The polymer exhibits conducting properties at potentials moro negative that the formal potential (defined as [E(p)c + E(p)a]/2) of the film. This conclusion is supported by the limiting voltammetric behaviour observed during growth of the polymer and by the results of experiments with redox couples. ESR experiments indicated that formation of polarons is maximised in the region of potential where the polymer is conducting. The polaron concentration decays at positive potentials, possibly due to formation of bipolarons. However, at these potentials polarons appear not to contribute to the conductivity of the film, which could be due to entrapment of radical cations into non-conducting regions of the polymer.