Nucleation Models for Oxidation of Conducting Polymers

The unusual cyclic voltammograms and responses to large-amplitude potential steps of a variety of conducting polymer films have prompted a number of groups to develop nucleation models for their oxidation. The key features that they have sought to explain are the peaks observed in anodic chronoamperometry (see Fig. 14), and the dependence of the anodic peak position on scan rate207 and the time spent in the undoped state.20  

Otero and co-workers208,212 have visually observed nuclei of oxidized polymer in thin polypyrrole films on electrodes. They attribute these to sites of counter-ion and solvent ingress. A nucleation model based on the growth of ionically conductive zones provides good agreement with experimental chronoamperometric responses. 

Nucleation models have also been invoked for the oxidation of polyaniline films.209,213 In both cases, the nucleation of electronically conductive zones was assumed, following Aoki s well-documented model. The possibility that the nucleation of ionically conductive regions could be rate limiting does not appear to have been considered. 

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