Kinetic study of the electrochemical degradation of polyaniline

The kinetics of the electrochemical degradation of polyaniline (PANI) layers, deposited by electropolymerization and chemical polymerization onto platinum electrode, was investigated in an acid aqueous solution. The degradation rate was shown to depend greatly on the electrode potential applied. First-order rate constants of degradation, obtained from the kinetic data, were shown to vary between 2.87 x 10(-5) and 3.11 X 10(-3) s(-1) for thick PANI films, having the electrochemical charge density of 14 mC/cm(2) and between 2.0 x 10(-5) and 3.60 x 10(-3) S-1 for thin PANI films, having the charge density of 1.5 mC/cm(2), within the electrode potential range of 0.3-0.9 V versus Ag/AgCl. Two linear regions were found to present on the dependencies of logarithm of the first-order degradation rate constant on electrode potential, one of them having a slope of 0.44 and 1.34 V-1 within electrode potential limits of 0.3-0.6 V, and another one having a slope of 6.37 and 6.39 V-1 within potential limits of 0.6-0.9 V, for thick and thin polymer films, respectively. The results obtained show that the electrochemical degradation of PANI films proceed at a remarkable rate even at low electrode potential values. (C) 2001 Elsevier Science B.V. All rights reserved.