Conformational movements explain logarithmic relaxation in conducting polymers

Abstract

Logarithmic relaxation associated with the electrochemical oxidation of conducting polymer films after polarization to high cathodic potentials for long periods of time can be explained by means of the electrochemically stimulated conformational relaxation (ESCR) model. The key idea in the ESCR treatment is that conducting films attain a compacted and closed structure as they are submitted to cathodic polarization. Moreover, longer reduction times promote a higher compactness of the polymeric structure, making difficult the exchange of counterions between the polymer and the solution during further oxidation, which therefore must be preceded by the relaxation of the structure. A logarithmic dependence between the coefficient of cathodic polarization ( z c ) and the wait time was obtained from chronoamperometric analysis. The ESCR model makes use of this result to explain the retard observed in both anodic chronoamperograms and voltammograms as the cathodic polarization time is shifted to higher values.