Copolymerization of benzothiophene (BTh) with thiophene (Th) was successfully achieved electrochemically by potentiodynamic methods. BTh and Th were also both copolymerized separately with pyrrole (Py) for comparison. The electrochemical properties of copolymers obtained at different monomer concentrations, scan rates and scan numbers were characterized by voltametric, electrochemical impedance spectroscopy (EIS), ATR-FTIR, spectroelectrochemical and conductivity measurements. Results suggested that optical band gaps and oxidation potentials can be decreased by copolymerization and this advantage makes copolymers suitable for electrochromic and photovoltaic applications. Conductivity of copolymers generally lies in between that of homopolymers and specific capacitance value of BTh could be raised from 18.9 mF/cm(2) to 138.3 mF/cm(2) by copolymerization with Py. A proper mechanism for copolymerization was suggested. (C) 2012 Elsevier B.V. All rights reserved.