Synthesis and characterization of π-conjugated polymers based on 2-arylbenzimidazole and 4,7-di-thiophene-2-yl-4,5,6,7-tetrahydro-benzo[1,2,5] thiadiazole

A newly designed 2-arylbenzimidazole derivative which plays a role of co-acceptor unit has been prepared for the synthesis of conjugated polymer. 2-arylbenzimidazole derivative has been incorporated into 4,7-dithiophen-2-yl- benzo(2,1,3)thiadiazole (TBT) and fluorene based alternating copolymers with different ratios of 5 mol.% and 10 mol.% named POFTBT-IMD5, POFTBT-IMD10, respectively. We also synthesized alternating copolymer of 9,9-dioctylfluorene and TBT (POFTBT) to compare physical properties. POFTBT-IMD5, POFTBT-IMD10 films showed absorption peaks at 559 and 555 nm, respectively. The HOMO and LUMO energy levels of POFTBT-IMD5, POFTBT-IMD10 were-5.4/-3.84 eV and-5.4/-3.81 eV, respectively, which were similar to those of POFTBT (-5.3/-3.7 eV).