Alternative explanation of asymmetry in cyclic voltammograms for redox reaction of poly(3-methylthiophene) films in acetonitrile solutions (original) (raw)

A new explanation of the asymmetry and large anodic residual current in the cyclic voltammograms for redox reactions of poly(3-methylthiophene) is proposed on the basis of voltammetric measurements for ®lms of dierent thicknesses. A specially designed measurement procedure shows that the anodic branch is a superposition of two overlapping oxidation peaks. The less positive peak is ascribed to oxidation of long-chain polymer segments which are formed mainly at the beginning of the electropolymerisation. The more positive peak originates from oxidation of short-chain segments which mainly contribute to the polymerisation of thick ®lms. Thick poly(3-MeT) ®lms, with polymerisation charges larger than 12 mC cm À 2 , are a mixture of the long-and short-chain segments due to participation of oligomers in the extended polymerisation process. The thin ®lms are better-ordered and more compact than the thicker ones. The change in morphology of the poly(3-MeT) ®lms is con®rmed by the scan rate dependence of currents of both anodic peaks and by the UV-VIS absorption spectra of the ®lms. #