Diketopyrrolopyrrole-Based Low-Bandgap Conjugated Polymers with Siloxane Side Chains for Electrochromic Applications

Abstract

A series of conjugated copolymers P1–P3 were synthesized from 3,6-bis(5-bromothiophen-2-yl)-2,5-bis(6-(1,1,1,3,5,5,5-heptamethyltrisiloxan-3-yl)hexyl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione and 2,5-bis(trimethylstannyl)-3,4-dialkoxythiophene or its analogue via Stille coupling reactions, with molecular weights in the range of 13000–18000 g mol–1 and polydispersity indexes of 1.4–1.7. This new type of donor–acceptor polymers demonstrated reasonable switching speed, promising redox stability, together with high optical contrast and coloration efficiency. Although, at the current stage, the hybrid siloxane-terminated side chain did not significantly improve the overall performance of the resultant polymers, the unique chemical properties of the siloxane group would offer possibilities for crosslink after suitable post-polymerization treatment, and thus pave the way for future fine-tuning of the morphology of electrochromic films.