Conformational movements explain logarithmic relaxation in conducting polymers

摘要

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 conformationalrelaxation (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 polymericstructure, 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 cathodicpolarization (z{sub}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 shiftedto higher values.