Role of conformational relaxation on the voltammetric behavior of polypyrrole. Experiments and mathematical model

Anomalous effects associated with the electrochemical cycling of electrogenerated polypyrrole films after polarization at high cathodic potentials were simulated from a derivation of the electrochemically stimulated conformational relaxation model. The cathodic treatment promotes the compaction of the polymer by conformational movements of polymeric segments. The compacted structure requires, at constant temperature, an anodic overpotential (that is, an extra energy) to be opened during oxidation, allowing the penetration of counterions from the solution in order to keep the electroneutrality in the film. The definition of a conformational relaxation time for the swelling of the polymeric structure, including both thermal and electrochemical energetic contributions, allows the integration of structural parameters on electrochemical equations. Theoretical voltammograms reproduce the effect of the different variables (cathodic potential, sweep rate, and temperature) and fit experimental results for polypyrrole films.