Conformational relaxation during polypyrrole oxidation: From experiment to theory

The closure of the polymeric entanglement is proposed to occur during the expulsion of small anions from an oxidized polypyrrole film during reduction. The compactness of the polymeric structure rises by polarization at more cathodic potentials. So increasing anodic overpotentials are required to promote conformational relaxation, allowing the penetration of counterions into the polymer matrix, as was observed experimentally from thick (15 mu m) polypyrrole films in 0.1 M LiClO4/acetonitrile solutions. The relaxation controlled oxidation is not uniform: it is initiated on different points on the polymer electrolyte interface, as was confirmed by chronoamperometry. The developed electrochemical relaxation model, including this like-nucleation behaviour of the relaxation process, is able to simulate experimental chronoamperograms. A good agreement between theoretical and experimental results was obtained.