 ppm in
1
H NMR.. ......................................................................... 112
Figure A.6 Absorption profile of PCzEA films, a) non-annealed, b) annealed at 150oC for
30min.. ............................................................................................................................ 113
Figure A.7 X-Ray diffraction pattern for PCzEA film after annealing at 150
0
C for 30min.
Peak at 0.1 and 0.5 (2θ) is the direct beam from the instrument.. .................................. 114
Figure A.8 DSC trace of PCzEA polymers (4a – 4i).. ................................................... 117
Figure A.9 a) Atactic PCzEA polymer (m = 45.5) b) Isotactic PCzEA polymer (m = 94.7).
The rest of the polymers gave similar spectra. ............................................................... 118
Figure B.1
1
H NMR of 75% isotactic poly(methyl acrylate) (9a).. ............................... 129
Figure B.2
1
H NMR of 87% isotactic poly(methyl acrylate) (9b).. ............................... 129
Figure B.3 Calculation of Isotacticity from
1
H NMR for 9a and 9b.. ........................... 130
Figure B.4
1
H NMR spectra of 87% isotactic PMA (9b) and trans-esterified PCzEA (10b).
......................................................................................................................................... 130
Figure B.5
1
H NMR of 87% isotactic 2C-spacer-spacerafter transesterification (10b). 131
Figure B.6
1
H NMR of 87% isotactic 4C-spacer-spacerafter transesterification (11b). 131
Figure B.7
1
H NMR of 87% isotactic 6C-spacer-spacerafter transesterification (12b). 132
Figure B.8
1
H NMR of 87% isotactic 8C-spacer-spacerafter transesterification (13b). 132
Figure B.9
1
H NMR of 87% isotactic 10C-spacer-spacerafter transesterification (14b).
......................................................................................................................................... 133
Figure B.10
1
H NMR of 87% isotactic 12C-spacer-spacerafter transesterification (15b).
......................................................................................................................................... 133
xii

Figure B.11
1
H NMR of 75% isotactic 2C-spacer-spacerafter transesterification (10a).
......................................................................................................................................... 134
Figure B.12
1
H NMR of 75% isotactic 4C-spacer-spacerafter transesterification (11a).
......................................................................................................................................... 134
Figure B.13
1
H NMR of 75% isotactic 6C-spacer-spacerafter transesterification (12a).
......................................................................................................................................... 135
Figure B.14
1
H NMR of 75% isotactic 8C-spacer-spacerafter transesterification (13a).
......................................................................................................................................... 135
Figure B.15
1
H NMR of 75% isotactic 10C-spacer-spacerafter transesterification (14a).
......................................................................................................................................... 136
Figure B.16
1
H NMR of 75% isotactic 12C-spacer-spacerafter transesterification (15a).
......................................................................................................................................... 136
Figure B.17 Annealed 75% isotactic polymers(UV). .................................................... 137
Figure B.18 Annealed 87% Isotactic polymers(UV). .................................................... 137
Figure B.19 Annealed 75% Isotactic polymers(XRD).. ................................................ 138
Figure B.20 Annealed 87% Isotactic polymers(XRD).. ................................................ 138
Figure B.21 Annealed 75% Isotactic polymers(PL). ..................................................... 139
Figure B.22 Annealed 87% Isotactic polymers(PL). ..................................................... 139
Figure B.23 Unannealed 75% Isotactic polymers(Mobility).. ....................................... 140
Figure B.24 Annealed 75% Isotactic polymers(Mobility). ............................................ 140
Figure B.25 Unannealed 87% Isotactic polymers(Mobility). ........................................ 141
Figure B.26 Unannealed 75% Isotactic polymers(Mobility). ........................................ 141
Figure B.27 CV scan of 75% isotactic 2C-spacer after transesterification (10a). ......... 142
xiii

Figure B.28 CV scan of 87% isotactic 2C-spacer after transesterification (10b). ......... 142
Figure B.29 CV scan of 75% isotactic 4C-spacer after transesterification (11a).. ........ 143
Figure B.30 CV scan of 87% isotactic 4C-spacer after transesterification (11b).. ........ 143
Figure B.31 CV scan of 75% isotactic 6C-spacer after transesterification (12a).. ........ 144
Figure B.32 CV scan of 87% isotactic 6C-spacer after transesterification (12b).. ........ 144
Figure B.33 CV scan of 75% isotactic 8C-spacer after transesterification (13a).. ........ 145
Figure B.34 CV scan of 87% isotactic 8C-spacer after transesterification (13b).. ........ 145
Figure B.35 CV scan of 75% isotactic 10C-spacer after transesterification (14a).. ...... 146
Figure B.36 CV scan of 87% isotactic 10C-spacer after transesterification (14b).. ...... 146
Figure B.37 CV scan of 75% isotactic 12C-spacer after transesterification (15a).. ...... 147
Figure B.38 CV scan of 87% isotactic 12C-spacer after transesterification (15b).. ...... 147
Figure B.39 DSC scan of 75% isotactic 2C-spacer after transesterification (10a).. ...... 149
Figure B.40 DSC scan of 75% isotactic 4C-spacer after transesterification (11a). ....... 149
Figure B.41 DSC scan of 75% isotactic 6C-spacer after transesterification (12a).. ...... 150
Figure B.42 DSC scan of 75% isotactic 8C-spacer after transesterification (13a).. ...... 150
Figure B.43 DSC scan of 75% isotactic 10C-spacer after transesterification (14a).. .... 151
Figure B.44 DSC scan of 75% isotactic 12C-spacer after transesterification (15a).. .... 151
Figure B.45 DSC scan of 87% isotactic 2C-spacer after transesterification (10b).. ...... 152
Figure B.46 DSC scan of 87% isotactic 4C-spacer after transesterification (11b).. ...... 152
Figure B.47 DSC scan of 87% isotactic 6C-spacer after transesterification (12b).. ...... 153
Figure B.48 DSC scan of 87% isotactic 8C-spacer after transesterification (13b).. ...... 153
Figure B.49 DSC scan of 87% isotactic 10C-spacer after transesterification (14b).. .... 154
Figure B.50 DSC scan of 87% isotactic 12C-spacer after transesterification (15b).. .... 154
xiv

Figure B.51 Relaxation of individual polymer chain from starting configuration at 0 K to
300 K. .............................................................................................................................. 158
Figure B.52 Formation of thin film morphology at 300 K. ........................................... 159
Figure B.53 Formation of thin film morphology at 300 K and thermal annealing
simulation.. ...................................................................................................................... 160
Figure B.54 Optimized structure for atactic polymer with 2 carbon spacer and 20 repeating
units.. ............................................................................................................................... 160
Figure B.55 Optimized structure for atactic polymer with 2 carbon spacer and 40 repeating
units.. ............................................................................................................................... 161
Figure B.56 Optimized structure for isotactic polymer with 2 carbon spacer and 20
repeating units.. ............................................................................................................... 161
Figure B.57 Optimized structure for isotactic polymer with 2 carbon spacer and 40
repeating units.. ............................................................................................................... 162
Figure B.58 Thin layer MD structure for atactic polymer with 2 carbon spacer at room-
temp................................................................................................................................. 162
Figure B.59 Thin layer MD structure for atactic polymer with 2 carbon spacers at room-
temp where all the carbazole moieties are highlighted.. ................................................. 163
Figure B.60 Thin layer MD structure for atactic polymer with 2 carbon spacers after
annealing. ........................................................................................................................ 163
Figure B.61 Thin layer MD structure for atactic polymer with 2 carbon spacers after
annealing where all the carbazole moieties are highlighted.. ......................................... 164
Figure B.62 Thin layer MD structure for isotactic polymer with 2 carbon spacers at room-
temp................................................................................................................................. 164
xv

Figure B.63 Thin layer MD structure for isotactic polymer with 2 carbon spacers at room-
temp where all the carbazole moieties are highlighted.. ................................................. 165
Figure B.64 Thin layer MD structure for isotactic polymer with 2 carbon spacers after
annealing.. ....................................................................................................................... 165
Figure B.65 Thin layer MD structure for isotactic polymer with 2 carbon spacers after
annealing where all the carbazole moieties are highlighted.. ......................................... 166
Figure B.66 Optimized structure for isotactic polymer with 4 carbon spacer and 20
repeating units. ................................................................................................................ 166
Figure B.67 Optimized structure for isotactic polymer with 4 carbon spacer and 40
repeating units.. ............................................................................................................... 167
Figure B.68 Thin layer MD structure for isotactic polymer with 4 carbon spacers at room-
temp................................................................................................................................. 167
Figure B.69 Thin layer MD structure for isotactic polymer with 4 carbon spacers at room-
temp where all the carbazole moieties are highlighted.. ................................................. 168
Figure B.70 Thin layer MD structure for isotactic polymer with 4 carbon spacers after
annealing.. ....................................................................................................................... 168
Figure B.71 Thin layer MD structure for isotactic polymer with 4 carbon spacers after
annealing where all the carbazole moieties are highlighted.. ......................................... 169
Figure B.72 Optimized structure for isotactic polymer with 6 carbon spacer and 20
repeating units ................................................................................................................. 169
Figure B.73 Optimized structure for isotactic polymer with 6 carbon spacer and 40
repeating units. ................................................................................................................ 170
xvi

Figure B.74 Thin layer MD structure for isotactic polymer with 6 carbon spacers at room-
temp................................................................................................................................. 170
Figure B.75 Thin layer MD structure for isotactic polymer with 6 carbon spacers at room-
temp where all the carbazole moieties are highlighted.. ................................................. 171
Figure B.76 Thin layer MD structure for isotactic polymer with 6 carbon spacers after
annealing.. ....................................................................................................................... 171
Figure B.77 Thin layer MD structure for isotactic polymer with 6 carbon spacers after
annealing where all the carbazole moieties are highlighted. .......................................... 172
Figure B.78 Optimized structure for isotactic polymer with 8 carbon spacer and 20
repeating units. ................................................................................................................ 172
Figure B.79 Optimized structure for isotactic polymer with 8 carbon spacer and 40
repeating units.. ............................................................................................................... 173
Figure B.80 Thin layer MD structure for isotactic polymer with 8 carbon spacers at room-
temp................................................................................................................................. 173
Figure B.81 Thin layer MD structure for isotactic polymer with 8 carbon spacers at room-
temp where all the carbazole moieties are highlighted.. ................................................. 174
Figure B.82 Thin layer MD structure for isotactic polymer with 8 carbon spacers after
annealing.. ....................................................................................................................... 174
Figure B.83 Thin layer MD structure for isotactic polymer with 8 carbon spacer after
annealing where all the carbazole moieties are highlighted. .......................................... 175
Figure B.84 Optimized structure for isotactic polymer with 10 carbon spacer and 20
repeating units.. ............................................................................................................... 175
xvii

Figure B.85 Optimized structure for isotactic polymer with 10 carbon spacer and 40
repeating units.. ............................................................................................................... 176
Figure B.86 Thin layer MD structure for isotactic polymer with 10 carbon spacers at room-
temp................................................................................................................................. 176
Figure B.87 Thin layer MD structure for isotactic polymer with 10 carbon spacers at room-
temp where all the carbazole moieties are highlighted.. ................................................. 177
Figure B.88 Thin layer MD structure for isotactic polymer with 10 carbon spacers after
annealing.. ....................................................................................................................... 177
Figure B.89 Thin layer MD structure for isotactic polymer with 10 carbon spacers after
annealing where all the carbazole moieties are highlighted.. ......................................... 178
Figure B.90 Optimized structure for isotactic polymer with 12 carbon spacer and 20
repeating units.. ............................................................................................................... 178
Figure B.91 Optimized structure for isotactic polymer with 12 carbon spacer and 40
repeating units.. ............................................................................................................... 179
Figure B.92 Thin layer MD structure for isotactic polymer with 12 carbon spacers at room-
temp................................................................................................................................. 179
Figure B.93 Thin layer MD structure for isotactic polymer with 12 carbon spacers at room-
temp where all the carbazole moieties are highlighted. .................................................. 180
Figure B.94 Thin layer MD structure for isotactic polymer with 12 carbon spacers after
annealing.. ....................................................................................................................... 180
Figure B.95 Thin layer MD structure for isotactic polymer with 12 carbon spacers after
annealing where all the carbazole moieties are highlighted.. ......................................... 181
xviii

Figure B.96 Thin layer MD structure for isotactic polymer with 2 carbon spacers at room
temperature indicating individual chains.. ...................................................................... 181
Figure B.97 Thin layer MD structure for isotactic polymer with 2 carbon spacers after
annealing indicating individual chains.. .......................................................................... 182
Figure B.98 Thin layer MD structure for isotactic polymer with 4 carbon spacers at room
temperature indicating individual chains.. ...................................................................... 182
Figure B.99 Thin layer MD structure for isotactic polymer with 4 carbon spacers after
annealing indicating individual chains. ........................................................................... 183
Figure B.100 Thin layer MD structure for isotactic polymer with 6 carbon spacers at room
temperature indicating individual chains. ....................................................................... 183
Figure B.101 Thin layer MD structure for isotactic polymer with 6 carbon spacers after
annealing indicating individual chains.. .......................................................................... 184
Figure B.102 Thin layer MD structure for isotactic polymer with 8 carbon spacers at room
temperature indicating individual chains. ....................................................................... 184
Figure B.103 Thin layer MD structure for isotactic polymer with 8 carbon spacers after
annealing indicating individual chains. ........................................................................... 185
Figure B.104 Thin layer MD structure for isotactic polymer with 10 carbon spacers at
room temperature indicating individual chains............................................................... 185
Figure B.105 Thin layer MD structure for isotactic polymer with 10 carbon spacers after
annealing indicating individual chains. ........................................................................... 186
Figure B.106 Thin layer MD structure for isotactic polymer with 12 carbon spacers at
room temperature indicating individual chains............................................................... 186
xix

Figure B.107 Thin layer MD structure for isotactic polymer with 12 carbon spacers after
annealing indicating individual chains. ........................................................................... 187
Figure C.1
1
H-NMR of compound 2.. ........................................................................... 200
Figure C.2
1
H NMR of compound 3. ............................................................................. 200
Figure C.3
1
H NMR of compound 4. ............................................................................. 201
Figure C.4
1
H NMR of polymer 6. ................................................................................ 201
Figure C.5
1
H NMR of polymer 7. ................................................................................ 202
Figure C.6
1
H NMR of polymer 8.. ............................................................................... 202
Figure C.7
1
H NMR of polymer 9.. ............................................................................... 203
Figure C.8
13
C NMR of polymer 6.. .............................................................................. 203
Figure C.9
13
C NMR of polymer 7. ............................................................................... 204
Figure C.10
13
C NMR of polymer 8. ............................................................................. 204
Figure C.11
13
C NMR of polymer 9. ............................................................................. 205
Figure C.12 Sample calculation of triad tacticity from
1
H NMR for polymer 6.. ......... 205
Figure C.13 Sample calculation of pentad tacticity from
13
C NMR for polymer 6.. ..... 206
Figure C.14
1
H NMR for polymer 6a. ........................................................................... 206
Figure C.15
1
H NMR for polymer 7a.. .......................................................................... 207
Figure C.16
1
H NMR of polymer 8a. ............................................................................ 207
Figure C.17
1
H NMR of polymer 9a. ............................................................................ 208
Figure C.18 TGA plots of PCzETPMA polymers. ........................................................ 208
Figure C.19 As cast thin films of polymers 6a – 9a(UV).............................................. 209
Figure C.20 Annealed thin films of polymers 6a – 9a(UV) .......................................... 209
Figure C.21 As cast thin films of polymers 6a – 9a(XRD). .......................................... 210
xx

Figure C.22 Annealed thin films of polymers 6a – 9a(XRD). ...................................... 210
Figure C.23 DSC scan of polymer 6. ............................................................................. 211
Figure C.24 DSC scan of polymer 7. ............................................................................. 211
Figure C.25 DSC scan of polymer 8.. ............................................................................ 212
Figure C.26 DSC scan of polymer 9.. ............................................................................ 212
Figure C.27 DSC scan of polymer 6a.. .......................................................................... 213
Figure C.28 DSC scan of polymer 7a. ........................................................................... 213
Figure C.29 DSC scan of polymer 8a.. .......................................................................... 214
Figure C.30 DSC scan of polymer 9a.. .......................................................................... 214
Figure C.31 Polymer 6a with different annealing conditions(Mobility). ...................... 215
Figure C.32 Polymer 7a with different annealing conditions(Mobility). ...................... 215
Figure C.33 Polymer 8a with different annealing conditions(Mobility). ...................... 216
Figure C.34 Polymer 9a with different annealing conditions(Mobility) ....................... 216
Figure C.35 Polymers 6a topology image. .................................................................... 217
Figure C.36 Polymers 7a topology image. .................................................................... 217
Figure C.37 Polymers 8a topology image. .................................................................... 218
Figure C.38 Polymers 9a topology image. .................................................................... 218
Figure C.39 CV scan of polymer 6a.. ............................................................................ 219
Figure C.40 CV scan of polymer 7a. ............................................................................. 219
Figure C.41 CV scan of polymer 8a. ............................................................................. 220
Figure C.42 CV scan of polymer 9a. ............................................................................. 220
Figure C.43 Optimized structure for atactic polymer with 20 repeating units. ............. 223
Figure C.44 Optimized structure for atactic polymer with 40 repeating units. ............. 223
xxi

Figure C.45 Optimized structure for isotactic polymer with 20 repeating units. .......... 224
Figure C.46 Optimized structure for isotactic polymer with 40 repeating units.. ......... 224
Figure C.47 Optimized structure for isotactic polymer with 20 repeating units. .......... 225
Figure C.48 Optimized structure for isotactic polymer with 40 repeating units.. ......... 225
Figure C.49 Thin layer MD structure for atactic polymer at room-temp. ..................... 226
Figure C.50 Thin layer MD structure for atactic polymer at room-temp where all the
carbazole moieties are highlighted.................................................................................. 226
Figure C.51 Thin layer MD structure for atactic polymer after annealing. ................... 227
Figure C.52 Thin layer MD structure for atactic polymer after annealing where all the
carbazole moieties are highlighted.................................................................................. 227
Figure C.53 Thin layer MD structure for isotactic polymer at room-temp. .................. 228
Figure C.54 Thin layer MD structure for isotactic polymer at room-temp where all the
carbazole moieties are highlighted.................................................................................. 228
Figure C.55 Thin layer MD structure for isotactic polymer after annealing. ................ 229
Figure C.56 Thin layer MD structure for isotactic polymer after annealing where all the
carbazole moieties are highlighted.................................................................................. 229
Figure C.57 Thin layer MD structure for syndiotactic polymer at room-temp. ............ 230
Figure C.58 Thin layer MD structure for syndiotactic polymer at room-temp where all the
carbazole moieties are highlighted.................................................................................. 230
Figure C.59 Thin layer MD structure for syndiotactic polymer after annealing. .......... 231
Figure C.60 Thin layer MD structure for syndiotactic polymer after annealing where all
the carbazole moieties are highlighted. ........................................................................... 231

xxii

List of Schemes
Scheme 1.1 Architectures of polymeric electroactive materials. CPs with conjugated
backbone and NCPEPs with non-conjugated backbone.. ................................................... 3
Scheme 2.1 Synthesis of a) monomer 3, b) PCzEA polymer with different routes. ........ 37
Scheme 3.1 Synthesis of monomers, PMA polymers, and PCzXA polymers. ................ 60
Scheme 4.1 Synthesis of (a) Pendant group, (b) PAMA polymers, and (c) PCzETPMA
polymers. ........................................................................................................................... 84
Scheme A.1 Synthesis of PCzEA polymers. .................................................................. 106
Scheme B.1 Synthesis of monomers and PCzXA via direct polymerization. ................ 124

xxiii

Abstract

Non-Conjugated Pendant Electroactive Polymers as Potential
Materials for Opto-Electronic Applications

By
Sanket Samal
Doctor of Philosophy in Chemistry

Conjugated polymers (CPs) are widely explored for 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. However, despite outstanding performance in optoelectronic
xxiv

applications, CPs nonetheless are limited by several challenges. CPs have low solubility,
low environment stability, restricted mechanical properties and limited synthetic methods.
In the search for alternatives to CPs, non-conjugated pendant electroactive
polymers (NCPEPs) possess a great deal of potential for improving the physical and
mechanical properties of semiconducting polymers while retaining the optical and
electronic properties for optoelectronic applications. NCPEPs also offer access to the broad
range of controlled polymerization techniques for non-conjugated polymers that promise
access to highly tailored structures with diverse architectures. Despite the potential
advantages of NCPEPs, charge carrier mobilities are typically several orders of magnitude
lower than CPs, likely due to significant disorder and limited π-π stacking. In this
dissertation, strategies for improving the charge carrier mobility of NCPEPs are provided
through the alteration of structural parameters of the polymers, such as stereoregularity,
spacer length, and polymer backbone. Along with the structural paramters, new
polymerization techniques are also explored to synthesize functional NCPEPs with
improved charge carrier mobilities.
In Chapter 1, an overview of advancement of NCPEPs is detailed. This includes
descriptions of the synthesis of various stereoregular NCPEPs using radical, anionic and
post-polymerization functionalization techniques. Additionally, the effect of
stereoregularity on charge carrier mobility is presented, indicating that charge carrier
mobility is strongly affected by the stereoregularity, molecular weight, spacer length and
annealing conditions. This chapter summaraizes and provides the background for the work
detailed in Chapters 2-4.
xxv

In Chapter 2, the effect of side-chain isotacticity on hole mobility of NCPEPs was
explored using poly(2-N-carbazolylethylacrylate) (PCzEA) as a model polymer.
Specifically, polymers with dyad isotacticity ranging from m = 45% to m = 95% were
synthesized by several methods, including free radical and anionic polymerization. We
found that the hole mobility measured via the space charge limited current (SCLC)
technique increased proportionally with increasing isotacticity. This outcome is further
enhanced in thermally annealed samples, rivaling the well-known CP poly (3-
hexylthiophene) (P3HT). This is the first clear experimental evidence that the control of
side chain tacticity in NCPEPs can improve charge carrier mobility.
In Chapter 3, we investigate one of the vital structural variables of NCPEPs: the
flexible alkyl spacer that separates the electroactive pendant from the backbone. We
explore a straightforward post-polymerization functionalization to synthesize polymers
with high isotacticity, where the alkyl chain spacer is varied from 2 to 12 carbons. We
found that the hole mobility increased from 2 carbon spacer, resulting in the highest
mobility upon thermal annealing with a 4 carbon spacer for 75% isotactic polymers and
with a 6 carbon spacer for 87% isotactic polymers. DFT and MD simulations for such
NCPEPs indicated helical structures with intermolecular short-range π-stacking which are
affected by spacer chain length.
In Chapter 4, the broader influence of tacticity in NCPEPs is studied, using
poly((N-carbazolylethylthio)propyl methacrylate) (PCzETPMA) as a model polymer. We
explored the thiol-ene reaction as an efficient post-polymerization functionalization
method to achieve NCPEPs with high isotacticity and syndiotacticity. We found that a
stereoregular isotactic polymer showed 100 times increased hole mobility compared to
xxvi

both atactic and low molecular weight syndiotactic PCzETPMA. High molecular weight
syndiotactic PCzETPMA showed a dramatic increase in hole mobility when measured after
annealing at 210
o
C, which surpassed well-known CP P3HT. MD simulations indicated
short-range π-stacking in the case of stereoregular polymers. This represents the first report
of charge carrier mobilities in syndiotactic NCPEPs and demonstrates that the tacticity,
annealing conditions, and molecular weight of NCPEPs can strongly affect hole mobility.

1

Chapter 1: Recent Advances in Non-Conjugated Pendant Electroactive Polymers
(NCPEPs) for Opto-Electronic Applications

1.1 Introduction
Conjugated semiconducting polymers (CPs) were first reported by Heegar et al. in
1977,
1,2
which led to the Nobel Prize in Chemistry in 2000,
3
and are the cornerstone for the
rapid growth of organic electronics in the past decade. At present, CPs are explored for
many electronic applications, including organic light-emitting diodes (OLEDs),
4,5
organic
photovoltaics (OPVs),
6,7
organic field-effect transistors or organic electrochemical
transistors (OFETs/OECTs),
8,9
batteries,
10,11
and bioelectronics
12
due to their enhanced
optical, electrochemical, biocompatibility and mechanical properties. As shown in Figure
1.1, optimized CPs, along with the development of novel manufacturing technologies, have
led to high-performance devices.
10–16

Figure 1.1 Examples of some CPs currently developed for different applications.
2

A key feature for consideration in the design of semiconducting polymers for
optoelectronic application is the overall molecular structure of the polymer. The most
successful CPs studied to date have alternating strong electron donors and acceptors in the
main chain, which enhances the electron delocalization within the chain leading to a narrow
bandgap. CPs with such an optimized π-conjugated framework also lead to improved
morphological order in the solid-state, ultimately strengthening the charge carrier
mobility.
17,18
CPs additionally have suitable side chains, which help in the solubility and
processability of the polymers to achieve lightweight and inexpensive optoelectronic
devices.
19–22
Out of all the advantages of the CPs, enhanced charge carrier mobility is one
of the main performance metrics for any optoelectronic application.
23
With the
development of a superior π-conjugated framework, charge carrier mobility in CPs, when
measured in OFETs, has improved from 10
-6
cm
2
V
-1
s
-1
in the 1980s to >10 cm
2
V
-1
s
-1
,
exceeding the charge carrier mobility in thin film amorphous silicon.
24

Regardless of their exceptional performance in optoelectronics, CPs nevertheless
suffer from multiple challenges. Most of the state-of-the-art CPs depicted in Figure 1.1
have very complicated synthetic procedures, with some polymers taking more than 15 steps
to synthesize.
25,26
Most efficient CPs like PTB7-Th are very cost-inefficient with many
low-yielding steps and mostly synthesized via coupling reactions producing toxic side
products.
27
CPs generally have very poor environmental stability; consequently, the
efficiency of high-performance devices decreases rapidly over time when exposed to air
without any protection for longer time intervals.
28,29
CPs have limited mechanical
properties and, in some cases, also have low solubility.
30,31
CPs are also generally, opaque
across the visible spectrum due to extended conjugated backbones which can be
3

problematic for some applications.
32,33
Additionally, the majority of CPs synthesized today
are of low molecular weight with high polydispersity, affecting the optical and
electrochemical properties.
34

Taking into consideration all the shortcomings of CPs, there has been a great deal
of recent development in the field of non-conjugated polymers containing electroactive
units in the side chain which are suggested as alternatives for CPs. These non-conjugated
pendant electroactive polymers (NCPEPs) (Scheme 1.1) are desirable because of their high

Scheme 1.1 Architectures of polymeric electroactive materials. CPs with conjugated
backbone and NCPEPs with non-conjugated backbone.
stability and increased solubility.
35
NCPEPs can be synthesized with very high molecular
weights achieving 400 repeating units with ease and enhancing the optoelectronic
properties.
36,37
NCPEPs, because of their non-conjugated backbone, have superior
mechanical properties
38
and show great potential for flexible and stretchable optoelectronic
applications.
39,40
Additionally, NCPEPs are attractive because of their easy pendant
4

modification, diversity in accessible synthetic methodologies, and the potential for precise
control over hierarchical assemblies enabled by advanced architectures.
Here we detail the development of NCPEPs over the past decade for optoelectronic
application and provide perspective on major underlying issues that still need to be
addressed. Most of the initial NCPEPs were developed for application as hole and electron
transport materials; hence we will provide some background and discussion on how the
enhancement of charge carrier mobility is important for the development of new and
functional NCPEPs and provide suitable methodologies for the synthesis of new NCPEPs
for development of flexible and stretchable optoelectronic devices.
1.2 Non-Conjugated Pendant Electroactive Polymers (NCPEPs)
NCPEPs are analogous to side-chain liquid crystal polymer (SCLCPs).
41
The
properties of these polymers are strongly influenced by the structure of the main chain,
pendant group, spacer length, and stereoregularity.
42
Most importantly, NCPEPs with non-
conjugated polymer backbone have repeating units that are electrically isolated from each
other. Therefore the insulating backbones in NCPEPs is invariably attached with
electroactive pendant groups to impart charge transport (through space via π-π stacking)
and other optoelectronic properties to the polymer.
43

1.3 Simple NCPEPs and their potential
Poly(vinyl carbazole) (PVK) is one of the earliest examples of a pendant
electroactive polymer. Discovered to have photoconductive properties in 1957 by Helmut
et al.
44
PVK has been used for decades because vinyl carbazole and its derivatives are very
simple monomers, easy to functionalize and purify, and have enhanced photostability when
5

polymerized. The photoconductive nature of PVK derives from the fact that it forms
relatively stable radical cations upon photoexcitation, and the ability of the pendants to π-
π stack in a cofacial manner allows for efficient charge transport along the pendants.
45

Similarly another simple class of NCPEPs, that were a point of interest were the
poly(dibenzofulvenes) (PDBF), because similar to PVK, they also show the ability of π-π
stacking of the pendants in cofacial manner.
46
Although PVK has been broadly studied and
possesses many benefits over CPs, PVK, along with other non-stereoregular NCPEPs, have
very low hole mobilities of ~10
-7
cm
2
V
-1
s
-1
. Recently, Ozaki et al. showed that by
enhancing the stereoregularity of PVK backbone to high isotacticity, hole mobilities in
PVK can be enhanced to ~10
-6
cm
2
V
-1
s
-1
, but still lower than most CPs.
47
The effect of
isotacticity in NCPEPs has recently been extensively studied by Thompson et al.
48,49
and
is discussed later in the chapter. However, PDBF doesn’t suffer from such a problem,
achieving hole mobility of 10
-4
cm
2
V
-1
s
-1
, comparable to CPs.
50
The high hole mobility
of PDBF is solely attributed to efficient π-π stacking of the pendant units. These results
present insight on achieving high charge carrier mobilities in NCPEPs, which is also
supported by theoretical calculations and simulations.
51

1.4 Development of NCPEPs for different applications

Figure 1.2 Development of NCPEPs in the last decade as host materials in OLEDs.
6

The earliest relevant work in NCPEPs was done by Kim et al. in 2000, where PVK
was used as a host polymer for [Ir(ppy)3] in OLEDs, achieving external quantum efficiency
of 1.9% and peak luminance of 2500 cd/m
2
.
52
PVK was initially chosen as the host material
because the hole mobility in PVK is three orders of magnitude higher than its electron
mobility, hence acting as hole transport material. The use of NCPEPs as host materials in
OLEDs has received much attention in the last decade (Figure 1.2) with an enhancement
of external quantum efficiency to 22% using a donor-acceptor block co-polymer in a
thermally activated delayed fluorescence (TADF) OLED with a peak luminance of 4968
cd/m
2
.
53
Krueger et al. in 2010, showed that even though hole mobility (7 x 10
-6
cm
2
V
-1
s
-
1
) is orders of magnitude lower than CPs, they were able to achieve external quantum
efficiency of 7.9% using triphenylamine based NCPEPs as a host material in
phosphorescent OLEDs.
54
The low hole mobility of NCPEPs is compensated with a
relatively high glass transition temperature (Tg) of >200
o
C, which is a favorable property
for devices showing long lifetimes.

Figure 1.3 Development of NCPEPs in the last decade as emitting materials in OLEDs.
7

The above strategy of using NCPEPs is efficient in most cases but problematic in
some cases showing phase separation in OLED devices, resulting in non-uniform emission
and decreased emission intensity. Tokito et al., in 2003, synthesized NCPEP block
polymers where the Ir complexes are randomly copolymerized as electroactive pendant
units giving no phase separation and high external quantum efficiency of 9%.
55
Taking the
inspiration of including Ir emitter complexes in NCPEPs as electroactive pendant units, in
2004, Frechet et al. developed an NCPEP containing hole transporting, electron
transporting, and Pt-based emitter complexes as electroactive pendant units, which helped
them in easy processing and fabrication of near-white light-emitting diodes using spin
casting for the emissive layer.
56
This paved a pathway for fabricating, high efficiency, low
roll-off, and enhanced stability OLED devices (Figure 1.3).
57

Although a significant amount of work was done with OLEDs, NCPEPs are not
limited to OLED applications. Another optoelectronic application where the use of
NCPEPs is slowly expanding is in the field of Perovskite PVs (Figure 1.4).

Figure 1.4 Development of NCPEPs as hole transport material in Perovskite PVs.
8

Taking inspiration from use of NCPEPs as hole transport materials in OLEDs,
recently in 2017, Huang et al., synthesized a carbazole based NCPEP (PVCz-OMeDAD),
which can be used as an efficient dopant free hole transporting material for perovskite solar
cells.
58
The polymer worked very efficiently, giving hole mobility of 3.44 x 10
-4
cm
2
V
-1
s
-
1
when measured by the space charge limited current (SCLC) method. Use of NCPEPs in
perovskite PVs as hole transport materials helped to overcome the solubility issue faced in
previously-used small molecules like Spiro-OMeTAD
59
and is useful for achieving high
hole mobilities which were previously order of magnitude lower. Subsequently, after the
use of PVCz-OMeDAD as a dopant free hole transport material in perovskite PVs, people
started exploring NCPEPs with different electroactive pendant units as an efficient way to
achieve high hole mobility and therefore achieve efficiency as high as 18.45% with fill
factor (FF) as high as 81%, rivaling CPs.
60–62

1.5 Synthesis of NCPEPs
In NCPEPs, tailoring of the polymer architecture is easy to achieve by modifying
the monomer structure with a variety of polymerizable functionalities, such as vinyl,
acrylate, styrene, and norbornene derivatives (Figure 1.5). Moreover, as described earlier,
there are multiple synthetic techniques applicable to polymerize monomers functionalized
with pendant electroactive moieties, including polymerization via free radical
polymerization,
63–66
living anionic polymerization,
67–69
living cationic polymerization,
70

ring-opening metathesis polymerization,
71,72
atom transfer radical polymerization
(ATRP),
73
reversible addition-fragmentation transfer polymerization (RAFT),
74
and
nitroxide mediated polymerization (NMP).
75

9

Figure 1.5 General backbone functionalities used for synthesis of NCPEPs.
Even though non-conjugated polymers can be made by living polymerization
techniques to obtain precise molecular weights, dispersity, and end groups, leading to less
variation in the properties that influence performance in organic electronic devices,
optoelectronically active pendants tend to be more vulnerable to reaction conditions
mentioned above and can be difficult to polymerize using controlled or living methods.
Living anionic and cationic polymerization techniques often use initiators or catalysts that
can lead to side reactions with the functional groups present in the electroactive pendant
units and hence face problems for the efficient synthesis of such NCPEPs. Moreover,
achieving highly stereoregular NCPEPs is very challenging and such polymers are
generally synthesized via anionic and cationic polymerizations,
76,77
which are incompatible
with most optoelectronically active pendant units.
Another viable method to eliminate such a problem is use of a post-polymerization
functionalization method (Figure 1.6), which can be easily applied for obtaining functional
10

NCPEPs with electroactive pendants by using simple reactions like transesterification,
78

thiol-ene reactions
79
or “click” reactions.
80

Figure 1.6 Post-polymerization functionalization techniques used in the synthesis of
NCPEPs.

One of the early impressive post-polymerization reports was reported in 2003 by
Horiuchi et al.
36
They were able to synthesize a semi-rod-coil block co-polymer of styrene
and isoprene with oligothiophene modified side chains by esterifying a poly(styrene-b-
isoprene) block polymer with an oligothiophene derivative. This was impressive because
by synthesizing such block polymer, they were able to achieve a self-organized
microporous structure, which is almost impossible to achieve with conjugated polymers.
This hierarchical structure was unprecedented because the microporous structure was over
multiple length scales and was expected to have a wide range of applications in
optoelectronic devices. The block polymer was synthesized via anionic polymerization,
which is incompatible with the oligothiophene pendant unit; hence a post-polymerization
11

functionalization technique provided the most efficient and easiest way to achieve such an
impressive microporous structure.
Later around 2010, Thelakkat et al. published a comparative study of polyacrylates
with perylene diimide pendants, synthesized either through a direct-controlled NMP of
perylene diimide acrylate monomer or through a post-polymerization copper-catalyzed
click reaction.
81
They demonstrated that the polymerization kinetics were not first order,
and the polydispersity of the polymer increased with monomer conversion. The authors
credited the broad dispersity and unpredictable molecular weight of these polymers to poor
solubility of the perylene diimide pendant monomer. These molecular weights were
comparable to those obtained by post-polymerization, click reaction of the pendant
perylene diimide onto the non-conjugated backbone. However, the polymers obtained by
click reaction had low polydispersity with complete conversion in the post-polymerization
reaction verified by IR and showed almost no defect. The only problem that occurred with
the clicked polymer is that it contained a rigid triazole ring, which hampered the effective
packing of the perylene diimide showing lower crystallinity and hence low charge carrier
mobility.
Recently, we adopted the same post-polymerization functionalization technique,
where we attached N-alkylcarbazole (where the alkyl chain is of two to twelve carbons) to
an isotactic acrylate backbone by post-polymerization transesterification reaction of
isotactic poly(methyl acrylate) (PMA) with N-carbazolyl-alkyl-alcohol.
82
We used the
technique developed by Kim et al.,
78
where they transesterified PMA using ZnTac24 as the
catalyst in good conversion. We used the same catalyst to achieve a conversion higher
97%, with no side reaction (Chapter 3). This was particularly helpful in our case because
12

direct polymerization of N-carbazolyl-alkyl-acrylate gave us very low molecular weights
of 2 – 6 kg/mol as compared to transesterified polymers giving molecular weights of 25 –
35 kg/mol. Moreover, for the direct polymerization polymers, the molecular weight
decreased as the alkyl chain length increased, which was attributed to the intramolecular
interaction between the aromatic ring and the lithium counterion from the anionic
polymerization initiator. This post-polymerization functionalization method was very
effective and also avoided the formation of the rigid triazole ring mentioned previously.
Following post-polymerization transesterification, we also recently made NCPEPs using
another post-polymerization functionalization method by using the thiol-ene reaction. Such
reactions are more efficient than transesterification and helped us achieve greater than 99
% conversion when N-carbazolylethanethiol was reacted with poly(allyl methacrylate) to
get poly((N-carbazolylethylthio)propyl methacrylate) (Chapter 4). Moreover, these
reactions are very fast, with almost 100% conversion within 6 hours, and are very energy
efficient as the reaction is catalyzed by a photoinitiator using 300nm UV irradiation. Also,
this method helped us to achieve syndiotactic NCPEPs, which was one of the limitations
of the post-polymerization transesterification method.
The most efficient way of synthesizing NCPEPs is via direct polymerization using
techniques mentioned previously if the pendant units don’t have incompatibility with the
reaction condition or via post-polymerization functionalization techniques otherwise. In
the case of achieving highly stereoregular NCPEPs we have found, the post-polymerization
technique to be the most efficient one.

13

1.6 Designing of functional NCPEPs
A number of specifically designed NCPEPs have also been reported and these are
best embodied by the work of Thelakkat et al.
83,84
In 2004, Thelakkat et al. reported the
synthesis of poly(vinyl triphenylamine)-block-poly(perylene diimide acrylate),
85
showing
the first evidence of thermodynamic phase segregation (Figure 1.7) and demonstrated later
in 2006 that the single-component block co-polymer NCPEP can outperform a comparable
2-component blend in OPV devices.
86,87

Figure 1.7 Thermodynamic phase segregation in block co-polymer NCPEP
Even though single-component block co-polymer NCPEPs can outperform a
comparable 2-component blend in OPV devices, the efficiency achieved was less than 1%.
This low efficiency is primarily because these pendants are not optoelectronically active,
but another factor that impacts the efficiency is the low charge carrier mobilities,
specifically poly(vinyl triphenylamine) shows very low hole mobilities in the order of 10
-
14

9
-10
-8
cm
2
V
-1
s
-1
.
88
On the other hand, poly(perylene diimide acrylate) has very high
electron mobilities of 10
-3
-10
-2
cm
2
V
-1
s
-1
.
89
High electron mobility in case of
poly(perylene diimide acrylate) is primarily due to perylene diimide, which is known to
have very strong π-π stacking between the monomer units.
90

Through all of these studies, it has been shown that NCPEPs can achieve desired
morphology and stability. In the vast majority of NCPEPs, the charge carrier mobility
continues to suffer relative to that observed in fully conjugated polymers. It is clear from
the examples illustrated above that charge mobility is related to structure, and that
semiconducting polymer architecture can be leveraged to improve mobility, processability,
and morphology, amongst other properties. Even considering all these developments in the
field of NCPEPs, another avenue that remains relatively unexplored is the use of backbone
stereoregularity to control pendant alignment and influence charge carrier mobilities.

1.7 Stereoregularity in NCPEPs
The significance of stereoregularity in polymeric structures has been acknowledged
ever since the first report by Zoss et al. in 1948 discussing structural differences of
poly(vinyl ethers).
91
Stereoregularity affects many properties of the polymers such as
thermal (Tg, and Tm), mechanical, crystalline, electronic and optical.
92
In NCPEPs
multiple studies have been done to study the effect of stereoregularity on crystallinity,
mechanical and thermal properties of the polymer,
93,94
but the influence of stereoregularity
on charge carrier mobility is rarely studied.
In 1987 Uryu et al., for the first time showed that isotactic poly(N-carbazolylethyl
acrylate) (PCzEA) has six times higher hole mobility than its atactic counterpart.
69
Even
15

though this showed that isotacticity had an effect, it was not thoroughly studied. To fully
elucidate the effect of tacticity on NCPEPs, we synthesized a series of isotactic PCzEA
polymer with dyad isotacticity (m=45% to m=95%). We saw that, as the tacticity is
increased from 45% dyad isotacticity to 95% dyad isotacticity, hole mobility also increased
proportionally from 2.11 x 10
-6
cm
2
V
-1
s
-1
to 4.68 x 10
-5
cm
2
V
-1
s
-1
. The increase in hole
mobility is even further enhanced to 2.74 x 10
-4
cm
2
V
-1
s
-1
upon thermal annealing, which
rivaled the well-known conjugated polymer poly(3-hexylthiophene) (P3HT) (Figure
1.8).
48
This was the first clear experimental evidence that control of tacticity in NCPEPs
can improve charge carrier mobility (Chapter 2). Following in our footsteps, Ozaki et al
did similar work on PVK as discussed earlier.
47

Figure 1.8 Effect of isotacticity on charge carrier mobility of NCPEP.
16

Since this work was done on PCzEA, we wanted to see how the spacer length
influences the charge carrier mobility of NCPEP, we further recently reported a range of
isotactic polymer with different spacer units (2 Carbons to 12 Carbons), on two different
isotactic backbones of dyad isotacticity of m = 75% and m = 87% (Chapter 3). We
observed that the hole mobility increased from two carbon spacer, resulting in the highest
mobility upon thermal annealing with a four carbon spacer for 75% isotactic polymers and
with a six carbon spacer for 87% isotactic polymers.
49
We demonstrated an important role
of the spacer chain in influencing charge carrier mobility along with the stereoregularity of
NCPEPs.
Finally to study the full effect of stereoregularity on NCPEPs, recently we
efficiently synthesized, isotactic, atactic and syndiotactic Poly((N-
carbazolylethylthio)propyl methacrylate) (PCzETPMA) via thiol-ene post-polymerization
functionalization as mentioned earlier (Chapter 4). We found that a stereoregular isotactic
polymer showed ~100 times increased hole mobility as compared to both atactic and low
molecular weight syndiotactic PCzETPMA, achieving hole mobility of 2.19 x 10
-4
cm
2
V
-
1
s
-1
after annealing at 120

C. High molecular weight syndiotactic PCzETPMA gave ~10
times higher hole mobility than its atactic counterpart, comparable to isotactic PCzETPMA
after annealing at 150

C. Importantly, high molecular weight syndiotactic PCzEPTMA
showed a dramatic increase in hole mobility to 1.82 x 10
-3
cm
2
V
-1
s
-1
when measured after
annealing at 210

C, which surpassed the well-known conjugated polymer poly(3-
hexylthiophene) (P3HT) (µh = 4.51 x 10
-4
cm
2
V
-1
s
-1
). This is the very first report of charge
carrier mobilities in syndiotactic NCPEPs and demonstrates that the tacticity, annealing
conditions, and molecular weight of NCPEPs can strongly affect hole mobility of NCPEPs.
17

1.8 Conclusion and Outlook
While NCPEPs have been studied for several decades, in general, the charge carrier
mobility of these materials is quite low because charge transport is fundamentally restricted
to one dimension (i.e., along π-stacked pendants) as opposed to the three-dimensional
charge transport available in CPs. However, there is a strong effect of stereoregularity of
the NCPEP backbone on the charge carrier mobility, which forces the pendant units to be
π-stacked more efficiently, even though the pendant unit doesn’t have the inherent ability
to π-stacked. Our group has done extensive studies, proving that certainly, isotacticity
improves the charge carrier mobility in any NCPEP and the most optimized spacer length
is six carbon spacer. We showed that in NCPEPs, stereoregularity, spacer length, and
molecular weight are not independent and show a complex relationship, which in some
cases leads to charge carrier mobilities exceeding well-known CPs.
Such studies are relatively new, and more studies should be done to generalize the
idea of synthesizing stereoregular NCPEPs to achieve high charge carrier mobilities.
Nevertheless, this opens a new door for revisiting block co-polymers similar to ones
studied extensively by Thelakkat et al. and others by synthesizing them with a stereoregular
backbone. Such changes in those block co-polymers and improved hierarchical assemblies
could enhance the charge carrier mobilities to achieve functional NCPEPs with
optoelectronically active pendant units. Such stereoregular NCPEPs have the potential to
surpass CPs and perhaps replace them.

18

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35

Chapter 2: Converging the Hole Mobility of Poly(2-N-carbazolylethyl acrylate) with
Conjugated Polymers by Tuning Isotacticity

2.1 Introduction
Conjugated polymers (CPs) are organic macromolecules with continuous
alternating single and double bonds giving rise to delocalized π orbitals which results in
interesting optical and electronic properties. For this reason CPs are investigated for
multiple applications such as organic photovoltaics (OPVs),
1,2
organic field effect
transistors (OFETs),
3–5
organic light emitting diodes (OLEDs),
6–8
molecular imaging,
9,10

and electrochromics.
11,12
Among the above-mentioned applications, OPVs and OFETs are
evolving as a promising field for the low-cost manufacture of flexible and light weight
electronic devices.
13
A crucial factor for higher performance in OPVs and OFETs is high
charge carrier mobility.
14
In order to achieve high charge carrier mobilities, strategies to
improve intermolecular packing are commonly employed.
15
Hole mobilities as high as 23.7
cm
2
V
-1
s
-1
have been achieved in highly crystalline polymers such as PCDTPT,
16
as
measured in OFETs. However, for OPVs, hole mobilities of 10
-5
– 10
-3
cm
2
V
-1
s
-1
are typical
for state-of-the-art polymers as measured by the SCLC technique.
17
Despite their excellent
performance, CPs nevertheless suffer from several challenges including poor air stability,
18

limited mechanical properties due to high crystallinity and rigid polymer backbones,
19
low
molecular weight and limited polymerization, which are primarily based on step growth
methods.
20

To address these limitations, non-conjugated pendant electroactive polymers
(NCPEPs), which are based on a non-conjugated backbone and containing electroactive
36

units in the side chain, have been suggested as alternatives for CPs in the past, where high
stability,
21
wide-ranging electronic properties,
22,23
and high molecular weights
24,25
were
achieved. Additionally, living polymerization methods were used to achieve well-defined
block copolymers,
24
and indeed can also be used to target precise structure, molecular
weight, dispersity and end group control. Improved mechanical properties are also likely
accessible as many non-conjugated backbones are known to exhibit low tensile modulus.
26

Despite the potential advantages of NCPEPs, charge carrier mobilities are typically several
orders of magnitude lower than CPs,
27,28
likely due to significant disorder and limited π- π
stacking. This is in sharp contrast to small molecule systems which develop significant
levels of crystallinity and high mobilities (although are certainly lacking in mechanical
integrity, film forming ability and favorable blend formation).
29
As an exception to typical
low mobility (~10
-5
– 10
-7
cm
2
V
-1
s
-1
) from NCPEPs,
30
Thelakkat et al. were successful in
synthesizing non-conjugated polymers, having perylene bisimide pendants with long
carbon spacers from the backbone, achieving high electron mobilities of ~10
-3
cm
2
V
-1
s
-1
.
31

The improved mobility is likely a consequence of the long, flexible spacers allowing the
pendants to self-organize more effectively, although at the cost of more significantly
diluting the electroactive component.
As a method to address low charge carrier mobility, it has been theoretically
proposed that control over backbone stereoregularity in a simple NCPEP, poly(N-
vinylcarbazole) (PVK), could enhance intrachain π overlap and lead to improved hole
mobility,
32,33
beyond the 10
-6
– 10
-9
cm
2
V
-1
s
-1
that is typically observed.
28
The first
experimental evidence in support of this proposition was reported by Uryu et al. where they
showed that highly isotactic (m = ~97%) poly(2-N-carbazoylethyl acrylate) (PCzEA) had
37

a µh of 1.7 x 10
-5
cm
2
V
-1
s
-1
; being 6 times higher than the atactic polymer (3 x 10
-6
cm
2
V
-
1
s
-1
) when measured by a time of flight technique.
34
While this work provided evidence for
the potential benefits of stereoregularity, the authors only compared the mobility for highly
isotactic polymers with atactic polymers and thus were not able to target a clear structure-
function relationship. Further, the drift mobility reported is difficult to contextualize
relative to SCLC and OFET mobilities that are reported today.
35

Scheme 2.1. Synthesis of a) monomer 3, b) PCzEA polymer with different routes.
38

To address these issues and bring further insight to the role of tacticity in
influencing charge carrier mobility in NCPEPs, here we report the synthesis of PCzEA
samples with dyad isotacticity ranging from ~45 – 95% and we measure the µh using the
SCLC technique. We find that µh increases as dyad tacticity increases and ultimately
converges with the well-known conjugated polymer P3HT. As such, we report clear
evidence, for the first time, that increasing the isotacticity of NCPEPs can improve charge
transport and make them competitive with conjugated polymers.
2.2 Experimental
The synthetic route to the polymer samples is depicted in Scheme 2.1. Synthesis of
monomer 3 (Scheme 2.1), was achieved without any modification from a literature
procedure.
36
Monomer 3 was then polymerized via different radical and anionic
polymerization routes (Scheme 2.1 and Table 2.1) in order to target different levels of
isotacticity. Polymer 4a was synthesized by free radical polymerization using AIBN as the
initiator, leading to an atactic polymer (m = 45.5%). In order to target intermediate levels
of isotacticity, we focused on the use of Lewis acid additives to the standard free radical
polymerization, which have been used to generate isotactic polymers.
37
The first use of
Lewis acids to control tacticity in radical polymerization was reported by Okamoto et al,
38

who could achieve some degree of stereo-control in acrylamides using a catalytic amount
of Lewis acids such as Yb(OTf)3, Y(OTf)3, and Sc(OTf)3. The detailed mechanism was
first proposed by Kamigaito et al,
39
where the Lewis acid was thought to enforce a multi-
site coordination with the polar carbonyl functionality of the monomer, leading to the
preferential meso placement. Furthermore, it was shown by Biswajit et al,
40
that the degree
of isotacticity in acrylamides could be controlled by using a mixture of solvents in different
39

ratios along with catalytic amount of Lewis acids. Using this approach, polymers 4b-4e
were synthesized by radical polymerization in the presence of a catalytic amount of Lewis
acids (Y(OTf)3 was used for polymers 4b and 4c, while Sc(OTf)3 was used for polymers
4d and 4e) with a mixture of solvents (toluene and n-butanol). Based on the Lewis acid
used and the ratio of toluene to n-butanol, the dyad tacticity was tuned from m = 50.7 –
65.8%.
In order to target higher levels of isotacticity, anionic polymerization conditions
were employed. The use of anionic polymerization to achieve stereo-control has been
known since 1958.
41
The tacticity of the polymers formed by anionic polymerization can
be affected by different reaction conditions [effect of counterion, ratio of Lewis base
(diethyl ether or THF) to initiator, and temperature during polymerization] and was studied
by Fowells et al for acrylates and methacrylates.
42
Polymers 4f-4h were synthesized using
n-BuLi as the initiator in the absence of Lewis base in toluene at low temperature to achieve
highly isotactic polymer. In this case, the meso dyad content varied from 76.6 – 82.3%
based on the concentration of n-BuLi. Mechanistically, the Li
+
ion is chelated to the
terminal and penultimate carbonyl oxygens on the growing polymer chain in the absence
of a Lewis base, forcing the monomers to achieve meso placement. Isotacticity thus
increases as Li
+
ion concentration increases, as we see with polymers 4f-4h with 15-45%
n-BuLi. Polymer 4i was synthesized using a mixture of EtMgCl/Chalcone
(Benzalacetophenone) as initiator in the presence of Lewis base (diethyl ether) at 30
0
C to
achieve the highest isotactic content. The mechanism is similar to that of Li
+
ion
coordination and was previously reported by Uryu et al
43
and used for the synthesis of
highly isotactic PCzEA. Polymer 4i gave the highest isotacticity (m = 94.7).
40

2.3 Results and Discussion
The dyad and triad tacticity of the polymers were assessed via
1
H NMR and
13
C
NMR, respectively.
1
H and
13
C NMR of polymer 4i are shown in Figure 2.1 along with
the formula
44
used to calculate the tacticity of the polymers. In the
1
H NMR one can see
that in case of meso (m) -CH2 (Carbon 11), it gives two different peaks at 0.87ppm and
1.37ppm because the two protons are magnetically non-equivalent, while the racemic (r) -
CH2 (Carbon 11) protons are magnetically equivalent and hence give a single peak at
1.15ppm. The rest of the assignment of the peaks for
1
H NMR are given in Figure 2.1a.
For calculating triad tacticity -CH2 (Carbon 11)
13
C peaks were used in-place of the -CH
(Carbon 10)
13
C peak because the -CH (Carbon 10)
13
C peak overlapped with the -CH2
(Carbon 7)
13
C peak. The isotactic triad (mm)
13
C peak for -CH2 (Carbon 11) appears at
33.45 ppm, the heterotactic triad (mr/rm) around 34.3 ppm, and the syndiotactic triad (rr)
around 35.20 ppm, this also matches the 2D single bond correlation spectra, Heteronuclear
single quantum coherence (HSQC), as shown in the Appendix A, Figure A.4 and A.5.
The rest of the assignments of the
13
C peaks are given in Figure 2.1b. All the assignments
are consistent with previous literature with better resolution.
45

Here, we have used the Mott-Gurney SCLC technique to measure the hole
mobilities of the polymer thin films of PCzEA without and with annealing (Table 1 and
Figure 2). We see a gradual increase in the hole mobilities as the dyad tacticity increases
ranging from 2.11 x 10
-6
cm
2
V
-1
s
-1
for totally atactic polymer 4a to 4.68 x 10
-5
cm
2
V
-1
s
-1

for the highly isotactic polymer 4i when cast at room temperature without annealing.
41

Table 2.1 Reaction Conditions, Yield, Molecular Weights, Ð, Dyad and Triad isotacticty and SCLC mobilities for family of
isotactic PCzEA.
Polymer Condition
Yield
(%)
Solvent
Mn
(kDa)
a

Ð
Dyad
Tacticity
b

m / r %

Triad Tacticity
c

mm/ (mr/rm) / rr %
µh (cm
2
V
-1
s
-1
)
d,f

Non - Annealed

µh (cm
2
V
-1
s
-1
)
e,f
Annealed
4a 100
0
C / 7d 77 Toluene 27.5 3.6 45.5 / 54.5 - / - / - (2.11±0.35) x 10
-6
(1.69±0.89) x 10
-5

4b Y(OTf)3/ 100
0
C / 7d 62
Toluene/n-
Butanol
(1:3)
14.4 4.2 50.7 / 49.3 - / - / - (2.75±0.62) x 10
-6
(7.13±0.22) x 10
-6

4c Y(OTf)3/ 100
0
C / 7d 54
Toluene/n-
Butanol
(1:1)
15.3 3.9 53.8 / 46.2 - / - / - (2.86±0.53) x 10
-6
(1.10±1.1) x 10
-5

4d
Sc(OTf)3/ 100
0
C /
7d
58
Toluene/n-
Butanol
(1:3)
18.3 4.0 60.8 / 39.2 - / - / - (3.36±0.28) x 10
-6
(1.29±0.75) x 10
-5

4e
Sc(OTf)3/ 100
0
C /
7d
50
Toluene/n-
Butanol
(1:1)
21.4 3.6 65.8 / 34.2 - / - / - (3.60±0.52) x 10
-6
(1.56±0.53) x 10
-5

4f
15 mol% n-BuLi/
0
0
C / 1d
69 Toluene 7.4 3.5 76.6 / 23.4 64 / 33 / 3 (1.17±0.57) x 10
-5
(7.46±0.12) x 10
-5

4g
30 mol% n-BuLi/
0
0
C / 1d
63 Toluene 6.7 3.0 80.3 / 19.7 72 / 23 / 5 (2.04±0.77) x 10
-5
(1.00±0.22) x 10
-4

4h
45 mol% n-BuLi/
0
0
C / 1d
52 Toluene 5.5 3.2 82.3 / 17.7 76 / 16 / 8 (2.15±0.25) x 10
-5
(1.42±0.54) x 10
-4

4i
33 mol% EtMgCl/
30
0
C / 1d
75 Toluene 6.2 3.4 94.7 / 5.3 90 / 10 / 0 (4.68±1.03) x 10
-5
(2.74±0.78) x 10
-4

P3HT - - - - - - - (1.36±1.22) x 10
-4
(5.8±1.16) x 10
-4

P3HTT-
DPP
- - - - - - - (1.73±0.59) x 10
-4
(9.29±1.33) x 10
-4

a
Determined by SEC with polystyrene standards and o-DCB eluent.
b
Determined from
1
H NMR.
c
Determined from
13
C NMR, “
- “represents triad tacticity cannot be calculated because of peak overlap.
d
Measured from neat, as-cast polymer films.
e
Measured
from as-cast polymer films after 30min annealing at 150
0
C.
f
Data represents an average of at-least 12 pixels.
42

Figure 2.1. NMR spectra of ~95% dyad Isotacticity PCzEA (4i) a)
1
H NMR with formula
for dyad tacticity (peak at 1.28ppm is from grease) b)
13
C NMR with formula for triad
tacticity.
The hole mobility for the highly isotactic polymer is almost ~25 times higher than
the atactic polymer, which is a significant augmentation relative to the results of Uryu et
al.
34
which indicated only a 6-fold increase in hole mobility. Further, as seen in Table 2.1
and Figure 2.2, there is a clear trend of increasing hole mobility with increasing
isotacticity. This effect is accentuated with thermal annealing at 150
0
C for 30 minutes, as
clearly seen in Figure 2.2. Polymers 4a-4e (m = 45.5-65.8%) saw a relatively small
increase in hole mobility with annealing. Sample 4a was somewhat of an outlier in this
regard as it showed the highest mobility out of 4a-4e after annealing, likely due to the
higher molecular weight of the polymer.
46
However, for the highly isotactic polymers 4f-
4i, the mobilities increased more drastically and fully consistent with the trend in tacticity.
43

Specifically, polymer 4i (m=94.7%) saw an increase from 4.68 x 10
-5
cm
2
V
-1
s
-1
to 2.74 x
10
-4
cm
2
V
-1
s
-1
which is comparable to hole mobility of the well-known conjugated polymer
poly(3-hexylthiophene) (P3HT) as seen in Table 1. Along with annealing at 150
0
C, films
were also annealed at 105
0
C (~Tm of the polymers, Appendix A, Table A.3) and hole
mobilities were measured but gave similar results as unannealed ones (Appendix A, Table
A.2). More detailed investigation will be needed to understand the changes in morphology
induced by annealing, but it is possible that higher temperature annealing results in higher
degrees of crystallinity and increases π – π stacking. Of critical importance is the effect of
tacticity on hole mobility as seen most clearly with polymer 4i, giving a hole mobility of
2.74 x 10
-4
cm
2
V
-1
s
-1
with annealing which is comparable to annealed P3HT and the semi-
random conjugated polymer P3HTT-DPP
47
(Table 2.1) and higher than either unannealed
conjugated polymer. Hence one can indeed increase the charge carrier mobility of NCPEPs
and even match the charge carrier mobilities of CPs by increasing the isotacticity of the
NCPEPs.
While a clear correlation between tacticity and charge carrier mobility was
observed, thin film absorption properties were found to be invariant. The characteristic
carbazole π – π* transition at 295nm and carbazole n – π* transitions at 330nm and 344nm
(Appendix A, Figure A.6)
48
was observed in all cases, with an optical band gap of
3.45eV.
49
Similarly, the HOMO level of all polymers was found to be the same (5.83 -
5.85eV) as estimated from the onset of oxidation in the first cycle of cyclic voltammetry
(CV) on thin films.
44

Figure 2.2. Relationship of hole mobility of as cast and annealed films with the tacticity
of the polymers.
In contrast, the emission spectra of the polymers are observed to vary with tacticity.
Figure 2.3a illustrates the photoluminescence (PL) spectra of the unannealed polymer
samples. For comparison purposes, the polymers can be divided into three categories: low
isotacticity (45.5-65.8%) for 4a-4e, intermediate isotacticity (76.6-82.3%) for 4f-4h, and
high isotacticity (94.7%) for 4i. For the polymers with low isotacticity, while there is not
necessarily a clear trend, specific peaks can be identified at 350nm (0-0 transitions), 367nm
and 385-390nm (vibronic bands).
48
In general, these polymers have the strongest emission
and we can observe a red shifting of the most intense peak from 367nm with 4a towards
390nm with 4e. Additionally, with 4d and 4e the emergence of a peak at 405nm (4d) and
~420nm (4e) is evidence of an excimer-type peak likely associated with increasing π-
stacking in the more isotactic polymer.
50,51
For the polymers with intermediate isotacticity
(4f-4h), a less intense emission is observed with sharper peaks corresponding more likely
to excimer emission at 405nm and 430nm.
48
Finally, the most isotactic sample 4i shows a
45

dramatically decreased PL intensity, likely due to increased π-stacking driven aggregation.
For the annealed films (Figure 2.3b), minimal change is observed in the intermediate and
high tacticity polymers (4f-4i) and little change in spectral shape is observed for polymers
4a-4h, despite enhancement in PL intensity for 4b and 4c. Overall, the shift toward better
defined excimer peaks and enhanced quenching with increasing isotacticity is good
evidence that π-stacking is enhanced with greater stereoregularity.

Figure 2.3. Emission profile of the family of PCzEA films a) unannealed b) annealed at
150
0
C for 30mins.
46

To study the morphology, the films were further analyzed by thin film X-ray
diffraction (GIXRD), however no peaks were obtained from the non-annealed films. A
primary peak at 2 θ of ~0.5
0
was observed for films annealed at 150
0
C for 30min, which
indicated formation of some kind of ordered structure or higher order crystallite domains
with very large d-spacing
52,53
of about ~16-19nm and crystallite size of ~30-38nm
(Appendix A, Table A.1) with no other peaks observed (Appendix A, figure A.7). To get
the actual lamellar spacing and π – π stacking distance, further studies will be required with
higher resolution Grazing Incidence wide angle X-ray Scattering (GIWAXS).
2.4 Conclusions
Here we have reported the first clear experimental evidence that control of side
chain tacticity in NCPEPs can improve charge carrier mobility. Specifically, as the
isotacticity of PCzEA is increased from m= 45.5% to 94.7%, the hole mobility is observed
to increase by a factor of ~25 in unannealed films in a regular, monotonic fashion. It is
found that annealing accentuated the increase in hole mobility with increasing isotacticity,
culminating in a µh of 2.74 x 10
-4
cm
2
V
-1
s
-1
, which is comparable to that of fully conjugated
polymers used in state-of-the-art OPV. Considering potential advantages of NCPEPs over
CPs, including stability, mechanical properties, and synthetic flexibility (i.e.
controlled/living polymerization methods), these results suggest a potential route toward
high performance polymers for electronic applications. Future work includes more detailed
morphological investigation of the polymers, further investigation of structure-function
relationships (including molecular weight dependence), and evaluation in organic
electronic devices.
47

2.5 References
(1) Lu, L.; Zheng, T.; Wu, Q.; Schneider, A. M.; Zhao, D.; Yu, L. Recent Advances in
Bulk Heterojunction Polymer Solar Cells. Chem. Rev. 2015, 115 (23), 12666–12731.
(2) Holliday, S.; Li, Y .; Luscombe, C. K. Recent Advances in High Performance Donor-
Acceptor Polymers for Organic Photovoltaics. Prog. Polym. Sci. 2017, 70, 34–51.
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55

Chapter 3: Influence of Alkyl Chain Spacer Length on the Charge Carrier Mobility
of Isotactic Poly (N-carbazolylalkyl acrylates)

3.1 Introduction
Conjugated polymers (CPs) are appealing for many electronic applications,
1,2

including organic light emitting diodes (OLEDs),
3
organic photovoltaics (OPVs),
4
organic
field effect transistors (OFETs),
5
batteries,
6
and bioelectronics
7
due to their optical,
semiconducting, biocompatibility and electrochemical properties. CPs also have numerous
advantages over inorganic analogues such as lightweight, low-cost, flexibility, low toxicity
and compatibility with roll-to-roll processing.
8
In recent years optimized polymers have
led to high performance devices.
9–12

However, CPs do suffer from several deficiencies including poor environmental
stability,
13
limited mechanical properties,
14
low molecular weights,
15
and limited synthetic
methodologies to achieve advanced architectures. While there have been advancements
towards achieving CPs with controlled polymerizations;
16
it is still challenging to
synthesize polymers with narrow dispersity (Đ), high molecular weight, and control over
end groups.
17,18,19,20

Non-conjugated electroactive polymers have garnered interest over the years due
to the limitations of CPs.
21,22
Studies have shown that non-conjugated polymers containing
electroactive pendant groups, also called non-conjugated pendant electroactive polymers
(NCPEPs), possess enormous potential. In analogy to side chain liquid crystal polymers
(SCLCPs),
23,24
it is expected that the properties of these polymers will be strongly
56

influenced by the structure of the main chain, pendant group, spacer chain, and
stereoregularity (Figure 3.1).
25,26
NCPEPs are attractive because of their easy pendant
modification, high achievable molecular weights, diversity in accessible synthetic
methodologies and the potential for precise control over hierarchical assemblies enabled
by advanced architectures. Due to these strengths, they have been explored for use in
organic electronics, notably in the work of Thelakkat.
27–29

Figure 3.1. Structure of the NCPEP poly(2-N-carbazolylethyl acrylate (PCzEA) indicating
the structural variables (left) and an isotactic polymer PCzEA (right).

NCPEPs are also of potential interest in flexible electronics due to analogy with
insulating polymers (e.g., HDPE) that have been demonstrated to improve mechanical
properties in polymer and polymer/fullerene blends.
30,31
Despite such potential advantages,
NCPEPs are generally reported to have charge carrier mobilities several orders of
magnitude lower than CPs.
32

Inspired by Uryu et al.,
33
who showed that highly isotactic poly(2-N-carbazoylethyl
acrylate) (PCzEA) (Figure 1) had a hole mobility (µh) six times higher than the atactic
57

counterpart and the theoretical proposition of improvement in µh with increased backbone
stereoregularity of poly(N-vinylcarbazole) (PVK);
34,35
we have recently shown clear
evidence of the monotonic increase in µh with increasing isotacticity in PCzEA. We found
that µh increased from 2.11 x 10
-6
cm
2
V
-1
s
-1
to 4.68 x 10
-5
cm
2
V
-1
s
-1
in unannealed
samples as the dyad isotacticity increased from ~45% to ~95%, and µh is enhanced to 2.74
x 10
-4
cm
2
V
-1
s
-1
with thermal annealing of the 95% isotactic sample, rivalling poly(3-
hexylthiophene) (P3HT).
36
Later work has shown that µh was increased with tacticity for
PVK.
37

However, there are several structural variables that can potentially influence µh,
including the main chain, pendant group, spacer, and stereoregularity,
38,39
and
understanding the structure-function relationships is essential for designing higher
performing polymers. In our previous report on PCzEA, the alkyl spacer was kept constant
at two carbons and only the effect of stereoregularity on µh was studied. Here we
investigate for the first time the role of spacer length on charge-carrier mobility in
stereoregular electroactive pendant polymers.
Hence, we report the synthesis of a family of poly(N-carbazoylalkyl acrylate)
(PCzXA) polymers with different even number alkyl spacers ranging from two to twelve
carbons. We investigate these spacers on two different isotactic PCzXAs of ~75% and
~87% dyad isotacticity. We find that as the spacer length increases from two carbons to
either four or six carbons, the µh increases. With spacers longer than six carbons, the effect
of the isotacticity is diminished as the degrees of freedom are increased and the µh
decreases.
58

Although odd-even effects have been observed for thermal and physical properties
with SCLCPs
24,40
we have limited our work to even spacers. In our previous work we used
direct polymerization of N-carbazoylethyl acrylate and found that anionic polymerization
gave the highest isotacticity. Anionic polymerization was preferred as it gives high
stereocontrol under living polymerization conditions, which is important for extension to
advanced architectures.
41
However anionic polymerization can pose a limitation due to
functional group tolerance. Hence, here we explored post-polymerization functionalization
with transesterification of acrylates, which has been shown to be quantitative under several
conditions.
42–44
Another advantage of post-polymerization functionalization is that it
allows an “apples-to-apples” comparison as one can examine a structural variable on
otherwise identical backbones.
We did however attempt the direct polymerization route. The direct synthetic route
is depicted in Appendix B, Scheme B.1. Synthesis of the 2-C acrylate, was achieved
according to the literature.
45
Monomers with four, six and eight carbon spacers were also
synthesized. Monomers were polymerized using n-BuLi in toluene. While the polymers
gave reasonable dyad isotacticities of ~80%, the molecular weights were low, ranging from
6.2 kg/mol to 2.8 kg/mol (Appendix B, Table B.1). The observation of decreasing
molecular weight as the spacer length increased is conjectured to be due to intramolecular
interaction between the aromatic ring and the lithium counterion coordinated with the
acrylate, which hinders chain propagation.

59

3.2 Experimental
To target higher molecular weights and to have a more accurate comparison of
spacer length, we moved to post-polymerization functionalization (Scheme 1), specifically
taking inspiration from the transesterification of poly(methyl acrylate) (PMA) using
ZnTac24 as catalyst.
42
Synthesis of 2 was achieved according to the literature.
46

Compounds 7b-7f, were synthesized based on a literature procedure.
47
PMA was
synthesized at two different levels of isotacticity. Polymer 9a was synthesized using n-
BuLi in toluene at -20 C,
48
yielding dyad tacticity of 74.3% with an Mn of 33.4 kg/mol.
Polymer 9b was synthesized using PhMgBr in toluene at 0 C
48
resulting in 86.7% dyad
tacticity with an Mn of 13.5 kg/mol. The polymers were synthesized using standard
Schlenk techniques and extraordinary measures commensurate with rigorous anionic
polymerization were not applied for this model structure-function study as is consistent
with the dispersities of 1.5 and 2.0. The difference in dyad isotacticity is due to stronger
coordination of Mg
+
with the terminal and penultimate carbonyl oxygens as compared to
Li
+
, enforcing a higher percentage of meso placement.
49

Polymers 9a and 9b were subjected to transesterification with compounds 2 and
7b-f using ZnTac24.
50
Polymers 10a-15a were derived from the lower tacticity 9a, and
polymers 10b-15b were derived from the higher tacticity 9b. All transesterifications
proceeded with high conversions of >97%, as calculated from
1
H NMR (Table 1). The
lower tacticity polymers 10a-15a were soluble in chloroform at 10 mg/ml and the solubility
increased as the spacer length increased. The higher tacticity polymers 10b-15b were only
soluble after stirring at 60

C in chloroform at 10 mg/ml with solubility also increasing as
the spacer length increased. This method of post-polymerization functionalization
60

promises a method to make new NCPEPs which would otherwise be inaccessible via direct
anionic polymerization.

Scheme 3.1 Synthesis of monomers, PMA polymers, and PCzXA polymers
3.3 Results and Discussion
We used the space charge limited current (SCLC) technique to measure the hole
mobilities of polymer thin films with and without annealing (Table 3.1 and Figure 3.2).
All the polymers were dissolved in chloroform, and then spin coated to yield films of
thickness of 55nm - 65nm.
61

Table 3.1 Polymer Yields/Conversions, Molecular Weights, Ð, Dyad Isotacticity and SCLC mobilities for family of isotactic
PCzXA polymers with different alkyl chain spacers.
Polymer
Carbon
Spacer
Yield
a
/Conversion
b

(%)
Mn
(kg/mol)
Ð Dyad Tacticity
e

µh (cm
2
V
-1
s
-1
)
f,h

Non - Annealed
µh (cm
2
V
-1
s
-1
)
g,h
Annealed
9a - 40
a
33.4
c
1.5 74.3 - -
9b - 45
a
13.5
c
2.0 86.7 - -
10a 2 99
b
24.9
d
2.4 74.3 (3.0±0.22)x10
-5
(5.5±0.39)x10
-5

11a 4 98
b
26.4
d
2.8 74.3 (4.2±0.74)x10
-5
(7.2±0.27)x10
-5

12a 6 97
b
27.2
d
2.7 74.3 (2.9±0.45)x10
-5
(3.5±0.15)x10
-5

13a 8 98
b
29.6
d
2.4 74.3 (8.9±0.40)x10
-6
(1.4±0.09)x10
-5

14a 10 99
b
31.7
d
2.8 74.3 (5.5±0.18)x10
-6
(1.1±0.53)x10
-5

15a 12 98
b
32.3
d
2.1 74.3 (2.7±0.62)x10
-6
(9.1±0.57)x10
-6

10b 2 99
b
21.4
d
3.0 86.7 (4.5±0.41)x10
-5
(1.1±0.14)x10
-4

11b 4 97
b
22.7
d
2.7 86.7 (6.2±0.29)x10
-5
(1.5±0.35)x10
-4

12b 6 98
b
24.3
d
2.6 86.7 (7.4±0.44)x10
-5
(2.0±0.27)x10
-4

13b 8 98
b
27.0
d
2.2 86.7 (9.0±0.77)x10
-6
(9.7±0.62)x10
-5

14b 10 99
b
27.8
d
2.9 86.7 (5.2±0.35)x10
-6
(8.8±1.10)x10
-5

15b 12 98
b
29.3
d
2.4 86.7 (4.7±0.53)x10
-6
(7.5±0.47)x10
-5

a
Polymerization yield,
b
Transesterification conversion, determined by
1
H NMR.
c
Determined by SEC with polystyrene standards
and THF eluent.
d
Determined by SEC with polystyrene standards and o-DCB eluent.
e
Determined from
1
H NMR.
f
Measured
from neat, as-cast polymer films.
g
Measured from polymer films after 30min annealing at 150

C.
h
Data represents an average of
at-least 12 pixels.
62

For the unannealed polymers with isotacticity of ~75% (10a-15a), as the spacer
length increased from two carbons to four carbons, the µh increased from 3.0 x 10
-5
cm
2
V
-
1
s
-1
(10a) to 4.2 x 10
-5
cm
2
V
-1
s
-1
(11a) and then gradually decreased with longer spacers
to 2.7 x 10
-6
cm
2
V
-1
s
-1
for the twelve-carbon spacer (15a). Even though the µh decreases
after four carbons, there is little change cross the longer spacers (8-12 carbons). The effect
of alkyl spacer length was similar for the unannealed polymers with ~87% isotacticity
(10b-15b). However, in this case, the µh peaks with the six-carbon spacer. Hence the µh
increases from 4.5 x 10
-5
cm
2
V
-1
s
-1
for the two-carbon spacer (10b) to 7.4 x 10
-5
cm
2
V
-1

s
-1
for six-carbon spacer (12b) and then sharply drops to 9 x 10
-6
cm
2
V
-1
s
-1
for the eight-
carbon spacer (13b) and gradually decreases thereafter. Based on the results of the
unannealed films, the optimal spacer length for high µh is based on the degree of
isotacticity, which show that the influence of isotacticity and spacer length are not
independent.
Similar trends were observed for the annealed films but with higher values for µh.
The annealing conditions were not optimized and our previously reported conditions for
PCzEA of 150

C for 30 mins were used. With the 75% isotactic polymers, the trend was
the same before and after annealing, but the annealed samples with two and four-carbon
spacers showed slightly higher mobilities. For spacer lengths of six to twelve carbons there
was almost no change induced by annealing.
63

Figure 3.2. Relationship of hole mobility of as cast and annealed films for the polymers
with different spacer chain lengths.

For the 87% isotactic polymers, annealing did not change the trend, but did result
in dramatic increases in mobility for all samples. Specifically, a µh of 1.1 x 10
-4
cm
2
V
-1
s
-
1
was measured for the two-carbon spacer (10b), which increased to 2 x 10
-4
cm
2
V
-1
s
-1
for
six carbons (12b) (competitive with most conjugated polymers known in literature
51
) and
then sharply drops down to 9.7 x 10
-5
cm
2
V
-1
s
-1
for the eight-carbon spacer (13b) and
further gradually decreases. Even though µh of the annealed six-carbon spacer (12b)
reached 2.0 x 10
-4
cm
2
V
-1
s
-1
, it still falls short of our previously reported µh for the
annealed ~95% isotactic PCzEA, which suggests that even higher µh can be achieved with
higher control over tacticity.
To gain insight into the mobility-spacer length-tacticity relationship we sought to
look beyond primary structure correlations. As a first step we investigated thin film UV-
64

Vis absorption which was found to be mostly invariant but we observed a slight blue shift
(Appendix B) in the case of the two-carbon spacer for both levels of tacticity indicating
the possibility of H-aggregation with the two-carbon spacer.
52
For all films characteristic
carbazole - * transitions (~295 nm) and n- * transitions (~330 nm and 344 nm) were
observed. Similarly, the HOMO levels of all the polymers were found to be the same as
measured by cyclic voltammetry (5.82 - 5.86 eV).
Photoluminescence (PL) spectra yielded some structural insight (Appendix B). In
general, 0-0 transitions were observed at 350 nm with another vibronic band at 368 nm.
Sharper peaks were observed from 405 to 430 nm corresponding to excimer emission,
which is diagnostic of -stacking.
53
For the 75% isotactic polymers (10a-15a), with spacers
longer than four carbons, the excimer emission peaks are no longer prominent. A similar
trend is also observed for the 87% isotactic polymers (10b-15b), where with spacers longer
than eight carbons, the excimer peaks are not as sharp. It can be inferred that with polymers
of lower isotacticity, -stacking is more favorable only at shorter spacer lengths. This
corresponds well with the hole mobility data. With higher isotacticity, -stacking remains
favorable to longer spacer lengths, which is again consistent with the mobility data.
To study the morphology more directly, thin films were further analyzed by grazing
incidence X-ray diffraction (GIXRD); however, no peaks were observed for any of the
films, in agreement with what we had seen previously with PCzEA. The results from
GIXRD are also consistent with DSC where no prominent peaks were observed for any
samples (Appendix B). As such, these polymers appear to be largely amorphous and it is
difficult to gain deep insight into the bulk structure and -stacking.
65

Figure 3.3 DFT optimized structures of atactic PCzEA and isotactic PCzEA (with inset showing helical backbone) (top) and isotactic
polymer chains of PCzXA with increasing spacer chain length (bottom). The polymer backbones are highlighted and all polymers have
40 repeat units.
66

We therefore elected to turn to simulations to model chain and bulk structure. A
database of atactic and fully isotactic PCzXA chains with 20 and 40 monomers for each
spacer length was generated. These chains were optimized using B3LYP/6-31+G(d) in Q-
Chem 5.0.
54
From the DFT optimized structures (Figure 3.3) with 40 repeating units, there
is clearly a significant difference between the atactic and isotactic structures. Where the
atactic structure is more randomized and clumped, the isotactic structures are elongated
with all the pendant units surrounding the helical backbone. As the spacer is increased from
two to twelve carbons for the isotactic polymers, the orientation of pendant units becomes
more disorganized and tends toward -stacked dimers even though the backbone remains
helical. This type of helical structure is seen in many isotactic polymers.
55,56
Looking down
the axis of the polymer chains, we see that the carbazoles are nicely oriented around the
backbone with the four-carbon and six-carbon spacers, as opposed to the two-carbon
spacer, which is more compact and slightly puckered. As the spacer length increases from
eight carbons to twelve carbons, the favorable orientation is deviated and the pendant
groups are more randomly organized.
To understand the effect of annealing and how the polymers pack in a thin film, we
turned to MD simulations (Figure 3.4). The initial topology files for 20 monomer chains
(MD calculations used 20 monomers because of computational limitations) were obtained
from Automated Topology Builder (ATB) and Repository (Version 3.0).
57
Chains of each
polymer were permitted to relax for 1ns in isolation at 300K (using the LAMMPS suite),
according to the intramolecular components of the GROMOS_54A7 force field, thus
mimicking their arrangement in solution. A total of 64 relaxed chains for each polymer
were placed in a bounded simulation box at periodic positions and orientations, with
67

sufficient space between chains to avoid interchain interactions. This simulation volume
was then compressed over a period of 40 ps at 300K until the density reached an average
of 1.2 g/ml (density of PVK)
58
, mimicking the effect of solvent evaporation. The
morphologies were simulated with varying temperature from 300K to 425K for 4ns. The
annealed films were finally cooled down to room temperature over a further 4ns period,
before equilibrating at 300K for a final of 4ns. Figure 3.4a illustrates the case of the six-
carbon spacer (detailed calculation steps for all spacers are in the Appendix B).

Figure 3.4 a) MD simulations of 64 chains of PCzHA (six-carbon spacer) packed into a
thin film configuration after annealing. b) The stacking of different carbazole units from
multiple chains showing short range ordering (blue labelling).
From these MD simulations, it was observed that as the films were annealed, the
interactions between chains increases significantly. Upon mapping the carbazole moieties,
we see an enhanced -  stacked short range ordering between multiple chains (Figure
3.4b) and the highest interchain -  stacking is observed for the six-carbon spacer. These
simulated results with 100% isotactic polymer help to explain why the 87% isotactic
polymer shows the highest mobility with a six-carbon spacer. However, the 75% isotactic
68

polymer shows the highest mobility with the four-carbon spacer. We propose that as the
polymer becomes more atactic, that extended interchain interactions (to form continuous
pi-stacked pathways) become less favorable in the more disordered system and intrachain
interactions become more important to the overall mobility. We observe in the DFT models
that the degree of intrachain ordering of the carbazole units increases as the spacer length
decreases. As such, isotactic sequences based on shorter spacers are expected to give rise
to more local (intrachain) ordering and dominate the mobility. We notice that there is little
difference between the mobility for the 2 and 4 carbon spacers in the case of the 75%
isotactic sample (with and without annealing). We postulate that the 4-carbon spacer leads
to a somewhat higher mobility than the 2-carbon spacer due to slightly enhanced
intermolecular interactions that are favored with the longer spacer.
3.4 Conclusion
Here we have reported the effect of spacer lengths in NCPEPs on the charge carrier
mobility in stereoregular polymers. Specifically, the hole mobility was observed to increase
as the spacer length increases from two carbons to four carbons for the 75% isotactic
polymer and up to a six-carbon spacer for the 87% isotactic polymer. With further increase
in the spacer length, the hole mobility decreases rapidly and the effect of tacticity is
diminished. It is found that this increase in hole mobility is likely due to a helical
orientation in the isotactic polymers which increases the short range -  stacked ordering
in the thin films, especially with annealing, as simulated via DFT and MD. Considering
the potential advantages of NCPEPs over CPs, these results show that NCPEPs can be
designed to rival the mobility of conjugated polymers by tuning not only degree of
isotacticity, but also the spacer length.
69

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79

Chapter 4: Contrasting the Charge Carrier Mobility of Isotactic, Syndiotactic, and
Atactic Poly((N-carbazolylethylthio)propyl methacrylate)

4.1 Introduction
With the development of novel manufacturing technologies, conjugated polymers
(CP) are emerging as viable materials for many optoelectronic applications, such as organic
photovoltaics (OPVs),
1–3
organic field-effect transistors (OFETs),
4,5
organic light-emitting
diodes (OLEDs),
6,7
batteries,
8–10
and bioelectronics
11,12
due to their numerous advantages
over inorganic analogs. Among various benefits of CPs such as lightweight, low cost, low
toxicity, and easy processibility, the high charge carrier mobilities of CPs plays a crucial
role in the fabrication of high-performance devices such as OPVs and OFETs.
13

Despite outstanding performance in optoelectronic applications, CPs nonetheless
are limited by several challenges.
14
While approaches have recently been developed to
overcome some of these challenges;
15–17
notably, CPs still lack effective synthetic methods
to make narrow dispersity and high molecular weight polymers, which are crucial for the
fabrication of efficient optoelectronic devices
18
and the development of advanced
architectures such as block copolymers.
19,20
Poor environmental stability and restricted
mechanical properties are also limitations of CPs.
21,22

Recently non-conjugated electroactive polymers have been explored in many fields
as an alternative for CPs.
23,24
Specifically, non-conjugated pendant electroactive polymers
(NCPEPs), which are non-conjugated polymers containing electroactive units in the side
chain, possess enormous potential. Such polymers offer access to the broad range of
controlled polymerization techniques of non-conjugated polymers that promise access to
80

highly tailored structures with diverse architectures.
25
With NCPEPs, in analogy to side-
chain liquid crystal polymers,
26,27
optoelectronic properties are strongly influenced by the
structure of the polymer backbone, pendant group, spacer (length and identity), and
stereoregularity (Figure 4.1).

Figure 4.1 Structural features impacting properties in NCPEPs: Backbone structure, spacer
length, pendant group and stereoregularity.

In our recent study, we demonstrated the impact of isotacticity relative to atactic
polymers, where we found that hole mobility (µh) of NCPEPs increases proportionally to
the increasing isotacticity, achieving µh ~100 times higher than atactic analogs.
28
We
further showed the effect of the spacer length on the µh of NCPEPs, where we found that a
81

six carbon alkyl spacer is the optimum flexible spacer length to achieve high µh in isotactic
NCPEPs using highly isotactic poly(N-carbazolylalkyl acrylates) as our model system.
29

Although NCPEPs promise to overcome limitations of CPs, and examples
exhibiting higher charge carrier mobilities than CPs have been reported,
30,31
NCPEPs are
generally found to have charge carrier mobilities several orders of magnitude lower than
CPs.
32
Taking inspiration from the work of Uryu et al.,
33
who showed that highly isotactic
(m = ~97%) poly(2-N-carbazolylethyl acrylate) (PCzEA) had a µh of 1.7 x 10
-5
cm
2
V
-1
s
-
1
; being six times higher than the atactic counterpart, we have recently showed clear
evidence for the correlation of stereoregularity in PCzEA and µh. We found that µh
increased from 2.11 x 10
-6
cm
2
V
-1
s
-1
to 4.68 x 10
-5
cm
2
V
-1
s
-1
in unannealed samples as
the dyad isotacticity increased from m = ~45% to m = ~95%, and the µh is further increased
to 2.74 x 10
-4
cm
2
V
-1
s
-1
with thermal annealing of the ~95% isotactic sample, which is as
par with most of the well-known CPs such as poly(3-hexylthiophene) (P3HT).
34

However, our study of the effect of stereoregularity on the µh of NCPEPs was
limited to isotactic PCzEA, and further work done by Ozaki et al.,
35
on poly(N-
vinylcarbazole) (PVK), was also limited to the isotactic polymer. For designing optimized
NCPEPs proper understanding of the structure-function relationships is required. As such,
here we further investigate the effect of stereoregularity on the µh of NCPEPs by comparing
isotactic, syndiotactic and atactic polymers, keeping the pendant group, spacer length, and
polymer backbone constant.
We report a novel methodology for synthesis of a family of poly((N-
carbazolylethylthio)propyl methacrylate) (PCzETPMA) polymers with different tacticity
including isotactic PCzETPMA (mm = ~85%), syndiotactic PCzETPMA (rr = ~80%) with
82

two different molecular weights, and an atactic PCzETPMA. Using the previously
determined optimal spacer length of six atoms,
29
we find that both isotactic and atactic
PCzETPMA give comparable results to our previously reported isotactic and atactic
NCPEPs. Interestingly the low molecular weight syndiotactic PCzETPMA gave similar µh
to the atactic counterpart while the high molecular weight syndiotactic PCzETPMA gave
comparable µh to the isotactic counterpart. However, higher temperature annealing of the
high molecular weight syndiotactic polymer resulted in µh ten times higher than isotactic
PCzETPMA.
Consistent with our observation for acrylate polymers, anionic polymerization gave
the best control over tacticity, and hence anionic polymerization was preferred for this
study. To avoid the limitations of anionic polymerization, we used a post-polymerization
route using the thiol-ene reaction, which has been broadly used for post-polymerization
functionalization.
36,37
We used allyl methacrylate which has proven effective in yielding
both isotactic and syndiotactic polymers via anionic polymerization
38,39
and the allyl group
is amenable to post-polymerization functionalization.
40,41

4.2 Experimental
N-carbazolylethanethiol chosen as the electroactive pendant for the thiol-ene
reaction as to achieve the optimized spacer length and have the same pendant unit as our
previous studies.
28,29
Synthesis of N-carbazolylethanethiol (4) is depicted in Scheme 4.1a.
To achieve the desired polymers (6 – 9), allyl methacrylate was polymerized under
different conditions as depicted in Scheme 4.1b, with molecular weight and tacticity data
shown in Table 4.1. To synthesize the isotactic polymer (6), allyl methacrylate was reacted
using freshly prepared diphenylhexyllithium (DPHL) as the initiator in toluene, while
83

syndiotactic polymers (7 and 8) were obtained using DPHL as the initiator but using THF
as solvent. Similar approaches for allyl methacrylate were reported in the literature.
39
The
difference in stereoregularity using different solvents is based on solvation of the lithium
cation. In the case of toluene, the lithium cation is not solvated and hence binds with the
terminal and penultimate carbonyl oxygens yielding an isotactic polymer,
43
while in the
case of THF, the lithium cations are fully solvated and hence cannot bind carbonyl oxygens
giving syndiotactic polymer.
44,45
Finally to achieve the atactic polymer (9), we chose
reversible addition-fragmentation chain-transfer (RAFT) polymerization since it yielded a
reproducible level of tacticty.
46
Triad and pentad tacticity for all the polymers were
calculated from
1
H and
13
C NMR respectively (Table 1 and Supporting information) and
are referenced from PMMA NMR peak shifts.
47
Under the described conditions atactic (9)
(rr = ~50%), isotactic (6) (mm = ~85%), and syndiotactic (8) (rr = ~80%) PAMA samples
were achieved with Mn values of 12.6, 36.4, and 24.9 kg/mol, respectively. Increasing the
monomer concentration from 5 mmol to 10 mmol led to a significant increase in Mn with
anionic polymerization in THF to give polymer 7 (rr = ~80%) of 77.3 kg/mol. The effect
of monomer concentration on the molecular weight of the PMMA is well studied showning
similar results in the literature.
38
High molecular weight isotactic and atactic polymers were
not targeted because of the lower solubility in these cases.

84

Scheme 4.1 Synthesis of (a) Pendant group, (b) PAMA polymers, and (c) PCzETPMA
polymers.

Polymers 6 – 9 were then subjected to a photochemical thiol-ene reaction with
compound 4, using 2,2-dimethoxy-2-phenylacetophenone (DMPA) as photoinitiator and a
300nm LED as light source. The photochemical thiol-ene route gave >99% conversion and
was highly selective for the anti-Markonikov product as compared to other reported
reaction conditions.
48
Synthesis of polymers 6a – 9a is depicted in Scheme 4.1a, and the
method is adapted from literature with slight variation.
49
This thiol-ene post-
polymerization functionalization technique gives us a pathway to achieve new functional
NCPEPs with suitable tacticity and molecular weights with minimal to no defects. Both
syndiotactic polymers (7a – 8a) are readily soluble in chloroform up to 50 mg/ml at room
temperature. In contrast, the atactic (9a) and the isotactic polymers (6a) were only soluble
at 60

C in chloroform at 10 mg/ml.
85

Table 4.1 Polymer Yields/Conversions, Molecular Weights, Ð, Triad and pentad tacticity and SCLC mobilities for the family of
PCzETPMA polymers.
Polymer
Yield
a
/
Conversion
b

(%)
Mn
(kg/mol)
c

Ð
Triad
Tacticity
d
(%)
Pentad
Tacticity
e
(%)
µh (cm
2
V
-1
s
-1
)
f,j

Unannealed
µh (cm
2
V
-1
s
-1
)
g,j

Annealed at
120

C
µh (cm
2
V
-1
s
-1
)
h,j

Annealed at
150

C
µh (cm
2
V
-1
s
-1
)
i,j
Annealed at
210

C
6 75
a
36.4 1.4 85 (mm) 80 (mmmm) - - - -
7 90
a
77.3 1.2 80 (rr) 70 (rrrr) - - - -
8 85
a
24.9 1.4 80 (rr) 70 (rrrr) - - - -
9 55
a
12.6 1.4 50 (rr) 50 (rrrr) - - - -
6a >99
b
46.5 2.3 85 (mm) 80 (mmmm) (6.0±0.75)x10
-5
(2.19±0.22)x10
-4
(1.6±0.95)x10
-4
(1.47±0.55)x10
-4

7a >99
b
122.1 1.2 80 (rr) 70 (rrrr) (2.1±0.60)x10
-6
(1.1±0.28)x10
-4
(1.37±0.52)x10
-6
(1.82±0.48)x10
-3

8a >99
b
49.4 1.5 80 (rr) 70 (rrrr) (2.59±0.34)x10
-7
(2.23±0.41)x10
-8
(3.22±0.66)x10
-8
(9.81±1.1)x10
-7

9a >99
b
26.1 1.6 50 (rr) 50 (rrrr) (1.17±0.62)x10
-7
(4.03±0.44)x10
-8
(3.79±0.32)x10
-8
(4.37±0.70)x10
-7

a
Polymerization yield,
b
Thiol-ene conversion, determined by
1
H NMR.
c
Determined by SEC with polystyrene standards and
TCB eluent.
d
Determined from
1
H NMR.
e
Determined from
13
C NMR.
f
Measured from neat, as-cast polymer films.
g
Measured from
polymer films after 30 min annealing at 120

C.
h
Measured from polymer films after 30 min annealing at 150

C.
i
Measured from polymer
films after 30 min annealing at 210

C.
j
Data represents an average of at-least 20 pixels.
86

4.3 Results and Discussion
The space charge limited current (SCLC) technique was used to measure the µh of
polymer thin films with and without annealing (Table 4.1 and Figure 4.2). The annealing
temperatures were not extensively optimized and annealing above 210

C was avoided as
the atactic polymer (9a) started to lose more than 5 % of mass above 220

C as observed
in TGA (supporting information). All the polymers were spin-coated from CHCL3 to yield
films of thickness of 50 – 65 nm. For the atactic polymer 9a, annealed and unannealed
samples showed µh in the range of 10
-7
–10
-8
cm
2
V
-1
s
-1
. For the isotactic polymer 6a, the
unannealed sample gave µh of 6.0 x 10
-5
cm
2
V
-1
s
-1
which increased to 2.19 x 10
-4
cm
2
V
-
1
s
-1
when the film is annealed at 120

C for 30 mins. On further annealing to higher
temperatures, µh decreases to 1.47 x 10
-4
cm
2
V
-1
s
-1
when annealed at 210

C for 30 mins.
The µh at the 120

C annealing condition is on par with the unannealed µh of well-known
conjugated polymer poly(3-hexylthiophene) (P3HT)
50
and is similar to our previous studies
confirming that high µh can be achieved with isotactic NCPEPs.
Interestingly the two syndiotactic polymers gave significantly different results. For
the low molecular weight syndiotactic polymer 8a, unannealed films gave µh of 2.59 x 10
-
7
cm
2
V
-1
s
-1
, which is two orders of magnitude lower than unannealed isotactic polymer
6a and nearly identical with the unannealed atactic polymer 9a. On annealing of 8a, µh
decreased to 2.23 x 10
-8
cm
2
V
-1
s
-1
when annealed at 120

C for 30 mins and then increased
to a maximum 9.81 x 10
-7
cm
2
V
-1
s
-1
on further annealing at 210

C for 30 mins showing
a similar trend to the atactic polymer (Figure 4.2). For the low molecular weight
syndiotactic polymer 8a, even after annealing µh is still two orders of magnitude lower than
87

its isotactic counterpart which has comparable molecular weight (49.4 and 46.5 kg/mol,
respectively).

Figure 4.2 Effect of annealing on the hole mobility of PCzETPMA polymers with different
tacticity.
In contrast, the high molecular weight syndiotactic polymer 7a, even the
unannealed sample gave µh of 2.1 x 10
-6
cm
2
V
-1
s
-1
. The µh of polymer 7a is observed to
increase rapidly to 1.37 x 10
-4
cm
2
V
-1
s
-1
upon annealing at 120

C for 30 mins and further
increases to 1.82 x 10
-3
cm
2
V
-1
s
-1
upon annealing at 210

C for 30 mins surpassing
annealed P3HT and isotactic polymer 6a by an order of magnitude. This result is
unprecedented and shows a clear effect of molecular weight on the µh of the syndiotactic
polymer.
For further comprehension of the mobility – tacticity relationships, we investigated
several characterization techniques. First, we measured thin film UV–vis absorption, where
we saw little to no difference between all the polymers 6a – 9a for both annealed and
88

unannealed samples (Appendix C). For all films, characteristic carbazole π – π* transitions
(~295 nm) and n – π* transitions (~330 and 344 nm) were observed. The HOMO levels of
all the polymer were also found to be similar as measured by cyclic voltammetry (CV)
showing no effect of tacticity (5.62 – 5.69 eV) (Appendix C). The above-mentioned
HOMO value is 0.2 eV higher than previously reported PCzXA values as in this case the
HOMO is delocalized to the nearby S atom (Figure 4.3a).
In contrast to UV–vis absorption and cyclic voltammetry, Photoluminescence (PL)
spectra gave some structural insight (Figure 4.3b and 4.3c). For the unannealed films
(Figure 4.3b), we see characteristic 0 – 0 transitions at 350 nm with a sharper vibronic
band at 370 nm, which are typical for carbazole and are similar to our previous studies.
Peaks around 405 to 430 nm corresponding to excimer emission are not prominent.
51
Both
low molecular weight syndiotactic polymer (8a) and atactic polymer (9a) show lower PL
intensity than isotactic (6a) and high molecular weight syndiotactic polymer (7a), implying
more aggregation in polymers 8a and 9a for unannealed films. Similar spectral shapes are
observed in the case of annealed thin films (Figure 4.3c). For the atactic polymer 9a, there
is no effect of annealing giving the same PL intensity for both unannealed and annealed
thin films. Interestingly, for the polymers 6a and 7a, the PL intensity is strongly
diminished, suggesting aggregation based PL quenching, and thus providing some
evidence towards enhanced π – π stacking on annealing with the isotactic and high
molecular weight syndiotactic polymers. On the other hand, for polymer 8a, on annealing
the PL intensity is increased and the excimer peaks are further diminished, suggesting
reduced π – π stacking.
89

Figure 4.3 (a) HOMO and LUMO of PCzETPMA repeating unit. (b) PL spectra of
PCzETPMA polymers as-cast films. (c) PL spectra of PCzETPMA polymers films after
annealing at 210

C for 30 mins.
90

To study the morphology more precisely, the thin films were examined by grazing
incidence X-ray diffraction (GIXRD); however, no peaks were observed for polymers 6a
– 9a with or without annealing (Appendix C), which is in agreement with our previous
studies indicating the polymers are largely amorphous. The findings from GIXRD are also
consistent with DSC where no prominent peaks were observed (Appendix C). While
GIXRD gave no insight about the morphology of the thin films, we moved to atomic force
microscopy (AFM) which gave some insight for the thin film surface morphology. For thin
films of polymer 7a – 9a, the films are very smooth with rms surface roughness less than
1 nm observed, while only for polymer 6a, the film is slightly rougher with surface
roughness of 2.08 nm (Appendix C). For polymer 6a, the thin film contains multiple
elongated features of ~50 - 60nm, which may be due to short-range ordering of isotactic
chains, while for atactic polymer 9a, the film contains multiple isolated circular monticules
of 30nm in height, which can be agglomerations of atactic chains. Similar topology images
are obtained in literature for PVK thin films.
52
For polymers 7a and 8a, the thin film
morphology doesn’t have any prominent features.
To gain further insight, we elected to turn to simulations to model chain and bulk
structures. We used a similar approach as in our previous study
29
using DFT (Appendix
C). The chains of polymers (atactic, isotactic and syndiotactic) were optimized by using
B3LYP/6-31+G in Q-Chem 5.2.
53
From the DFT – optimized structures with 40 repeating
units, there is a significant difference between the polymers (Figure 4.4a). The atactic
structure is more randomized and clumped with respect to the isotactic and syndiotactic
structures. In contrast, the isotactic polymer shows an elongated structure but with
disordered backbone. On the other hand, the syndiotactic polymer exhibits a curved helical
backbone. This type of super helical structure is well known in syndiotactic PMMA
91

polymers.
54
While the atactic polymer shows no π – π stacking with disorganized pendant
units, the isotactic polymer shows some π – π stacked dimers and trimers within the
polymer chain. Interestingly such π – π stacked trimers were missing in the syndiotactic
polymer and are limited to few π – π stacked dimers.

Figure 4.4 (a) DFT – optimized structures of PCzETPMA polymers with 40 repeating
units and highlighted polymer backbone. (b) Mapping of carbazole moieties from MD
simulated thin films of 64 chains showing short range ordering (blue labelling).
To understand the effect of annealing and to see how the polymer packs in a thin
film, we moved to MD simulations (Appendix C). From these MD simulations, we
observed that as the films were annealed, the interactions between the chains are enhanced
in the case of isotactic and syndiotactic polymers. Upon mapping the carbazole moieties
(Figure 4.4b), we see short range π – π stacked ordering between multiple chains in the
case of isotactic and syndiotactic polymers, whereas such ordering is absent in the atactic
polymer and is limited to π – π stacked dimers and trimers. Such limited π – π stacking in
the atactic polymer explains the low µh observed for polymer 9a. Although both isotactic
92

and syndiotactic polymers show π – π stacked short range ordering between multiple chains
(not all instances are highlighted in figure 4.4b), the isotactic polymer clearly shows more
enhanced π – π stacked arrangements than the syndiotactic counterpart, which explains
polymer 6a having µh two orders of magnitude higher than polymer 8a. All MD
simulations were done for 20 repeating units and hence, don’t provide any insight for the
high molecular weight syndiotactic polymer 7a. More intensive studies are required for the
high molecular weight syndiotactic polymer to understand the dramatic increase in the
charge carrier mobility.
4.4 Conclusion
Here we have reported the effect of tacticity, annealing and molecular weight in
NCPEPs on the charge carrier mobility using PCzETPMA as a model polymer.
Specifically, this is the first report of charge carrier mobilities in syndiotactic NCPEPs. The
isotactic polymer gave the most consistent charge carrier mobility comparable with
conjugated polymers. While a low molecular weight syndiotactic polymer gave similar
charge carrier mobility to the atactic counterpart, a high molecular weight syndiotactic
polymer gave an unprecedented result surpassing P3HT by an order of magnitude. It is
found that enhanced charge carrier mobility in isotactic and high molecular weight
syndiotactic polymers is likely due to interchain short range ordering found in thin films
as simulated via MD. These results show that in NCPEPs, tacticity, spacer length and
molecular weight are not independent and show a complex relationship, which in some
cases leads to charge carrier mobilities exceeding well known conjugated polymers.

93

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Bibliography
Sanket was born in Rourkela, India in 1993. He then moved to Bhubaneswar, India where
he attended his high-school at D.A.V Public School. After completion, in 2011 he attended
National Institute of Science Education and Research (NISER), Bhubaneswar, India for his
5-year integrated master’s degree in Chemistry and graduated in the spring of 2016. During
his masters, he was working in the field of material chemistry, particularly examining
boron based polymers for Organic Light Emitting Devices (OLED) under the guidance of
Prof. V. Krishnan. In fall of 2016 he began his PhD studies in Organic Chemistry at
University of Southern California (USC) and joined Prof. Barry Thompson’s Research
Group in the year 2017 to study electroactive polymers for optoelectronic applications.

103

Appendix A

Chapter 2: Converging the Hole Mobility of Poly(2-N-carbazolylethyl acrylate) with
Conjugated Polymers by Tuning Isotacticity

A.1 General
All reagents from commercial sources were used without further purification,
unless otherwise noted. All reactions were performed under dry N2, unless otherwise noted.
All dry reactions were performed with glassware that was flamed under high vacuum and
backfilled with N2. Flash chromatography was performed using a Teledyne CombiFlash Rf
instrument in combination with RediSep Rf normal phase disposable columns. Solvents
were purchased from VWR and used without further purification except for THF, which
was dried over sodium/benzophenone before being distilled.
All compounds were characterized by
1
H NMR (400 MHz) and
13
C NMR (100
MHz) on a Mercury 400. Polymer
1
H NMRs (600 MHz) and
13
C NMRs (150 MHz) were
obtained on a Varian VNMRS-600. For polymer molecular weight determination, polymer
samples were dissolved in HPLC grade o-dichlorobenzene at a concentration of 0.5 mg/ml,
briefly heated and then allowed to turn to room temperature prior to filtering through a 0.2
μm PTFE filter for PCzEA polymers. SEC was performed using HPLC grade o-
dichlorobenzene at a flow rate of 1 ml/min on one 300 x 8.0 mm LT6000L Mixed High
Org column (Viscotek) at 60 °C using a Viscotek GPC Max VE 2001 separation module
and a Viscotek TDA 305 RI detector. The instrument was calibrated vs. polystyrene
standards (1,050 – 3,800 000 g/mol) and data was analyzed using OmniSec 4.6.0 software.
104

Cyclic voltammetry was collected using an EG&G instruments Model 263A
potentiostat under the control of PowerSuite Software. A standard three electrode cell
based on a Pt wire working electrode, a silver wire pseudo reference electrode (calibrated
vs. Fc/Fc
+
which is taken as 5.1 eV vs. vacuum) and a Pt wire counter electrode was purged
with nitrogen and maintained under nitrogen atmosphere during all measurements.
Acetonitrile was distilled over CaH2 prior to use. Tetrabutyl ammonium
hexafluorophosphate (0.1 M) was used as the supporting electrolyte for polymer films.
Polymer films were made by spin coating polymer solution over cleaned ITO substrate and
dried under nitrogen prior to measurement. Polymer solutions were prepared in chloroform
at a concentration of 7 mg/ml.
For thin film measurements polymers were spin coated onto pre-cleaned glass
slides from chloroform solutions (7 mg/mL). UV-vis absorption spectra were obtained on
a Perkin-Elmer Lambda 950 spectrophotometer. Photoluminescence (PL) measurements
were performed on a Horiba Jobin Yvon NanoLog Spectrofluorometer System Model FL-
1039/40 with a 450 W Xe Lamp. The thickness and crystallinity measurements of the thin
films were obtained using Rigaku Diffractometer Ultima IV using Cu Kα radiation source
(λ= 1.54 Å) in the reflectivity and X-Ray diffraction mode, respectively.
All steps of device fabrication and testing were performed in air. ITO-coated glass
substrates (10 Ω/ ☐, Thin Film Devices Inc.) were sequentially cleaned by sonication in
detergent, de-ionized water, tetrachloroethylene, acetone, and isopropyl alcohol, and dried
in a nitrogen stream. A thin layer of PEDOT: PSS (Baytron® P VP AI 4083, filtered with
a 0.45 μm PVDF syringe filter – Pall Life Sciences) was first spin-coated on the pre-cleaned
ITO-coated glass substrate and annealed at 120 °C for 60 minutes under vacuum. Polymer
solutions (7 mg/ml) were prepared in 2% solution of toluene in chloroform and stirred for
105

24 hours at room temperature. The polymer active layer was spin-coated (with a 0.45 μm
PTFE syringe filter – Pall Life Sciences) on top of the PEDOT: PSS layer. Films were
placed in a nitrogen cabinet for 20 minutes or were annealed at different temperatures
(105
0
C or 150
0
C) for 30 minutes before being transferred to a vacuum chamber. The
substrates were pumped down to a high vacuum and aluminum (100 nm) was thermally
evaporated at 3 – 4 Å/s using a Denton Benchtop Turbo IV Coating System onto the active
layer through shadow masks to define the active area of the devices as 5.18 mm
2
.
Mobility was measured using a hole-only device configuration (ITO/PEDOT:
PSS/Polymer/Al) in the space charge limited current regime. The dark current was
measured under ambient conditions. At sufficient potential the mobilities of charges in the
device can be determined by fitting the dark current to the model of SCL current and
described by equation 1:
𝐽 𝑆𝐶𝐿 𝐶 =
9
8
𝜀 𝑅 𝜀 0
𝜇 𝑉 2
𝐿 3
(1)
where JSCLC is the current density, ε0 is the permittivity of space, εR is the dielectric
constant of the polymer (assumed to be 3), µ is the zero-field mobility of the majority
charge carriers, V is the effective voltage across the device (V = Vapplied – Vbi – Vr), and L
is the polymer layer thickness. The series and contact resistance of the hole-only device
(35-40 Ω) was measured using a blank (ITO/PEDOT/Al) configuration and the voltage
drop due to this resistance (Vr) was subtracted from the applied voltage. The built-in
voltage (Vbi), which is based on the relative work function difference of the two electrodes,
was also subtracted from the applied voltage. The built-in voltage can be determined from
106

the transition between the ohmic region and the SCL region and is found to be about 0.6
V.
A.2 Synthesis
Synthetic procedures for the synthesis of N-(2' – hydroxyethyl) carbazole and 2-( 9H–
carbazol– 9– yl)ethyl acrylate were used without modifications as reported in the
literature.
1,2

Scheme A.1. Synthesis of PCzEA polymers.

107

Radical Polymerization for PCzEA (4a-4e). Monomer 3 was placed in a 5ml schlenk
flask without or with some Lewis acid [Y(OTf)3 or Sc(OTf)3] (0.05eq). Dry solvent mixture
of toluene/n-butanol (1 mg/ml) was added via syringe followed by quickly adding AIBN
(0.01eq) in one portion. The solution was degassed with N2 for 10m, then heated to 100
o
C
for 7d. Reaction mixtures were cooled to room temperature and precipitated into cold
methanol twice. After second precipitation polymers were collected via filtration and kept
under vacuum until dry.
Anionic Polymerization for PCzEA with n-BuLi (4f-4h). Monomer 3 was placed in a
15ml schlenk flask. Dry toluene (0.4 M) was added via syringe followed by quickly adding
n-BuLi in varied portion via syringe. The flask was placed inside a chiller and kept at 0
o
C
for 24h. Reaction mixtures were removed from chiller and were allowed to warm-up to
room temperature with finally precipitating into cold methanol twice. After second
precipitation polymers were collected via filtration and kept under vacuum until dry.
Anionic Polymerization for PCzEA with n-BuLi (4f-4h). Chalcone (0.33eq) was placed
in a 15ml schlenk flask and EtMgCl (0.33eq) was added via syringe. Dry toluene (0.4 M)
was added via syringe. The solution was heated at 30
o
C for 30min followed by addition of
monomer 3 in one portion. The solution was then kept at 30
o
C for 24h. Reaction mixtures
were cooled to room temperature and precipitated into cold methanol twice. After second
precipitation polymers were collected via filtration and kept under vacuum until dry.
Low isotactic polymers (4a-4e) are easily soluble in polar halogenated solvents like
dichloromethane and chloroform up to even 50 mg/ml, while intermediate isotactic
polymers (4f-4h) are also soluble in polar halogenated solvents but only up to 30 mg/ml
with slight elevated temperature (30-35
0
C) and high isotactic polymer (4i) is least soluble
and only soluble in chloroform at 7 mg/ml at room temperature.
108

A.3 Polymer NMR

Figure A.1
1
H NMR of PCzEA in CDCl3 at 50 °C.
109

Figure A.2
13
C NMR of PCzEA in CDCl3 at 50 °C.
110

Figure A.3
13
C NMR of PCzEA in CDCl3 at 50 °C, zoomed from 30-70 ppm.
111

Figure A.4 2D HSQC NMR of PCzEA with m = 50.7. From the single bond correlation
spectra, we can see that peak at 34.3 ppm in
13
C NMR has a strong correlation with peak
at 1.15 ppm in
1
H NMR.

112

Figure A.5 2D HSQC NMR of PCzEA with m = 94.7. From the single bond correlation
spectra, we can see that peak at 33.45 ppm in
13
C NMR has a strong correlation with
peaks at 0.87 ppm and 1.37 ppm in
1
H NMR.

113

A.4 UV-Vis Spectroscopy

Figure A.6 Absorption profile of PCzEA films, a) non-annealed, b) annealed at 150
o
C
for 30min.
114

A.5 X-Ray Diffraction

Figure A.7 X-Ray diffraction pattern for PCzEA film after annealing at 150
0
C for 30min.
Peak at 0.1 and 0.5 (2θ) is the direct beam from the instrument.

115

Table A.1 Polymer GIXRD data.
Polymer 2θ
(degrees)
d100 (Å) FWHM (degrees) Crystallite size
(nm)
4a 0.459 19.23 0.246 32.28
4b 0.501 17.63 0.229 34.68
4c 0.508 17.37 0.253 31.39
4d 0.532 16.60 0.245 32.41
4e 0.536 16.48 0.245 32.41
4f 0.465 19.00 0.260 30.54
4g 0.458 19.28 0.210 37.82
4h 0.504 17.52 0.260 30.54
4i 0.456 19.35 0.249 31.89

116

A.6 Polymer Mobility Data
Table A.2 Hole mobilities of PCzEA polymers in thin films spin coated from 2% Toluene
in chloroform (7 mg/ml) and annealed at 105
0
C for 30min. Results are an average of at-
least 6 pixels.
Polymer Hole Mobility
(µh) (cm
2
V
-1
s
-1
)
4a (6.15±0.22) x 10
-6

4b (1.05±0.55) x 10
-6

4c (1.17±1.01) x 10
-6

4d (2.21±0.20) x 10
-6

4e (3.38±0.51) x 10
-6

4f (1.16±0.84) x 10
-5

4g (2.11±0.39) x 10
-5

4h (2.65±0.47) x 10
-5

4i (4.06±1.08) x 10
-5

117

A.7 Differential Scanning Calorimetry (DSC)

Figure A.8 DSC trace of PCzEA polymers (4a – 4i).

118

A.8 Cyclic Voltammetry (CV)

Figure A.9 a) Atactic PCzEA polymer (m = 45.5) b) Isotactic PCzEA polymer (m =
94.7). The rest of the polymers gave similar spectra.

119

Table A.3. Electrochemical HOMO values, Optical Band Gaps, and Thermal properties of
family of isotactic PCzEA.

Polymer Homo (eV)
a
Eg (eV)
b
Tm (
0
C) Tc (
0
C)
4a 5.85 3.45 104 98
4b 5.84 3.45 105 99
4c 5.83 3.45 110 105
4d 5.85 3.45 103 102
4e 5.85 3.45 102 99
4f 5.83 3.45 97 94
4g 5.84 3.45 96 90
4h 5.84 3.45 94 87
4i 5.83 3.45 88 84

a
Cyclic voltammetry (vs Fc/Fc
+
) in acetonitrile, 0.1M TBAPF6.
b
Calculated from the
absorption band edge in thin films, Eg = 1240/λedge.

120

A.9 References
(1) Farah, A. A.; Pietro, W. J. Synthesis and Characterization of Multifunctional
Polymers via Atom Transfer Radical Polymerization of N-(Ω′-Alkylcarbazolyl)
Methacrylates Initiated by Ru(II) Polypyridyl Chromophores. J. Polym. Sci. Part A
Polym. Chem. 2005, 43 (23), 6057–6072.
(2) Gulfidan, D.; Sefer, E.; Koyuncu, S.; Acar, M. H. Neutral State Colorless
Electrochromic Polymer Networks: Spacer Effect on Electrochromic Performance.
Polymer 2014, 55 (23), 5998–6005.
(3) Patterson, A. L. The Scherrer Formula for X-Ray Particle Size Determination.
Phys. Rev. 1939, 56 (10), 978–982.

121

Appendix B

Chapter 3: Influence of Alkyl Chain Spacer Length on the Charge Carrier Mobility
of Isotactic Poly (N-carbazolylalkyl acrylates)
B.1. General
All reagents from commercial sources were used without further purification,
unless otherwise noted. All reactions were performed under dry N2, unless otherwise noted.
All dry reactions were performed with glassware that was flamed under high vacuum and
backfilled with N2. Flash chromatography was performed using a Teledyne CombiFlash Rf
instrument in combination with RediSep Rf normal phase disposable columns. Solvents
were purchased from VWR and used without further purification except for Toluene, which
was dried over CaH2 before being distilled and stored under 3A sieves.
All compounds were characterized by
1
H NMR (400 MHz) and
13
C NMR (100
MHz) on a Mercury 400. Polymer
1
H NMRs (600 MHz) and
13
C NMRs (150 MHz) were
obtained on a Varian VNMRS-600. For polymer molecular weight determination, polymer
samples were dissolved in HPLC grade o-dichlorobenzene at a concentration of 0.5 mg/ml,
briefly heated and then allowed to return to room temperature prior to filtering through a
0.2 μm PTFE filter. SEC was performed using HPLC grade o-dichlorobenzene at a flow
rate of 1 ml/min on one 300 x 8.0 mm LT6000L Mixed High Org column (Viscotek) at 60
°C using a Viscotek GPC Max VE 2001 separation module and a Viscotek TDA 305 RI
detector. The instrument was calibrated vs. polystyrene standards (1,050 – 3,800 000
g/mol) and data was analyzed using OmniSec 4.6.0 software.
122

Cyclic voltammetry was collected using an EG&G instruments Model 263A
potentiostat under the control of PowerSuite Software. A standard three electrode cell
based on a Pt wire working electrode, a silver wire pseudo reference electrode (calibrated
vs. Fc/Fc
+
which is taken as 5.1 eV vs. vacuum) and a Pt wire counter electrode was purged
with nitrogen and maintained under nitrogen atmosphere during all measurements.
Acetonitrile was distilled over CaH2 prior to use. Tetrabutyl ammonium
hexafluorophosphate (0.1 M) was used as the supporting electrolyte for polymer films.
Polymer films were made by spin coating polymer solution over cleaned ITO substrate and
dried under nitrogen prior to measurement. Polymer solutions were prepared in chloroform
at a concentration of 7 mg/ml.
For thin film measurements polymers were spin coated onto pre-cleaned glass
slides from chloroform solutions (7 mg/mL). UV-vis absorption spectra were obtained on
a Perkin-Elmer Lambda 950 spectrophotometer. Photoluminescence (PL) measurements
were performed on a Horiba Jobin Yvon NanoLog Spectrofluorometer System Model FL-
1039/40 with a 450 W Xe Lamp. The thickness and crystallinity measurements of the thin
films were obtained using Rigaku Diffractometer Ultima IV using Cu Kα radiation source
(λ= 1.54 Å) in the reflectivity and X-Ray diffraction mode, respectively.
All steps of device fabrication and testing were performed in air. ITO-coated glass
substrates (10 Ω/ ☐, Thin Film Devices Inc.) were sequentially cleaned by sonication in
detergent, de-ionized water, tetrachloroethylene, acetone, and isopropyl alcohol, and dried
in a nitrogen stream. A thin layer of PEDOT: PSS (Baytron® P VP AI 4083, filtered with
a 0.45 μm PVDF syringe filter – Pall Life Sciences) was first spin-coated on the pre-cleaned
ITO-coated glass substrate and annealed at 120 °C for 60 minutes under vacuum. Polymer
solutions (7 mg/ml) were prepared in 2% solution of toluene in chloroform and stirred for
123

24 hours at room temperature. The polymer active layer was spin-coated (with a 0.45 μm
PTFE syringe filter – Pall Life Sciences) on top of the PEDOT: PSS layer. Films were
placed in a nitrogen cabinet for 20 minutes or were annealed at different temperatures
(105
0
C or 150
0
C) for 30 minutes before being transferred to a vacuum chamber. The
substrates were pumped down to a high vacuum and aluminum (100 nm) was thermally
evaporated at 3 – 4 Å/s using a Denton Benchtop Turbo IV Coating System onto the active
layer through shadow masks to define the active area of the devices as 5.18 mm
2
.
Mobility was measured using a hole-only device configuration (ITO/PEDOT:
PSS/Polymer/Al) in the space charge limited current regime. The dark current was
measured under ambient conditions. At sufficient potential the mobilities of charges in the
device can be determined by fitting the dark current to the model of SCL current and
described by equation 1:
𝐽 𝑆𝐶𝐿 𝐶 =
9
8
𝜀 𝑅 𝜀 0
𝜇 𝑉 2
𝐿 3
(1)
where JSCLC is the current density, ε0 is the permittivity of space, εR is the dielectric constant
of the polymer (assumed to be 3), µ is the zero-field mobility of the majority charge
carriers, V is the effective voltage across the device (V = Vapplied – Vbi – Vr), and L is the
polymer layer thickness. The series and contact resistance of the hole-only device (35-40
Ω) was measured using a blank (ITO/PEDOT/Al) configuration and the voltage drop due
to this resistance (Vr) was subtracted from the applied voltage. The built-in voltage (Vbi),
which is based on the relative work function difference of the two electrodes, was also
subtracted from the applied voltage. The built-in voltage can be determined from the
transition between the ohmic region and the SCL region and is found to be about 0.6 V.
124

Simulations were carried out at the USC High Performance Computing Cluster
(Discovery). Discovery has over 400 compute nodes with 1200 cores of 2.60 GHz Xeon
and 2.90 GHz EPYC processors. All DFT calculation were done in 2.60 GHz Xeon
processors using up to 128 Gb memory, while MD calculation were done in 2.90 GHz
EPYC processors using up to 32 Gb memory.
B.2. Synthesis

Scheme B.1. Synthesis of monomers and PCzXA via direct polymerization.
125

Synthetic procedures for the synthesis of N-(2’- hydroxyethyl) carbazole and 2-(
9H – carbazole-9-yl) ethyl acrylate were used without modifications as reported in the
literature.
1,2
Methyl acrylate was freshly distilled from CaH2 and was stored over 4A
Sieves. Carbazole was freshly recrystallized from 200 proof ethanol.
General method for synthesis of compounds (4b - 4d): Synthesis was adapted from the
literature with slight modification.
3
In a 50 mL three neck round bottom flask, to a stirred
solution of carbazole (10 mmol) in toluene (15 mL), benzyltriethylammonium chloride
(BTEAC) (150 mg) and 50% aqueous solution of potassium hydroxide (15 mL) was added
and stirred for 60 mins. Then excess amount of alkyl dihalide (100 mmol) was added and
the solution was stirred overnight. After neutralization with 1M HCl, brine was added to
the reaction mixture, which was then, which was then extracted with ethyl acetate (50 mL
x 3). The organic layers were dried, concentrated under reduced pressure and the residue
was purified by column chromatography (hexane/ethyl acetate). Yield: 78% (4b), 70% (4c)
and 61% (4d).
General method for synthesis of compounds (5b – 5d): Synthesis was adapted from
literature with slight modification.
3
In a 100 mL three neck round bottom flask, to a mixture
of monomer (4b – 4d) (10 mmol) in chloroform (25 mL), 25 mL of water is added,
followed by addition of sodium acrylate (40 mmol) and tetrabutylammonium bromide (2.5
mmol). The mixture was stirred for 72 h at 50
°
C. The organic layer was extracted with
chloroform, dried over anhydrous MgSO4 and concentrated under reduced pressure. The
residue was purified by column chromatography (hexane/DCM). Yield: 79% (5b), 67%
(5c) and 55% (5d).
126

General method for synthesis of polymers (6a – 6d): Acrylate monomers were placed in
a N2 filled 25 mL Schlenk flask at 0
°
C. Dry toluene (0.4 M) was added via syringe followed
by quickly adding n-BuLi (10 mol%) via syringe. The flask was kept at 0
°
C for 24 h. The
reaction mixture was removed from 0
°
C after 24 h and 1 mL methanol was added to quench
the reaction before fully warming to room temperature. The reaction mixture was then
concentrated under reduced pressure and was precipitated into 200 mL cold methanol
twice. After the second precipitation polymers were collected via filtration and kept under
vacuum for 24 h.
Table B.1 Polymer yield and Molecular Weights for Polymers 6a – 6d.
Polymer Yield (%) Mn (kg/mol)
a

6a 58 6.2
6b 65 4.1
6c 62 3.7
6d 51 2.8

a
Determined by SEC with polystyrene standards and o-DCB eluent.
General method for synthesis of compounds (7b – 7f): Synthesis was adapted from the
literature with slight modification.
4
In a 100 mL single neck round bottom flask, to a
solution of carbazole (10 mmol) in DMF (25 mL), NaH (60% dispersion in mineral oil, 15
mmol) was added at 0
°
C. After stirring for one hour, 15 mmol of alcohol (in the case of
7b, THP protected alcohol was used to avoid formation of a carbazole dimer) was added
at 0
°
C and the mixture was warmed to room temperature and was stirred for 36 h. The
mixture was poured into water and extracted with diethyl ether. The organic phase was
washed with brine, dried over anhydrous MgSO4 and concentrated under reduced pressure.
127

The residue was purified by column chromatography (hexane/ethyl acetate). Yield: 55%
(7b), 69% (7c), 59% (7d), 56% (7e) and 62% (7f).
Synthesis of polymer (9a): Synthesis was adapted from the literature with slight
modification.
5
Methyl Acrylate was placed in a N2 filled 25 mL Schlenk flask at -20
°
C.
Dry toluene (1 M) was added via syringe followed by quickly adding n-BuLi (10 mol%)
via syringe. The flask was kept at -20
°
C for 48 h. The reaction mixture was removed from
-20
°
C after 48 h and 1 mL methanol was added to quench the reaction before fully warming
to room temperature. The reaction mixture was then concentrated under reduced pressure
and was precipitated into 200 mL cold methanol twice. After the second precipitation
polymer was collected via filtration and kept under vacuum for 24 h.
Synthesis of polymer (9b): Synthesis was adapted from the literature with slight
modification.
5
Methyl Acrylate was placed in N2 filled 25 mL Schlenk flask at 0
°
C. Dry
toluene (1 M) was added via syringe followed by quickly adding phenylmagnesium
bromide (2 M in diethyl ether, 10 mol%) via syringe. The flask was kept at 0
°
C for 24 h.
The reaction mixture was removed from 0
°
C after 24 h and 1 mL methanol was added to
quench the reaction before fully warming to room temperature. The reaction mixture was
then concentrated under reduced pressure and was precipitated into 200 mL cold methanol
twice. After second precipitation polymer was collected via filtration and kept under
vacuum for 24 h.
General method for synthesis of polymers (10-15): Synthesis was adapted from the
literature with slight modification.
6
In an oven dried, N2 filled 25 mL Schlenk flask,
polymer 9a/9b (1.0 mmol) was added with ZnTac24 (1.25 mol%), DMAP (20 mol%),
alcohol (7a – 7f) (1.2 mmol) and dry toluene (5 mL). The Schlenk flask was equipped with
128

a dean stark apparatus filled with 4A sieves. The flask was then transferred to a preheated
oil bath at 130
°
C. After 48 h, the mixture was concentrated under reduced pressure and
was precipitated thrice in 200 mL cold methanol. After the final precipitation, the residue
was washed with hot diethyl ether multiple times. The polymer was then finally
reprecipitated in 200 mL cold methanol. The product was then collected via filtration and
kept under vacuum for 24 h.

129

B.3 NMR Spectroscopy

Figure B.1
1
H NMR of 75% isotactic poly(methyl acrylate) (9a).

Figure B.2
1
H NMR of 87% isotactic poly(methyl acrylate) (9b).
130

Figure B.3 Calculation of Isotacticity from
1
H NMR for 9a and 9b.

Figure B.4
1
H NMR spectra of 87% isotactic PMA (9b) and trans-esterified PCzEA
(10b).
131

Figure B.5
1
H NMR of 87% isotactic 2C-spacer-spacerafter transesterification (10b).

Figure B.6
1
H NMR of 87% isotactic 4C-spacer after transesterification (11b).
132

Figure B.7
1
H NMR of 87% isotactic 6C-spacer after transesterification (12b).

Figure B.8
1
H NMR of 87% isotactic 8C-spacer after transesterification (13b).
133

Figure B.9
1
H NMR of 87% isotactic 10C-spacer after transesterification (14b).

Figure B.10
1
H NMR of 87% isotactic 12C-spacer after transesterification (15b).
134

Figure B.11
1
H NMR of 75% isotactic 2C-spacer after transesterification (10a).

Figure B.12
1
H NMR of 75% isotactic 4C-spacer after transesterification (11a).
135

Figure B.13
1
H NMR of 75% isotactic 6C-spacer after transesterification (12a).

Figure B.14
1
H NMR of 75% isotactic 8C-spacer after transesterification (13a).
136

Figure B.15
1
H NMR of 75% isotactic 10C-spacer after transesterification (14a).

Figure B.16
1
H NMR of 75% isotactic 12C-spacer after transesterification (15a).

137

B.4 UV -Vis Spectroscopy

Figure B.17 Annealed 75% isotactic polymers.

Figure B.18 Annealed 87% Isotactic polymers.
138

B. 5 X-Ray Diffraction

Figure B.19 Annealed 75% Isotactic polymers.

Figure B.20 Annealed 87% Isotactic polymers.

139

B.6 Photoluminescence

Figure B.21 Annealed 75% Isotactic polymers.

Figure B.22 Annealed 87% Isotactic polymers.

140

B.7 Hole Mobility

Figure B.23 Unannealed 75% Isotactic polymers.

Figure B.24 Annealed 75% Isotactic polymers.

141

Figure B.25 Unannealed 87% Isotactic polymers.

Figure B.26 Annealed 87% Isotactic polymers.
142

B.8 Cyclic Voltammetry

Figure B.27 CV scan of 75% isotactic 2C-spacer after transesterification (10a).

Figure B.28 CV scan of 87% isotactic 2C-spacer after transesterification (10b).
143

Figure B.29 CV scan of 75% isotactic 4C-spacer after transesterification (11a).

Figure B.30 CV scan of 87% isotactic 4C-spacer after transesterification (11b).
144

Figure B.31 CV scan of 75% isotactic 6C-spacer after transesterification (12a).

Figure B.32 CV scan of 87% isotactic 6C-spacer after transesterification (12b).
145

Figure B.33 CV scan of 75% isotactic 8C-spacer after transesterification (13a).

Figure B.34 CV scan of 87% isotactic 8C-spacer after transesterification (13b).

146

Figure B.35 CV scan of 75% isotactic 10C-spacer after transesterification (14a).

Figure B.36 CV scan of 87% isotactic 10C-spacer after transesterification (14b).
147

Figure B.37 CV scan of 75% isotactic 12C-spacer after transesterification (15a).

Figure B.38 CV scan of 87% isotactic 12C-spacer after transesterification (15b).

148

Table B.2 Electrochemical HOMO values for transesterified polymers.
Polymer Onset (V) HOMO (eV)
a

10a 0.74 5.84
10b 0.72 5.82
11a 0.73 5.83
11b 0.72 5.82
12a 0.75 5.85
12b 0.73 5.83
13a 0.75 5.85
13b 0.76 5.86
14a 0.74 5.84
14b 0.73 5.83
15a 0.75 5.85
15b 0.74 5.84

a
Cyclic Voltametry (vs Fc/Fc
+
) in acetonitrile.

149

B.9 DSC

Figure B.39 DSC scan of 75% isotactic 2C-spacer after transesterification (10a).

Figure B.40 DSC scan of 75% isotactic 4C-spacer after transesterification (11a).
150

Figure B.41 DSC scan of 75% isotactic 6C-spacer after transesterification (12a).

Figure B.42 DSC scan of 75% isotactic 8C-spacer after transesterification (13a).
151

Figure B.43 DSC scan of 75% isotactic 10C-spacer after transesterification (14a).

Figure B.44 DSC scan of 75% isotactic 12C-spacer after transesterification (15a).

152

Figure B.45 DSC scan of 87% isotactic 2C-spacer after transesterification (10b).

Figure B.46 DSC scan of 87% isotactic 4C-spacer after transesterification (11b).
153

Figure B.47 DSC scan of 87% isotactic 6C-spacer after transesterification (12b).

Figure B.48 DSC scan of 87% isotactic 8C-spacer after transesterification (13b).

154

Figure B.49 DSC scan of 87% isotactic 10C-spacer after transesterification (14b).

Figure B.50 DSC scan of 87% isotactic 12C-spacer after transesterification (15b).

155

B.10 Simulations
A database of atactic and fully isotactic PCzXA chains with lengths of 20 and 40
monomers for each carbon spacer length (two to twelve carbons) was generated. These
chains were initially optimized using the B3LYP/6-31+G(d) level of theory using Q-Chem
5.0. From the DFT optimized structures of PCzXA polymers with 40 repeating units, there
is clearly a significant difference between the atactic and isotactic structures. Where the
atactic structure is more randomized and clumped, the isotactic structures are elongated
with all the pendant carbazole units surrounding the outside of a helical backbone. This
elongated orientation of the isotactic structure is probably the major factor affecting the µh
through a single polymeric chain. As the carbon spacer is increased from two carbon to
twelve carbons for the isotactic polymers, the orientation of pendant carbazole units
becomes more disorganized and tends toward forming -stacked dimers and the disruption
of the helical arrangement of the carbazole moieties even though the backbone retains the
helical orientation. This type of helical structure is not uncommon and is seen in many
highly isotactic polymers. Looking down the axis of the polymer chains, we see that the
carbazoles are nicely oriented around the backbone with the four carbon and six carbon
spacers, as opposed to the two carbon spacer, which is more compact and slightly puckered.
As the spacer length increases from eight carbons to twelve carbons, the favorable
orientation is deviated, and the pendant groups are more randomly organized. To
understand the effect of annealing and how the polymers pack in a thin film, we turned to
MD simulations. The initial topology files for the 20 monomer chains (we limited the
molecular dynamic calculations to 20 monomers because of computational limitations)
were obtained from Automated Topology Builder (ATB) and Repository (Version 3.0).
Chains of each polymer were permitted to relax within the MD simulations for 1ns in
156

isolation at 300K (using the LAMMPS suite), according to the intramolecular components
of the GROMOS_54A7 force field, thus mimicking their arrangement in solution. A total
of 64 relaxed chains for each polymer was created for further simulations. These chains
were then placed in a large periodically bounded simulation box at periodic positions and
orientations, with sufficient space between chains to avoid interchain interactions. This
large simulation volume was then compressed over a period of 40 ps at 300K until the
density reached an average of 1.2 g/mL (density of PVK), thus mimicking the effect of
solvent evaporation. Afterward, we simulated a thin film morphology containing the
PCzXAs with the selected density within a simulation cube. We repeated the same
morphological simulations utilizing both the intra and intermolecular components of the
force field for annealing and equilibration effects. All simulations were performed at
constant volume and temperature was maintained using a Nosé−Hoover thermostat and
barostat with timesteps of 4 fs, using the LAMMPS suite. The morphologies were then
simulated with varying temperature from 300K to 425K for 4ns. The annealed films were
finally cooled down to room temperature over a further 4ns period, before equilibrating at
300K for a final of 4ns.
Detailed Simulation Steps:
Using IQmol molecular builder, an initial starting conformation was developed for
both random and completely isotactic polymers. These polymer chains were limited to 20
repeating units (<1000 atoms), because of computation limitations. Within IQmol itself,
once the initial conformation was made, the initial structure was optimized using Molecular
Mechanics and MMFF94 force field. Once energy optimization was done, using IQmol, a
Q-Chem input file was created for geometry optimization using Hartree-Fock (HF) theory
and the STO-6G basis set. Then the optimized geometry from HF/STO-6G was taken and
157

loaded into IQmol and another Q-Chem input file was created for geometry optimization
using the DFT (B3LYP) and 6-31+G* basis set to obtain our final optimized polymer
chains. It took approximately 14 – 21 days to complete the geometry optimization for the
polymer chains with 20 repeating unit (<1000 atoms).
Once these structures were optimized using Q-Chem, these structures are uploaded
to Automated Topology Builder (ATB) and Repository (Version 3.0), to get the necessary
topology files for molecular dynamics (MD) calculations. Generally, these topology file
contains all the different kinds of atoms present in the system, their masses, different bonds,
bond angles, bond dihedrals and improper dihedrals within the molecule to maintain the
connectivity of the atoms and avoiding formation of new bonds during MD simulations.
These topology files were built using GROMOS_54A7 force field and were downloaded
directly from the ATB Repository. Using these topology files and force field files, a 3D
MD simulation box of 200 Å was created with periodic boundary conditions and was
packed with 64 chains of the polymer using moltemplate. Moltemplate helps to create a
database of all the necessary details needed for MD calculations using LAMMPS.
158

Figure B.51 Relaxation of individual polymer chain from starting configuration at 0 K to
300 K.

Each chain of polymer was then permitted to relax within the MD simulation for 1
ns in isolation at 0 K in vacuum using the LAMMPS suite, according to the intramolecular
components of the GROMOS_54A7 force field. Then each chain was again permitted to
relax within the MD simulation for 1 ns in isolation at 300 K using the same LAMMPS
suite mimicking their behavior in solution as shown above. After that, this large simulation
volume was then compressed over a period of 40 ps at 300 K until the density of average
1.2 g/mL was reached, hence mimicking spin coating of the solution into a thin film. After
that, pressure was equilibrated to atmospheric pressure at constant volume and temperature
with timesteps of 4 fs using the LAMMPS suite as shown below.
159

Figure B.52 Formation of thin film morphology at 300 K.
To study the effect of thermal annealing, the, the same calculation methodology
was applied with slight variation. Once the density of 1.2 g/mL was reached, the
morphology was subjected with varying temperature, where temperature was increased
from 300 K to 425 K over 4 ns period, then the annealed films were again finally cooled
down to 300 K over a further 4 ns period, before equilibrating at 300 K and atmospheric
pressure for a final of 4 ns as shown below.
160

Figure B.53 Formation of thin film morphology at 300 K and thermal annealing
simulation.

Figure B.54 Optimized structure for atactic polymer with 2 carbon spacer and 20 repeating
units.
161

Figure B.55 Optimized structure for atactic polymer with 2 carbon spacer and 40
repeating units.

Figure B.56 Optimized structure for isotactic polymer with 2 carbon spacer and 20
repeating units.
162

Figure B.57 Optimized structure for isotactic polymer with 2 carbon spacer and 40
repeating units.

Figure B.58 Thin layer MD structure for atactic polymer with 2 carbon spacer at room-
temp.
163

Figure B.59 Thin layer MD structure for atactic polymer with 2 carbon spacers at room-
temp where all the carbazole moieties are highlighted.

Figure B.60 Thin layer MD structure for atactic polymer with 2 carbon spacers after
annealing.
164

Figure B.61 Thin layer MD structure for atactic polymer with 2 carbon spacers after
annealing where all the carbazole moieties are highlighted.

Figure B.62 Thin layer MD structure for isotactic polymer with 2 carbon spacers at
room-temp.

165

Figure B.63 Thin layer MD structure for isotactic polymer with 2 carbon spacers at
room-temp where all the carbazole moieties are highlighted.

Figure B.64 Thin layer MD structure for isotactic polymer with 2 carbon spacers after
annealing.
166

Figure B.65 Thin layer MD structure for isotactic polymer with 2 carbon spacers after
annealing where all the carbazole moieties are highlighted.

Figure B.66 Optimized structure for isotactic polymer with 4 carbon spacer and 20
repeating units.

167

Figure B.67 Optimized structure for isotactic polymer with 4 carbon spacer and 40
repeating units.

Figure B.68 Thin layer MD structure for isotactic polymer with 4 carbon spacers at room-
temp.
168

Figure B.69 Thin layer MD structure for isotactic polymer with 4 carbon spacers at
room-temp where all the carbazole moieties are highlighted.

Figure B.70 Thin layer MD structure for isotactic polymer with 4 carbon spacers after
annealing.
169

Figure B.71 Thin layer MD structure for isotactic polymer with 4 carbon spacers after
annealing where all the carbazole moieties are highlighted.

Figure B.72 Optimized structure for isotactic polymer with 6 carbon spacer and 20
repeating units.

170

Figure B.73 Optimized structure for isotactic polymer with 6 carbon spacer and 40
repeating units.

Figure B.74 Thin layer MD structure for isotactic polymer with 6 carbon spacers at room-
temp.
171

Figure B.75 Thin layer MD structure for isotactic polymer with 6 carbon spacers at
room-temp where all the carbazole moieties are highlighted.

Figure B.76 Thin layer MD structure for isotactic polymer with 6 carbon spacers after
annealing.
172

Figure B.77 Thin layer MD structure for isotactic polymer with 6 carbon spacers after
annealing where all the carbazole moieties are highlighted.

Figure B.78 Optimized structure for isotactic polymer with 8 carbon spacer and 20
repeating units.

173

Figure B.79 Optimized structure for isotactic polymer with 8 carbon spacer and 40
repeating units.

Figure B.80 Thin layer MD structure for isotactic polymer with 8 carbon spacers at room-
temp.
174

Figure B.81 Thin layer MD structure for isotactic polymer with 8 carbon spacers at
room-temp where all the carbazole moieties are highlighted.

Figure B.82 Thin layer MD structure for isotactic polymer with 8 carbon spacers after
annealing.
175

Figure B.83 Thin layer MD structure for isotactic polymer with 8 carbon spacer after
annealing where all the carbazole moieties are highlighted.

Figure B.84 Optimized structure for isotactic polymer with 10 carbon spacer and 20
repeating units.

176

Figure B.85 Optimized structure for isotactic polymer with 10 carbon spacer and 40
repeating units.

Figure B.86 Thin layer MD structure for isotactic polymer with 10 carbon spacers at room-
temp.
177

Figure B.87 Thin layer MD structure for isotactic polymer with 10 carbon spacers at
room-temp where all the carbazole moieties are highlighted.

Figure B.88 Thin layer MD structure for isotactic polymer with 10 carbon spacers after
annealing.
178

Figure B.89 Thin layer MD structure for isotactic polymer with 10 carbon spacers after
annealing where all the carbazole moieties are highlighted.

Figure B.90 Optimized structure for isotactic polymer with 12 carbon spacer and 20
repeating units.

179

Figure B.91 Optimized structure for isotactic polymer with 12 carbon spacer and 40
repeating units.

Figure B.92 Thin layer MD structure for isotactic polymer with 12 carbon spacers at room-
temp.
180

Figure B.93 Thin layer MD structure for isotactic polymer with 12 carbon spacers at
room-temp where all the carbazole moieties are highlighted.

Figure B.94 Thin layer MD structure for isotactic polymer with 12 carbon spacers after
annealing.
181

Figure B.95 Thin layer MD structure for isotactic polymer with 12 carbon spacers after
annealing where all the carbazole moieties are highlighted.

Figure B.96 Thin layer MD structure for isotactic polymer with 2 carbon spacers at room
temperature indicating individual chains.

182

Figure B.97 Thin layer MD structure for isotactic polymer with 2 carbon spacers after
annealing indicating individual chains.

Figure B.98 Thin layer MD structure for isotactic polymer with 4 carbon spacers at room
temperature indicating individual chains.
183

Figure B.99 Thin layer MD structure for isotactic polymer with 4 carbon spacers after
annealing indicating individual chains.

Figure B.100 Thin layer MD structure for isotactic polymer with 6 carbon spacers at
room temperature indicating individual chains.
184

Figure B.101 Thin layer MD structure for isotactic polymer with 6 carbon spacers after
annealing indicating individual chains.

Figure B.102 Thin layer MD structure for isotactic polymer with 8 carbon spacers at
room temperature indicating individual chains.

185

Figure B.103 Thin layer MD structure for isotactic polymer with 8 carbon spacers after
annealing indicating individual chains.

Figure B.104 Thin layer MD structure for isotactic polymer with 10 carbon spacers at
room temperature indicating individual chains.
186

Figure B.105 Thin layer MD structure for isotactic polymer with 10 carbon spacers after
annealing indicating individual chains.

Figure B.106 Thin layer MD structure for isotactic polymer with 12 carbon spacers at
room temperature indicating individual chains.
187

Figure B.107 Thin layer MD structure for isotactic polymer with 12 carbon spacers after
annealing indicating individual chains.

188

B.11 References
(1) Farah, A. A.; Pietro, W. J. Synthesis and Characterization of Multifunctional
Polymers via Atom Transfer Radical Polymerization OfN-(Ω′-Alkylcarbazolyl)
Methacrylates Initiated by Ru(II) Polypyridyl Chromophores. J. Polym. Sci. Part A Polym.
Chem. 2005, 43 (23), 6057–6072. https://doi.org/10.1002/pola.21027.
(2) Gulfidan, D.; Sefer, E.; Koyuncu, S.; Acar, M. H. Neutral State Colorless
Electrochromic Polymer Networks: Spacer Effect on Electrochromic Performance.
Polymer 2014, 55 (23), 5998–6005. https://doi.org/10.1016/j.polymer.2014.09.041.
(3) Barrett, C.; Choudhury, B.; Natansohn, A.; Rochon, P. Azocarbazole
Polymethacrylates as Single-Component Electrooptic Materials. Macromolecules 1998, 31
(15), 4845–4851. https://doi.org/10.1021/ma980155f.
(4) Dunkel, P.; Barosi, A.; Dhimane, H.; Maurel, F.; Dalko, P. I. Photoinduced Electron
Transfer (PET)-Mediated Fragmentation of Picolinium-Derived Redox Probes. Chem. - A
Eur. J. 2018, 24 (49), 12920–12931. https://doi.org/10.1002/chem.201801684.
(5) Matsuzaki, K.; Uryu, T.; Ishida, A.; Ohki, T.; Takeuchi, M. Stereoregularity of
Poly(Methyl Acrylate). J. Polym. Sci. Part A-1 Polym. Chem. 1967, 5 (8), 2167–2177.
https://doi.org/10.1002/pol.1967.150050832.
189

Appendix C
Chapter 4: Contrasting the Charge Carrier Mobility of Isotactic, Syndiotactic, and
Atactic Poly((N-carbazolylethylthio)propyl methacrylate)
C.1 General
All reagents from commercial sources were used without further purification,
unless otherwise noted. All reactions were performed under dry N2, unless otherwise noted.
All dry reactions were performed with glassware that was flamed under high vacuum and
backfilled with N2. Flash chromatography was performed using a Teledyne CombiFlash Rf
instrument in combination with RediSep Rf normal phase disposable columns. Toluene is
dried over CaH2 before being distilled and stored under 3A sieves. THF is dried over
sodium before being distilled and stored under 3A sieves.
All compounds were characterized by
1
H NMR (400 MHz) on a Mercury 400.
Polymer
1
H NMRs (600 MHz) and
13
C NMRs (150 MHz) were obtained on a Varian
VNMRS-600. For polymer molecular weight determination, polymer samples were
dissolved in HPLC grade trichlorobenzene at a concentration of 0.5 mg/ml, briefly heated
and then allowed to turn to room temperature prior to filtering through a 0.2 μm PTFE filter
for PCzETPMA polymers. SEC was performed using HPLC grade trichlorobenzene at a
flow rate of 1 ml/min on four 300 x 7.5 mm PL1110 Mixed High grade Organic column
(Agilent) at 80 °C using a Agilent PL-GPC separation module and a Agilent 1260 Infinity
II RI detector. The instrument was calibrated vs. polystyrene standards (1,050 – 3,800 000
g/mol) and data was analyzed using Agilent GPC/SEC software.
Cyclic voltammetry was collected using an EG&G instruments Model 263A
potentiostat under the control of PowerSuite Software. A standard three electrode cell
190

based on a Pt wire working electrode, a silver wire pseudo reference electrode (calibrated
vs. Fc/Fc
+
which is taken as 5.1 eV vs. vacuum) and a Pt wire counter electrode was purged
with nitrogen and maintained under nitrogen atmosphere during all measurements.
Acetonitrile was distilled over CaH2 prior to use. Tetrabutyl ammonium
hexafluorophosphate (0.1 M) was used as the supporting electrolyte for polymer films.
Polymer films were made by spin coating polymer solution over cleaned ITO substrate and
dried under nitrogen prior to measurement. Polymer solutions were prepared in chloroform
at a concentration of 7 mg/mL. Thermal gravimetric analysis (TGA) was performed on a
TGA Q50 instrument and samples were run in an alumina crucible under a flowing nitrogen
atmosphere with a heating rate of 10
o
C/min.
For thin film measurements polymers were spin coated onto pre-cleaned glass
slides from chloroform solutions (7 mg/mL). UV-vis absorption spectra were obtained on
a Perkin-Elmer Lambda 950 spectrophotometer. Photoluminescence (PL) measurements
were performed on a Horiba Jobin Yvon NanoLog Spectrofluorometer System Model FL-
1039/40 with a 450 W Xe Lamp. The thickness and crystallinity measurements of the thin
films were obtained using Rigaku Diffractometer Ultima IV using Cu Kα radiation source
(λ= 1.54 Å) in the reflectivity and X-Ray diffraction mode, respectively. For AFM,
polymers were spin coated onto pre-cleaned 111 Si single crystal wafer from chloroform
solutions (10 mg/mL).
All steps of device fabrication and testing were performed in air. ITO-coated glass
substrates (10 Ω/ ☐, Thin Film Devices Inc.) were sequentially cleaned by sonication in
detergent, de-ionized water, tetrachloroethylene, acetone, and isopropyl alcohol, and dried
in a nitrogen stream. A thin layer of PEDOT: PSS (Baytron® P VP AI 4083, filtered with
a 0.45 μm PVDF syringe filter – Pall Life Sciences) was first spin-coated on the pre-cleaned
191

ITO-coated glass substrate and annealed at 120 °C for 60 minutes under vacuum. Polymer
solutions (7 mg/mL) were prepared in 2% solution of toluene in chloroform and stirred for
24 hours at room temperature. The polymer active layer was spin-coated (with a 0.45 μm
PTFE syringe filter – Pall Life Sciences) on top of the PEDOT: PSS layer. Films were
placed in a nitrogen cabinet for 20 minutes or were annealed at different temperatures (120
o
C, 150
o
C or 210
o
C) for 30 minutes before being transferred to a vacuum chamber. The
substrates were pumped down to a high vacuum and aluminum (100 nm) was thermally
evaporated at 3 – 4 Å/s using a Denton Benchtop Turbo IV Coating System onto the active
layer through shadow masks to define the active area of the devices as 5.18 mm
2
.
Mobility was measured using a hole-only device configuration (ITO/PEDOT:
PSS/Polymer/Al) in the space charge limited current regime. The dark current was
measured under ambient conditions. At sufficient potential the mobilities of charges in the
device can be determined by fitting the dark current to the model of SCL current and
described by equation 1:
𝐽 𝑆𝐶𝐿 𝐶 =
9
8
𝜀 𝑅 𝜀 0
𝜇 𝑉 2
𝐿 3
(1)
where JSCLC is the current density, ε0 is the permittivity of space, εR is the dielectric constant
of the polymer (assumed to be 3), µ is the zero-field mobility of the majority charge
carriers, V is the effective voltage across the device (V = Vapplied – Vbi – Vr), and L is the
polymer layer thickness. The series and contact resistance of the hole-only device (30-35
Ω) was measured using a blank (ITO/PEDOT/Al) configuration and the voltage drop due
to this resistance (Vr) was subtracted from the applied voltage. The built-in voltage (Vbi),
which is based on the relative work function difference of the two electrodes, was also
192

subtracted from the applied voltage. The built-in voltage can be determined from the
transition between the ohmic region and the SCL region and is found to be about 0.6 V.
Simulations were carried out at the USC High Performancve Computing Cluster
(Discovery). Discovery has over 400 compute nodes with 1200 cores of 2.60 GHz Xeon
and 2.90 GHz EPYC processors. All DFT calculations were done in 2.60 GHz Xeon
processors using upto 128 Gb memory, while MD calculations were done in 2.90 GHz
EPYC processors using upto 32 Gb memory.
C.2 Synthesis
Synthetic procedures for the synthesis of N-(2’-hydroxyethyl)-carbazole was used
without modifications as reported in the literature.
1
Allyl methacrylate was freshly distilled
from CaH2 and was stored over 4A sieves. Carbazole was freshly recrystallized from 200
proof ethanol.
Synthesis of compound 9-(2-bromoethyl)-9H-carbazole) (2)
An oven dried three-neck flask was vacuum backfilled three times and charged with
2.00 g of 1 (9.47 mmol, 1.00 eq.) and 3.72 g triphenylphosphine (14.20 mmol, 1.50 eq.).
15 mL dry THF were added, and the mixture was cooled to 0 °C. In a separate flask 3.42
g carbon tetrabromide (11.83 mmol, 1.15 eq.) were dissolved in another 15 mL of dry THF
and this mixture was added dropwise at 0 °C to the first flask. The resulting mixture was
stirred at 0 °C for another 2 hours and then warmed up to room temperature overnight.
193

upon removal of the solvent in vacuo, the residue was redissolved in 50 mL DCM, washed
with 1 M NaOH(aq.) (1 × 100 mL) and water (2 × 100 mL), dried over MgSO4, filtered and
concentrated in vacuo. The crude product was purified via column chromatography
(100% hexanes) to afford the desired product as a white, crystalline solid in 83% yield
(2.146 g).
Synthesis of compound S-(2-(9H-carbazol-9-yl)ethyl)-ethanthioate (3)
An oven dried three-neck flask was vacuum backfilled three times and charged with
450.0 mg potassium thioacetate (3.94 mmol, 1.00 eq.) and 2.15 g of 2 (7.88 mmol, 2.00
eq.). 10 mL of dry THF and finally 38.33 mg of tetrabutylammonium chloride (0.138
mmol, 0.035 eq.) were added and the mixture was heated to 75 °C overnight. Upon cooling
to room temperature, the solids were filtered off and washed with ethyl acetate. The filtrate
was concentrated and purified by column chromatography (DCM/Hexanes = 1:1) to yield
the desired product as a white solid in 98% yield (1.039 g).

194

Synthesis of compound 2-(9H-carbazol-9-yl)ethanethiol (4)
An oven dried three-neck flask was vacuum backfilled three times and charged with
1.00 g of 3 (3.71 mmol, 1.00 eq.). Then 30 mL of ethanol were added. 445.46 mg of sodium
hydroxide (11.14 mmol, 3.00 eq.) were dissolved in 10 mL water and the resulting aqueous
solution was added dropwise to the flask at room temperature. The mixture was then heated
to 85 °C overnight. Upon cooling to room temperature, the mixture was neutralized to pH
= 7 by addition of 1 M HCl(aq.), extracted with ethyl acetate (3 × 50 mL), dried over MgSO4,
filtered and concentrated in vacuo. The crude product was purified by column
chromatography (DCM/Hexanes = 2:8) to yield the desired product as a white solid in 70%
yield (589.4 mg).

195

Synthesis of isotactic polymer 6

An oven dried Schlenk-flask was flame-dried three times and charged with 10 mL
dry toluene. Dropwise 0.045 mL 1,1-diphenylethylene (45.06 mg, 0.25 mmol, 0.025 eq.)
and 0.156 mL 1.6 M n-butyllithium in hexane (16.02 mg, 0.25 mmol, 0.025 eq.) were added
at room temperature and the mixture was stirred for 90 min to allow formation of the
initiator. Upon cooling to -78 °C, 1.345 mL allyl-methacrylate (1.26 g, 10.0 mmol, 1.00
eq.) were added dropwise and the resulting mixture was stirred at -78 °C for 6 hours. The
reaction was then quenched by addition of 1 mL of methanol and concentrated under
reduced pressure. The resulting residue was redissolved in chloroform, precipitated into
100 mL cold methanol, filtered and dried under high vacuum yielding the desired polymer
as a white fibrous solid in 75% yield (0.947 g).

196

Synthesis of syndiotactic polymer 7

An oven dried Schlenk-flask was flame-dried three times and charged with 50 mL
dry THF. Dropwise 0.045 mL 1,1-diphenylethylene (45.06 mg, 0.25 mmol, 0.025 eq.) and
0.156 mL 1.6 M n-butyllithium in hexane (16.02 mg, 0.25 mmol, 0.025 eq.) were added at
room temperature and the mixture was stirred for 90 min to allow formation of the initiator.
Upon cooling to -98 °C, 1.345 mL allyl-methacrylate (1.26 g, 10.0 mmol, 1.00 eq.) were
added dropwise and the resulting mixture was stirred at -98 °C for 5 hours. The reaction
was then quenched by addition of 1 mL of methanol and concentrated under reduced
pressure. The resulting residue was redissolved in chloroform, precipitated into 100 mL
cold methanol, filtered and dried under high vacuum yielding the desired polymer as a
white fibrous solid in 90% yield (1.13 g).

197

Synthesis of syndiotactic polymer 8

An oven dried Schlenk-flask was flame-dried three times and charged with 10 mL dry
THF. Dropwise 0.045 mL 1,1-diphenylethylene (45.06 mg, 0.25 mmol, 0.025 eq.) and
0.156 mL 1.6 M n-butyllithium in hexane (16.02 mg, 0.25 mmol, 0.025 eq.) were added at
room temperature and the mixture was stirred for 90 min to allow formation of the initiator.
Upon cooling to -98 °C, 0.673 mL allyl-methacrylate (630.0 mg, 5.0 mmol, 1.00 eq.) were
added dropwise and the resulting mixture was stirred at -98 °C for 5 hours. The reaction
was then quenched by addition of 1 mL of methanol and concentrated under reduced
pressure. The resulting residue was redissolved in chloroform, precipitated into 100 mL
cold methanol, filtered and dried under high vacuum yielding the desired polymer as a
white fibrous solid in 85% yield (0.532 g).

198

Synthesis of atactic polymer 9

An oven dried Schlenk-flask was flame-dried three times and charged with 10 mL dry
DMA, followed by 10 mL dry Toluene. 46.56 mg of CPDB (0.167 mmol, 0.0167 eq.) was
added, followed by 6.90 mg of AIBN (0.042 mmol, 0.0042 eq.). Mixture was stirred at
room temperature for 30 min until all the solid gets dissolved in solvent. 1.345 mL allyl-
methacrylate (1.26 g, 10.0 mmol, 1.00 eq.) were added dropwise and the resulting mixture
was stirred at 65 °C for 96 hours. The reaction was then quenched by addition of 1 mL of
methanol and concentrated under reduced pressure. The resulting residue was redissolved
in chloroform, precipitated into 100 mL cold methanol, filtered and dried under high
vacuum yielding the desired polymer as a light pink fibrous solid in 55% yield (0.693 g).

199

General method for synthesis of polymers (6a – 9a)
Synthesis was adapted from the literature with slight modification.
2
An oven dried
Schlenk-flask was flame-dried three times and charged with N2. 100 mg of polymer (6 –
9) (1 eq) was added to the flask followed by 1.5 eq of compound 4, 0.5 eq of DMPA and 5
mL of dry toluene. The mixture was stirred for 10 mins until all the solid gets dissolved.
The flask was cycled three times with Freeze-Pump-Thaw technique before the resulting
mixture was stirred at room temperature for 6 hours under 300 nm UV LED lamp. The
reaction was then quenched by addition of 1 mL of methanol and concentrated under
reduced pressure. The resulting residue was dissolved in chloroform, precipitate twice into
250 mL cold methanol, filtered and dried under high vacuum yielding the desired polymer
as a white amorphous solid.

200

C.3 NMR Spectroscopy

Figure C.1
1
H NMR of compound 2.

Figure C.2
1
H NMR of compound 3.

201

Figure C.3
1
H NMR of compound 4.

Figure C.4
1
H NMR of polymer 6.

202

Figure C.5
1
H NMR of polymer 7.

Figure C.6
1
H NMR of polymer 8.

203

Figure C.7
1
H NMR of polymer 9.

Figure C.8
13
C NMR of polymer 6.
204

Figure C.9
13
C NMR of polymer 7.

Figure C.10
13
C NMR of polymer 8.
205

Figure C.11
13
C NMR of polymer 9.

Figure C.12 Sample calculation of triad tacticity from
1
H NMR for polymer 6.
206

Figure C.13 Sample calculation of pentad tacticity from
13
C NMR for polymer 6.

Figure C.14
1
H NMR for polymer 6a.
207

Figure C.15
1
H NMR for polymer 7a.

Figure C.16
1
H NMR for polymer 8a.
208

Figure C.17
1
H NMR for polymer 9a.
C.4 Thermal Gravimetric Analysis (TGA)

Figure C.18 TGA plots of PCzETPMA polymers.

209

C.5 UV -Vis Spectroscopy

Figure C.19 As cast thin films of polymers 6a – 9a.

Figure C.20 Annealed thin films of polymers 6a – 9a.
210

C.6 X-Ray Diffraction

Figure C.21 As cast thin films of polymers 6a – 9a.

Figure C.22 Annealed thin films of polymers 6a – 9a.
211

C.7 Differential Scanning calorimetry (DSC)

Figure C.23 DSC scan of polymer 6.

Figure C.24 DSC scan of polymer 7.

212

Figure C.25 DSC scan of polymer 8.

Figure C.26 DSC scan of polymer 9.

213

Figure C.27 DSC scan of polymer 6a.

Figure C.28 DSC scan of polymer 7a.
214

Figure C.29 DSC scan of polymer 8a.

Figure C.30 DSC scan of polymer 9a.

215

C.8 Hole Mobilities

Figure C.31 Polymer 6a with different annealing conditions.

Figure C.32 Polymer 7a with different annealing conditions.
216

Figure C.33 Polymer 8a with different annealing conditions.

Figure C.34 Polymer 9a with different annealing conditions.

217

C.9 Atomic Force Microscopy (AFM)

Figure C.35 Polymers 6a topology image.

Figure C.36 Polymers 7a topology image.
218

Figure C.37 Polymers 8a topology image.

Figure C.38 Polymers 9a topology image.

219

C.10 Cyclic Voltammetry

Figure C.39 CV scan of polymer 6a.

Figure C.40 CV scan of polymer 7a.
220

Figure C.41 CV scan of polymer 8a.

Figure C.42 CV scan of polymer 9a.

221

Table C.1 Electrochemical HOMO values for polymer 6a – 9a
Polymer Onset voltage [V] HOMO energy [eV]
Isotactic polymer 6a 0.52 5.62
Syndiotactic polymer 7a 0.59 5.69
Syndiotactic polymer 8a 0.57 5.67
Atactic polymer 9a 0.57 5.67

C.11 Simulations.
Using IQmol molecular builder, an initial starting conformation was developed for
atactic, syndiotactic and isotactic PCzETPMA polymers. These polymer chains were
limited to 20 repeating units (<1000 atoms), because of computational limitations. Within
IQmol itself, once the initial conformation was made, the initial structure was optimized
using Molecular Mechanics and MMFF94 force field. Once energy optimization was done,
using IQmol, a Q-Chem input file was created for geometry optimization using Hartree-
Fock (HF) theory and the STO-6G basis set. Then the optimized geometry from HF/STO-
6G was taken and loaded into IQmol and another Q-Chem input file was created for
geometry optimization using DFT (B3LYP) and 6-31+G(d) basis set to obtain our final
optimized polymer chains. It took approximately 18-24 days to complete the geometry
optimization for the polymer chains with 20 repeating units.
Once these structures were optimized using Q-Chem, these structures are uploaded
to Automated Topology Builder (ATB) and Repository (Version 3.0),
3
to get the necessary
topology files for molecular dynamics (MD) calculations. Generally, these topology files
contain all the different kinds of atoms present in the system, their masses, different bonds,
bond angles, bond dihedrals and improper dihedrals within the molecule to maintain the
connectivity of the atoms and avoiding formation of new bonds during MD simulations.
222

These topology files were built using GROMOS_54A7 force field and were downloaded
directly from the ATB Repository. Using these topology files and force field files, a 3D
MD simulation box of 200 Å was created with periodic boundary conditions and was
packed with 64 chains of the polymer using moltemplate. Moltemplate helps to create a
database of all the necessary details needed for MD calculations
using LAMMPS.
Each chain of polymer was then permitted to relax within the MD simulation for 1
ns in isolation at 0 K in vacuum using the LAMMPS suite, according to the intramolecular
components of the GROMOS_54A7 force field. Then each chain was again permitted to
relax within the MD simulation for 1 ns in isolation at 300 K using the same LAMMPS
suite mimicking their behavior in solution as shown above. After that, this large simulation
volume was then compressed over a period of 40 ps at 300 K until the density of average
1.2 g/mL was reached, hence mimicking spin coating of the solution into a thin film. After
that, pressure was equilibrated to atmospheric pressure at constant volume and temperature
with timesteps of 4 fs using the LAMMPS suite.
To study the effect of thermal annealing, the, the same calculation methodology
was applied with slight variation. Once the density of 1.2 g/mL was reached, the
morphology was subjected with varying temperature, where temperature was increased
from 300 K to 500 K over 4 ns period, then the annealed films were again finally cooled
down to 300 K over a further 4 ns period, before equilibrating at 300 K and atmospheric
pressure for a final of 4 ns.
223

Figure C.43 Optimized structure for atactic polymer with 20 repeating units.

Figure C.44 Optimized structure for atactic polymer with 40 repeating units.

224

Figure C.45 Optimized structure for isotactic polymer with 20 repeating units.

Figure C.46 Optimized structure for isotactic polymer with 40 repeating units.
225

Figure C.47 Optimized structure for isotactic polymer with 20 repeating units.

Figure C.48 Optimized structure for isotactic polymer with 40 repeating units.
226

Figure C.49 Thin layer MD structure for atactic polymer at room-temp.

Figure C.50 Thin layer MD structure for atactic polymer at room-temp where all the
carbazole moieties are highlighted.
227

Figure C.51 Thin layer MD structure for atactic polymer after annealing.

Figure C.52 Thin layer MD structure for atactic polymer after annealing where all the
carbazole moieties are highlighted.

228

Figure C.53 Thin layer MD structure for isotactic polymer at room-temp.

Figure C.54 Thin layer MD structure for isotactic polymer at room-temp where all the
carbazole moieties are highlighted.
229

Figure C.55 Thin layer MD structure for isotactic polymer after annealing.

Figure C.56 Thin layer MD structure for isotactic polymer after annealing where all the
carbazole moieties are highlighted.
230

Figure C.57 Thin layer MD structure for syndiotactic polymer at room-temp.

Figure C.58 Thin layer MD structure for syndiotactic polymer at room-temp where all
the carbazole moieties are highlighted.
231

Figure C.59 Thin layer MD structure for syndiotactic polymer after annealing.

Figure C.60 Thin layer MD structure for syndiotactic polymer after annealing where all
the carbazole moieties are highlighted.

232

C.12 References
(1) Farah, A. A.; Pietro, W. J. Synthesis and Characterization of Multifunctional
Polymers via Atom Transfer Radical Polymerization OfN-(Ω′-Alkylcarbazolyl)
Methacrylates Initiated by Ru(II) Polypyridyl Chromophores. J. Polym. Sci. Part A
Polym. Chem. 2005, 43 (23), 6057–6072. https://doi.org/10.1002/pola.21027.
(2) Roy, D.; Ghosn, B.; Song, E. H.; Ratner, D. M.; Stayton, P. S. Polymer-
Trimannoside Conjugates via a Combination of RAFT and Thiol-Ene Chemistry. Polym.
Chem. 2013, 4 (4), 1153–1160. https://doi.org/10.1039/c2py20820b.
(3) Malde, A. K.; Zuo, L.; Breeze, M.; Stroet, M.; Poger, D.; Nair, P. C.;
Oostenbrink, C.; Mark, A. E. An Automated Force Field Topology Builder (ATB) and
Repository: Version 1.0. J. Chem. Theory Comput. 2011, 7 (12), 4026–4037.
https://doi.org/10.1021/ct200196m.

Abstract (if available)

Abstract Conjugated polymers (CPs) are widely explored for 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. However, despite outstanding performance in optoelectronic applications, CPs nonetheless are limited by several challenges. CPs have low solubility, low environment stability, restricted mechanical properties, and limited synthetic methods. In the search for alternatives to CPs, non-conjugated pendant electroactive polymers (NCPEPs) possess a great deal of potential for improving the physical and mechanical properties of semiconducting polymers while retaining the optical and electronic properties for optoelectronic applications. NCPEPs also offer access to a broad range of controlled polymerization techniques for non-conjugated polymers that promise access to highly tailored structures with diverse architectures. Despite the potential advantages of NCPEPs, charge carrier mobilities are typically several orders of magnitude lower than CPs, likely due to significant disorder and limited π-π stacking. In this dissertation, strategies for improving the charge carrier mobility of NCPEPs are provided through the alteration of structural parameters of the polymers, such as stereoregularity, spacer length, and the polymer backbone. Along with the structural parameters, new polymerization techniques are also explored to synthesize functional NCPEPs with improved charge carrier mobilities.

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Creator Samal, Sanket (author)

Core Title Non-conjugated pendant electroactive polymers as potential materials for opto-electronic applications

School College of Letters, Arts and Sciences

Degree Doctor of Philosophy

Degree Program Chemistry

Degree Conferral Date 2021-12

Publication Date 12/17/2021

Defense Date 11/11/2021

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag OAI-PMH Harvest,optoelectronics,pendant,polymers

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Advisor Thompson, Barry (committee chair), Brutchey, Richard (committee member), Gupta, Malancha (committee member)

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