Benzodithiophene homopolymers via direct (hetero)arylation polymerization

Abstract

Direct (hetero)arylation polymerization (DHAP) of a monobrominated benzo[1,2-b:4,5-b′]dithiophene monomer using the Herrmann–Beller catalyst with a tertiary phosphine provided benzodithiophene homopolymers in good yields. Employing both P(o-OMePh)3 and P(o-NMe2Ph)3 as the phosphine ligands gave well-defined polymers—with the later phosphine providing a higher molecular weight polymer. The preparation of a benzodithiophene (BDT) trimer was used to assist in the assignment of the 1H NMR spectra of the synthesized polymers which show largely defect-free couplings. The optical spectra of polymers formed via DHAP and those prepared using traditional Stille couplings are essentially identical, which further confirms the presence of well-defined BDT–BDT couplings along the conjugated polymer chain. These results confirm that carboxylic acid additives are not always necessary to suppress defects in DHAP polymerizations and that DHAP is a viable alternative to traditional Stille coupling for the preparation of benzodithiophene homopolymers.