Synthesis of conjugated polymers via an exclusive direct-arylation coupling reaction: a facile and straightforward way to synthesize thiophene-flanked benzothiadiazole derivatives and their copolymers

Abstract

Thiophene-flanked benzothiadiazole derivatives (DTBTs) have been among the most widely used building blocks for the synthesis of a myriad of high-performance conjugated polymers for applications in optoelectronic devices, sensing and bioimaging. We first report that these building blocks could be synthesized via a facile and straightforward method called direct arylation coupling. Our optimization of Pd₂dba₃-catalyzed direct arylation coupling gave DTBTs with a comparable yield to that of the Suzuki or Stille coupling reaction. DTBTs were further polymerized with fluorene dibromide via direct arylation polycondensation to give well-defined alternating copolymers. One-pot direct arylation polymerizations were also carried out between benzothiadiazole dibromide, fluorene dibromide and thiophene derivatives, to form DTBT-containing random copolymers. These random copolymers showed typical multichromophore characteristics. The differences in optical properties between the alternating copolymers and random copolymers were evaluated.