Beyond Polythiophenes: Exploring the Impact of Precisely Controlled Microstructure of Group 16 Conjugated Polymers on their Supramolecular Organization and Properties

Well-defined, regio-regular conjugated polymers such as P3HT have been extensively explored over the past few decades for applications in the field of organic electronics. Methods to explore the microstructure of this benchmark material (such as atomic force microscopy (AFM) and X-ray scattering techniques (i.e. grazing incidence X-ray scattering (GIWAXS)) have enabled the scientific community to discern how atomic-scale periodicity and nanoscale organization can influence the polymer’s physical properties such as its thermal, photo and electronic response. The development of novel conjugated polymers with various heteroatom sequence and side-chain architecture is of particular interest as a way to tune the physical properties and enhance
photo-stability in light and air. Correlation between polymer microstructure and the resulting macroscopic properties is paramount to develop next generation materials. Therefore, the scope of this work entails an overview of conjugated polymers (Chapter 1) with insights to examining
structure-property relationships of Group 16 family homopolymers (Chapter 2), including a ‘model’ fitting of solid-state UV-vis spectra inspired by Spano and co-workers. Beyond polythiophenes, assessment of periodic and random copolymers with similar composition of thiophene and selenophene units (Chapter 3) revealed that regular placement of selenophene improved polymer organization with enhanced charge delocalization (characterized by ‘model’ fitting of UV-vis spectra). And finally, ester side-chain substitution in polyfurans not
only showed improved photo-stability in the presence of light and air (Chapter 4), but also favored an all-cis conformation resulting in a helical packing arrangement. This favored conformational structure was also shown to extend to alternating copolymers containing ester substituted furan
rings. In contrast, ester substituted polythiophene exhibited extended configurations with higher degrees of disorder. In the alternating copolymer, the placement of ester groups along the polymer backbone, resulted in the low band-gap structures.