Synthesis and characterization of copolymers based on benzothiadizole-thiophene-phenylenevinylene

Two novel copolymers based on benzothiadizole-thiophene-phenylenevinylene have been synthesized through palladium catalyzed triple-bond polycondensation method. The copolymers exhibit good solubility in common organic solvents such as CHCl3, CH2Cl2 and THF. The structures and properties of the two copolymers are characterized by FT-IR, 1H-NMR, UV-Vis absorbance (Abs), gel permeation chromatography (GPC), thermal gravimetric analysis and cyclic voltammetry (CV). The copolymers of P1 and P2 show absorption spectra with maximum peak at 532 nm and 573 nm in solution, respectively. Compare to their monomers M1 and M2, the absorption peaks of P1 and P2 were red-shifted by 34 nm and 54 nm respectively. Thermal gravimetric analysis demonstrated that the polymers were stable and little weight loss was observed below 300°C. Cyclic voltammetry experiments showed that the band gaps of the copolymers were 1.81 eV and 1.62 eV, respectively, suggesting their potential for applications as organic solar cell materials.