Processing components in π-conjugated polymers: Controlling solubility, morphology, and functionality through structural design
Schmatz, Brian J.
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Over the past 30 years conjugated polymers have demonstrated performance strides in solution-printed photovoltaics, transistors, displays, and sensors. With fundamental structure-property relationships in place, the next step is to prepare these materials for use in large-scale, high-throughput printing facilities where reproducibility, tolerance to the environment, safety, and sustainability will all play a pivotal role in the ultimate success of conjugated polymer based electronics. This dissertation explores how to achieve that next step through the use of processing components, or structural moieties that embed a desired processing property. Chapter 1 provides an introduction to the design, fundamental properties, and methods of processing soluble conjugated polymers, placing specific emphasis on the interplay between molecular structure, processability, and ultimately performance. Polymer synthesis, characterization, and processing methodology unique to this dissertation are presented in detail in Chapter 2. Chapter 3 describes the use of triphenylamine as a processing comonomer in dioxythiophene polymers. The triphenylamine comonomer templates an amorphous thin-film morphology by embedding backbone torsion and conjugation breaks, providing reproducible films that are tolerant to fluctuations in processing conditions. Chapter 4 explores the use of polymer side chains with multiple functionalities, or multistage side chains, to control solubility for aqueous printable conjugated polymers. Finally, Chapter 5 delves into the intricate morphological effects of polymer side chain placement in organic photovoltaic donor-acceptor blends. Specifically, the study utilizes a novel family of donor-acceptor polymers with methylated acceptor monomers to observe how side chain steric interactions affect morphology and optoelectronic properties in blends of polymeric donors and molecular acceptors.