Evidence for the chain-growth synthesis of statistical π-conjugated donor-acceptor copolymers

The synthesis of a series of dithienosilole-benzotriazole donor-acceptor statistical copolymers with various donor-acceptor ratios is reported, prepared by Kumada catalyst-transfer polymerization. Statistical copolymer structure is verified by (1) H NMR and optical absorption spectroscopy, and supported by density functional theory (DFT) calculations. The copolymers exhibit a single optical absorption band that lies between dithienosilole and benzotriazole homopolymers, which shifts with varying donor-acceptor content. A chain extension experiment using a partially consumed benzotriazole solution as a macroinitiator followed by addition of dithienosilole leads to the synthesis of a statistical dithienosilole-benzotriazole block copolymer from a pure benzotriazole block, demonstrating that both chain extension and simultaneous monomer incorporation are possible using this methodology.