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^oC. 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.