Direct arylation polycondensation as conjugated polymer synthesis methodology

Direct arylation polymerization (DArP), which is a cross-coupling polymerization between a dihaloarene monomer and a non-substituted arene monomer, has attracted widespread attention for conjugated polymer synthesis. In DArP, no prior preparation of arene monomers with organometallic functionalities is necessary, in contrast to typical cross-coupling polymerizations such as the Suzuki and Stille reactions. Furthermore, the low toxicity of the byproducts of DArP contributes to green chemistry. In terms of efficiency and environmental friendliness, these advantages make DArP an attractive next-generation polymer synthetic method. To date, numerous conjugated polymers have been synthesized by DArP. However, many problems remain to be overcome, including better understanding of the correlation between polymer structure and DArP factors, the design of a more efficient DArP system, and so on. Addressing these problems could lead to the establishment of DArP as a viable alternative for conjugated polymer synthesis. We revealed that a variety of conjugated polymers such as donor-acceptor alternating copolymers (arylene diimide-based donor-acceptor alternating copolymers and thienoisoindigo-based donor-acceptor alternating copolymers) and regioregular poly(3-alkylselenophene)s were successfully synthesized by the DArP strategy based on appropriate molecular design and adjustment of the catalytic system. This focus review will describe our recent studies developing the synthesis of novel conjugated polymers via DArP.