ANALYSES OF SPECTROELECTROCHEMICAL BEHAVIOR OF POLYPYRROLE FILMS USING THE NERNST EQUATION - MONOMER UNIT MODEL AND POLARON/BIPOLARON MODEL

A series of the absorption spectrum changes in polypyrrole films were analyzed using the Nernst equation by two models. One is the "monomer unit model" and the other is the "polaron/bipolaron model." In the first model, formal electrode potentials and the n-values were obtained and used to fit calculated DELTA-Abs vs. E curves to the experimental plots at three wavelengths. In the second model, the "apparent" excess chemical potentials were introduced to correct for the large deviations between the Nernst equation and the Nernst plots obtained from the absorption spectra. The calculated DELTA-Abs vs. E curves were then fitted to the experimental plots. The "apparent" excess chemical potentials were assigned as corrections for species concentrations. Advantages of the monomer unit model over the polaron/bipolaron model are pointed out in the precise analyses of the spectroelectrochemical behavior of the films.