Influence of anions on formation and electroacitivity of poly-2,5-dimethoxyaniline

The electrodeposition and electroactivity of poly-(2,5-dimethoxyaniline) (PDMA) were studied in several strong acid solutions: HCl, H2SO4, HClO4, and CCl3COOH by cyclic voltammetry and in situ UV/VIS and EPR measurements. The monomer oxidation potential is shifted towards negative values in comparison to aniline and (2-methoxyaniline). The shift is influenced by the kind of acid, i.e., the monomer oxidation potential is about 0.18 V lower in the HClO4 than in the H2SO4 solution. Presence of two electron donor substituents induces also interesting properties of the resulting polymer. The shapes of PDMA cyclic voltammograms (redox peaks' positions and currents) strongly depend on the kind of anion, while in the case of polyaniline and poly(2-methoxyaniline) the kind of anion does not affect redox peak positions so significantly. The very unusual feature of PDMA is significant concentration of polarons at potentials, where the reduced polymer is expected, indicated by the in situ EPR and UV/VIS measurements. The EPR signal is split, what. suggests presence of two kinds of polaron species. This observation is supported also by the UV/VIS results. Similarly to polyaniline, the kind of anion influences the PDMA degradation, however this process starts at much lower potentials in comparison to polyaniline. (C) 2000 Elsevier Science S.A. All rights reserved.