Synthesis of comonomer possessing 4,4'-dinonyl-2,2'-bithiazole and 3-phenylthieno[3,2-b] thiophene units (PhTT-NBT-PhTT) was performed under Stille cross coupling condition. Its electropolymerization was conducted in the presence of trifluroborate-diethyl ether (BF3 center dot DEE) to lower the electrochemical polymerization potential through a complex formation between heteroaromatic monomers and boron trifluoride. Electrochemical properties of obtained P[PhTT] and P[PhTT-NBT-PhTT] films, such as effect of electrolyte, polymerization charge, potential limits on the redox behaviour were investigated. They were further characterized by UV-visible spectrophotometric measurements. Corresponding electrical equivalent circuit was applied to the experimental electrochemical impedance spectroscopy (EIS) data to explain the parameters of each element and the interface between the Pt/P[PhTT]/BF3 center dot DEE and Pt/P[PhTT-NBT-PhTT]/BF3 center dot DEE systems. The band gap of P[PhTT-NBT-PhTT was obtained as 2.04 eV by insitu spectroelectrochemical measurements. Frontier molecular orbitals and electropolymerization of the comonomer were assessed computationally. (C) 2016 Elsevier Ltd. All rights reserved.