Tuning side chains to affect phase behavior and charge mobilities of PCPDTBT donor-acceptor conjugated polymers

Elucidating the critical components of molecular design would accelerate the implementation of conjugated polymers for electronic and energy applications. Using a donor-acceptor alternating copolymer based on a polycyclopentadithiophene benzothiadiazole backbone (PCPDTBT), we modify side chains to perturb phase behavior and charge mobilities in organic field-effect transistors. We use both branched and linear side chains of varying length and observe changes in glass transition temperatures, melting temperatures and liquid crystalline clearing temperatures using a combination of calorimetry, rheology, and X-ray scattering. Fabricating and testing field-effect transistors with PCPDTBT as the active layer yield field-effect mobilities that depend on the side chain substituent. Optimizing side chain composition and architecture is likely crucial to achieve remarkable charge mobilities of 10 cm^2/Vs that is observed with devices based on PCPDTBT.