(29e) The Interplay Morphology and Sequence on Ion-Coupled Electron Transport in Mixed Conducting Polymers

Macromolecules that exhibit both electron transport and ionic mass transport (i.e., mixed conducting polymers) are ascendant with respect to both emerging application spaces and the elucidation of their fundamental physical principles. The unique coupling between the two modes of conduction puts these materials at the center of many next-generation organic electronic applications, including organic electrochemical transistors. However, the degree to which ion motion is coupled with electron transport and morphology changes, and the range of polymer chemistries that can exhibit and be optimized for electrochemical response in aqueous media is unknown. To elucidate the general relationship between polymer structure, morphology, and mixed conduction we have developed a hybrid simulation methodology consisting of coarse-grained modeling of mixed conducting materials and master-equation modeling of electron transport to characterize long-timescale morphology reorganizations and its impact on mixed conduction. Using this method, we have performed a systematic study of several polymer design components, including side-chain placement and constitution, repeat unit sequence, and tailored π-π interactions to develop generic design rules for next-generation mixed conducting polymers. The results highlight the critical role of electron-ionic coupling in modulating the conduction of these materials and suggests the contemporary modular design paradigm of separately optimizing electron and ion conducting components leaves out this critical physics.