Controlling conjugated polymer morphology and charge carrier transport with a flexible-linker approach†
The Stille-coupling polymerization of a short conjugated polymer with an aliphatic linker was used to demonstrate a prototype in a new class of polymer semiconductors wherein the conjugation segment length and the length of the entire chain can be independently controlled. Subsequent thermal, morphological, and 2D grazing-incidence crystallographic analysis revealed this prototype polymer's ability to exhibit distinct thin-film morphologies without changing the molecular weight. In field-effect transistors this unique ability gave rise to an improvement of the charge carrier mobility from fibril-type (0.01 cm2 V−1 s−1) to terrace morphologies (0.04 cm2 V−1 s−1). When compared to a fully-conjugated, high molecular weight polymer, these differences afforded insight into the roles of inter- and intra-molecular charge transport in the film, highlighting the importance of chain self-assembly on charge transport. Overall, our results indicate that employing linkers is a promising route to advance morphology control in semiconducting polymer based devices.