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theses

π-Conjugated (co)polymers are an important class of organic semiconducting materials for (opto)electronic device applications such as organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs), and organic solar cells. The semiconducting capabilities of these materials are a result of π-electron delocalization along the (co)polymer backbone. In additional to their desirable electrical and optical properties, these materials must also exhibit atmospheric stability and solution processability, hence polyenes such as polyacetylene have no commercial viability despite their high electrical conductivity. Therefore, polyaromatics are the preferred materials despite resonance effects that confine π-electrons to individual aromatic scaffolds and inhibit optimal charge-carrier delocalization along the polymer chain. Recently, there has been interest in preparing π-conjugated polymers that feature both the favorable conjugation lengths typical of polyenes (e.g., polyacetylene) and the atmospheric stability and processability typical of polyaromatics (e.g., polythiophene). Unfortunately, there remains a synthetic challenge to prepare non-aromatic π-conjugated precursors that can be readily incorporated into π-conjugated polymeric systems. The work described herein addresses this challenge by investigating the viability of using 5,5-dimethylcyclopentadiene as a non-aromatic building block with the topology of common aromatics such as thiophene, furan, and pyrrole. Specifically, a series of cyclopentadiene-containing (macro)molecules were prepared by Suzuki-Miyaura cross-coupling reaction and their structural, spectroscopic, and electrochemical properties characterized by 1 H NMR, single crystal X-ray crystallography, cyclic voltammetry, and/or UV/vis absorption and fluorescence spectroscopies. The results of our investigation show that the cyclopentadiene moiety tends to reduce optical band-gap and onset oxidation potentials in the majority of systems studied here. Moreover, OLEDs and OFETs devices employing Cp-containing (macro)molecules have been prepared in collaboration with the Carroll and Heeney groups at Wake Forest University and Imperial College-London respectively. To the best of our knowledge, these are the first examples of (opto)electronic devices employing cyclopentadiene-based π-conjugated materials.

ETD_7441

Ph.D.

Includes bibliographical references

by Lei Chen

doi:10.7282/T3ZG6VM9

ETD doctoral

The author owns the copyright to this work.