Conformational movements explain logarithmic relaxation in conducting polymers

Logarithmic relaxation associated with the electrochemical oxidation of con ducting polymer films after polarization to high cathodic potentials for lo ng periods of time can be explained by means of the electrochemically stimu lated conformational relaxation (ESCR) model. The key idea in the ESCR trea tment is that conducting films attain a compacted and closed structure as t hey 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 fur ther oxidation, which therefore must be preceded by the relaxation of the s tructure. A logarithmic dependence between the coefficient of cathodic pola rization (z(c)) and the wait time was obtained from chronoamperometric anal ysis. The ESCR model makes use of this result to explain the retard observe d in both anodic chronoamperograms and voltammograms as the cathodic polari zation time is shifted to higher values. (C) 1999 Elsevier Science Ltd. All rights reserved.