Syntheses of Gradient π-Conjugated Copolymers of Thiophene

A study was conducted to demonstrate syntheses of gradient π-conjugated copolymers of thiophene. Thiophene-based monomers were selected because the cross-propagation can readily occurred between these monomers. The two monomers were prepared in situ by magnesium-halogen exchange using a mixed halogen precursor to regioselectively generate the Grignard reagents. All copolymerizations were run at 0 °C to prevent monomer decomposition via reaction with i-PrI generated in the metathesis reaction. A linear increase in the number-average molecular weight as a function of conversion was observed, consistent with a chain-growth mechanism when Ni(dppe)Cl2 and Ni(dppp)Cl2 were used as initiators. A series of batch polymerizations were also performed, wherein the initial molar ratio of 1:2 was varied, forming copolymers with different final compositions.