Synthesis of alternating conjugated copolymers from direct C-H arylation

Abstract

Synthesis of conjugated polymers via Direct Hetero Arylation Polycondensations (DHAPs) through palladium catalyzed cross-coupling polymerization was investigated. This synthetic method has advantages over traditional method by omitting the preactivation of one of the coupling partner, minimizing production of toxic wastes, side products, and cost. We obtained the donor-acceptor copolymer 4 from DHAPs of 2,5-dichloro-3,4-dinitrothiophene (DCDNT) and 3,4-ethylenedioxythiophene (EDOT) as orange solid in 31.7% yield. Copolymer 5 was also obtained using the same methodology from EDOT and 1,4-dibromo-2,5-bis(octyloxy)benzene (DBOB) as the precursors, in which the best result was 86% yield. The optimized DHAP condition was used to prepare copolymers 6 (from 3-hexylthiophene and DBOB), 7 (from dibromooctyltriazole and EDOT) and 8 (from octylbenzotriazole and EDOT) in 65.4%, 83.2%, and 77.2% yields, respectively. These conjugated copolymers exhibited UV-visible maximum wavelength absorption at various values in the range of 300-451 nm.