KINETIC-STUDY OF THE BITHIENYL ELECTROPOLYMERIZATION

The electropolymerization process of bithienyl (BT) in electrolyte sol utions of acetonitrile and propylencarbonate at Pt-, Ni- and Ti-electr odes has been systematically studied by means of cyclic voltammetry an d potential step chronoamperometry methods. The well-reproducible cycl ic voltammograms (CVGs) indicate that the mechanism of BT electropolym erization is independent of the solvent and electrode material. From T afel plots with a slope of 61 +/- 2 mV electrochemical parameters such as E(BT)(ox), alpha, n and i(0) of the BT oxidation were determined. The charge Q(gr) for chain growth of the polymer is proportional to BT concentration, to the number of sweeps and to the reverse potential. The degree of oxidation d(PBT)(ox) of the PBT can be determined throug h the charge Q(gr) and the charge Q(PBT)(ox) of the PBT oxidation. The ratio Q(PBT)(ox)/Q(gr) vs the number of sweeps yields a straight line giving d(PBT)(ox) < 0.45 at the stationary electrode and d(PBT)(ox) < 0.66 at the rotating disk electrode, respectively. The formation proc ess of the PBT films was observed by means of REM. The film formation undergoes nucleation, spherical nuclei growth in three dimensions and their overlapping each other to form a layer. This process is repeated layer by layer. The BT diffusion coefficient is calculated from the c urrent response to large potential steps. (C) 1997 Elsevier Science Lt d.