In situ Raman spectroelectrochemical study of self-doped polyaniline degradation kinetics

The kinetics of electrochemical degradation for a self-doped sulfonated polyaniline derivative (a copolymer of aniline and m-aminobenzenesulfonic acid) has been studied with in situ Raman spectroscopy. It has been shown that the degradation proceeds faster in more acidic solutions. From the data obtained, first-order degradation rate constants have been calculated. Within the solution pH range of 0.5–9.0, first-order rate constants thus obtained vary, respectively, between (6.6 ± 0.8) × 10−4 s−1 and (0.8 ± 0.1) × 10−4 s−1 for electrode potential of 0.8 V vs. Ag/AgCl. A linear correlation between the degradation rate constant and solution pH has been found: log k = log k0 + a · pH, where k represents rate constant at any pH (expressed in s−1), k0 is the rate constant for pH 0, log k0 = −3.09, and a = −0.11 is the slope of (log k, pH) dependence.