An investigation of the electropolymerization of terthiophene in boron fluoride–ethyl ether

Various potentials have been used to oxidize terthiophene in boron fluoride–ethyl ether (BFEE), the final products are then studied by the surface-reflection IR and UV–Vis spectra. When a potential is controlled in the region of 0.7–0.8 V which is slightly higher than that of monomer oxidation, a regularly α,α′-linked polymer is obtained which has an average chain length of about 21 thiophene rings and an absorption peak of 482 nm at its neutral state. An oxidation potential higher than 0.8 V is found to lead to the occurrence of mislinkage, while an oxidation potential lower than 0.7 V only produces oligomers. The polyterthiophene prepared by control of the oxidation potential has further been cycled in BFEE to check its electrochemical stability. Comparing with the polymers from thiophene and bithiophene, the thin polyterthiophene film adhering onto a stainless-steel electrode exhibits a better cycling behaviour.