Thienoisoindigo-based donor-acceptor random copolymers: synthesis, characterization, and thin film nanostructure study

Donor-acceptor (D-A) random copolymers containing thienoisoindigo (TIG), diketopyrrolopyrrole (DPP), and benzothiadiazole (BT) acceptor units (Pa1-5 with TIG/DPP acceptor units, and Pb1-5 with TIG/BT acceptor units) have been developed. The typical Stille cross-coupling polymerization afforded D-A random copolymers with various acceptor compositions by adjusting monomer feed ratios. The obtained polymers exhibited the excellent light absorption by utilizing intramolecular charge transfer between donor and acceptor units. In particular, one of random copolymers with TIG/BT acceptor units (Pb2) accomplished the wide-range absorption in the range of 300-1400 nm in the thin film state. In the cyclic voltammetry analysis, the HOMO levels of polymers were successfully tunable in the wide range of - 4.86 to - 5.25 eV. The obtained results demonstrated that the D-A random copolymer could be a promising design for tailored and wide tuning of polymer properties, leading to the development of conjugated polymeric materials and their optoelectrical applications.