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Donor-Acceptor Methods for Band Gap Reduction in Conjugated Polymers: the Role of Electron Rich Donor Heterocycles

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Donor-Acceptor Methods for Band Gap Reduction in Conjugated Polymers: the Role of Electron Rich Donor Heterocycles DONOR-ACCEPTOR METHODS FOR BAND GAP REDUCTION IN CONJUGATED POLYMERS: THE ROLE OF ELECTRON RICH DONOR HETEROCYCLES By CHRISTOPHER A. THOMAS A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2002 Copyright 2002 by Christopher A. Thomas All rights reserved. ACKNOWLEDGMENTS I thank my parents, Nancy and Larry, for their continuous support and attempts to understand and encourage me during what has been simultaneously the most enjoyable and most stressful part of my life. They made this document possible by encouraging and par- ticipating in experiences that ensured I would have the backgound and interest in trying to figure out how the world works. The decision about whom to work for in graduate school is one of the events I have agonized the most about in my life. As promised, the graduate advisor-student relationship is a complicated entity consisting of advisor, boss, counselor and friend that can change its active role without warning. Despite this, I am positive that there is no other person that I would rather have worked with during this process. I especially appreciate being given an unusual amount of decision making and direction setting power in the projects I was involved with and the freedom to explore aspects of science that interested me even when they did not overlap cleanly with Professor Reynolds’ research interests or funding. For their major contributions to my enjoyment and interest in chemistry, I thank Joe Carolan for his contagious enthusiasm, and Joel Galanda, who immensely affected the three years of my life he was involved with my chemistry and physical science education. I especially appreciate his role in enabling my employment at the Rockwell International Science Center, one of the experiences I consider most valuable in my education. I thank my mentor at Rockwell, Les Warren, who, from high school through undergraduate and graduate school, has influenced my decisions on how to approach life, my education and iii career more than any other person I have met. To Tim Parker, thanks go for largely direct- ing my research experiences as an undergraduate and showing me how to do synthesis even after being hit by my snowboard. Several coworkers have had an important role both in this document and graduate school. Thanks go to Jacek Brzezinski and Kyukwan Zong for making the fluorenones and XDOPs respectively, allowing me to spend my time doing things I found to be more inter- esting. To Roberta Hickman, thanks go for friendship, helping me, for making lab-life more fun, and for your contributions to the data which eventually became Figure 5-5. Thanks go to C. J. Du Bois, the reigning Reynolds’ group lab clown, for the Yuengling-Tücher inspired conversations at the Copper Monkey and always finding the reference that I knew existed but could not find. I also appreciate the rest of the members of the Reynolds group, especially Carl Gaupp and Irina Schwendenman, for being helpful when I needed it and generally fun to be around. I also appreciate the help provided by Lori Clark, Donna Bal- colm, and Professor James Deyrup for assitance in navigating through the UF bureaucracy, Lorraine Williams for making life on the polymer floor easier and Khalil Abboud and Peter Steel who solved the crystal structures included in this document. Finally, my time here would not have been nearly as fun without the friends that provided the distractions necessary to have made this work possible to get through when it felt like work. Thanks go to Dominic Rice, who throws the best parties I have ever been to and was always up for hanging out when I needed to blow off steam; Kevin Boone for the football weekend fun and the good friends I have met through him; the KA’s for fun times tubing and at the lake house; Andrew Cottone, the Mobsters and the Bandits for the softball and baseball experiences; and Megan Odroniec for a fun couple of years. iv TABLE OF CONTENTS page ACKNOWLEDGMENTS ................................................................................................ iii ABSTRACT.......................................................................................................................vii CHAPTERS 1 BAND GAP: THE DEFINING QUANTITY FOR CONTROLLING THE PROPERTIES OF CONJUGATED POLYMERS .......................................................1 Brief History of Conjugated Polymers ...................................................................1 Origin of Bands and Conductivity in π-Conjugated Organic Materials .................4 Why Band Energies Are Important ......................................................................12 Conductivity Mechanisms in Organic Materials ..................................................15 Ionic Conductivity and Redox Conductivity ..................................................17 Polarons, Bipolarons and p-Dimers ................................................................20 Doping Induced Optical Transitions .....................................................................24 Conjugated Polymer Synthesis and Device Incorporation ...................................26 2 ELECTROCHEMICAL AND COUPLED IN SITU EXPERIMENTAL METHODS IN CONJUGATED POLYMER RESEARCH ................................................................36 Introduction ...........................................................................................................36 Monomer Crystallization ......................................................................................37 Spectroelectrochemistry ........................................................................................38 Colorimetry ...........................................................................................................43 Cells and Reference Electrodes for Electrochemistry ..........................................47 General Electrochemistry and Cyclic Voltammetry (CV) ....................................52 Differential Pulse Voltammetry (DPV) ................................................................61 In Situ Conductivity ..............................................................................................62 Four-Point Conductivity on Free-Standing Films ................................................69 Electrochemical Quartz Crystal Microbalance (EQCM) ......................................72 3 DONOR MEDIATED BAND GAP REDUCTION IN A HOMOLOGOUS SERIES OF CONJUGATED POLYMERS ..............................................................................76 Introduction and Literature Overview ..................................................................76 Synthesis and Monomer Properties ......................................................................81 v Monomer Structural Features and Crystallography ..............................................85 Computational Explanations of Monomer Properties ..........................................90 Polymer Optical Properties ...................................................................................93 Polymer Electrochemistry ...................................................................................106 Conclusions and Perspective ..............................................................................115 Experimental Section ..........................................................................................122 4 THE ROLE OF INTERGAP REDOX STATES IN CONJUGATED POLYMER REDUCTION PROCESSES: THIENYL AND EDOT CONTAINING FLUORENONES ......................................................................................................129 Introduction .........................................................................................................129 Monomer Synthesis and Properties ....................................................................133 PBEDOT-DCF and PBTh-DCF Synthesis, Electrochemistry and Spectroelectrochemistry ......................................................................................136 Monomer Electrochemistry ................................................................................148 Conclusions .........................................................................................................151 Experimental Section ..........................................................................................153 5 POLY(ALKYLENEDIOXYPYRROLES): AQUEOUS COMPATIBLE CONDUCTING POLYMERS WITH LOW FORMAL REDOX POTENTIALS ..160 Introduction .........................................................................................................160 Monomer Synthesis and Polymer Electrosynthesis ............................................165 Polymer Electrochemistry ...................................................................................169 Polymer Spectral Characteristics ........................................................................174 Electrochemical Quartz Crystal Microbalance Studies on Ion Transfer ............180 Conclusions .........................................................................................................184 Experimental Section ..........................................................................................184 APPENDIX A CRYSTALLOGRAPHIC INFORMATION FOR CYANOVINYLENE MONOMERS ...........................................................................................................188 B CRYSTALLOGRAPHIC INFORMATION FOR FLUORENONE MONOMERS ...........................................................................................................210
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