A Close Look at the Phase Behavior of Polymer Semiconductors Using Fast Calorimetry
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Weber, Mark
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Abstract
Conjugated polymers have emerged as a promising class of semiconductor materials, thanks to their tunability and mechanical flexibility, among other desirable properties. Over the years, polymer semiconductors have made significant strides in applications like photovoltaics. However, these advancements often stem more from the vast array of organic moieties available to chemists than from a deep understanding of structure-property relationships. Instead of focusing on refining existing material systems, many innovations arise from novel chemical structures, which further complicates our grasp of these critical relationships.
The goal of this thesis is to establish new structure-property relationships for conjugated polymer semiconductors. Chapter 1 provides background information and motivation, introducing the implementation of fast scanning calorimetry and concluding with an outline of the thesis scope. Chapter 2 builds on this foundation by detailing the characterization methodologies and relevant material information. In Chapter 3, we apply fast scanning calorimetry to study both single-phase and two-phase commodity polymers, developing a protocol to track and quantify phase transition temperatures. This methodology is extended in Chapter 4 to semiflexible poly(3-hexylthiophene) (P3HT) derivatives, where heteroatom substitution is used to increase backbone rigidity and promote chain-extended structures. Chapter 5 continues this progression by further enhancing backbone rigidity and planarity, introducing the sanidic-like class of polymers, distinguished by their extended sidechains and ribbon-like morphology. The thesis concludes in Chapter 6 with a summary of key findings and an outlook on future research directions. Additional supporting data and discussion are presented in the appendix. Collectively, the insights from these studies aim to inform new design principles by highlighting the roles of backbone rigidity and sidechain ordering in the performance of polymer semiconductors.
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2025-12
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Dissertation (PhD)