Electrochemical and in situ Raman spectroscopic study on the stability of poly(<Emphasis Type="Italic">N</Emphasis>-methylaniline)

The stability of poly(N-methylaniline) (PNMA) as electrode material has been studied in aqueous solutions of sulfuric acid with the use of electrochemical and in situ Raman spectroscopic techniques. It has been shown that the electrochemical decomposition of electrodeposited PNMA films follows a first-order reaction kinetics. The decomposition rate constants vary between 1.2 × 10⁻⁵ and 2.0 × 10⁻³ s⁻¹ for electrode potential varying between 0.2 and 1.0 V vs Ag/AgCl, respectively. In situ Raman spectroscopy has been applied in obtaining kinetic data at selected electrode potentials, and good correlation of these data with the corresponding data obtained by cyclic voltammetry has been found. As compared to polyaniline, the decomposition of PNMA proceeds at nearly the same rate at electrode potentials not exceeding 0.5 V. The decomposition of PNMA proceeds faster within the potential limits of 0.5 to 0.8 V and slower at electrode potentials exceeding 0.8 V as compared to polyaniline. This article is dedicated to Professor Algirdas Vaškelis (Institute of Chemistry, Vilnius, Lithuania) on the occasion of his 70th birthday and in honour of his contributions to electrochemistry and physical chemistry.