Electrochemical Properties of Thin Films of Polythiophene Polymerized on Basal Plane Platinum Electrodes in Nonaqueous Media

In this paper the electrochemical properties of polythiophene thin films synthesized on single-crystal platinum electrodes are studied. It was found that the electrochemical properties, ion transport kinetics, and morphology of the polythiophene films depend on the surface orientation of the single-crystal platinum electrode used for their electropolymerization. Different oxidation levels, regarded as neutral, polaron, bipolaron, and metallic states, are usually found in conjugated heterocyclic polymers. However, the transitions between the different oxidation levels were never clearly observed in cyclic voltammetry. Instead the voltammograms usually show broad oxidation and reduction peaks with some shoulders. With the use of single-crystal platinum electrodes, it was found that polythiophene has a well-defined redox process at low potential, not observed before, possibly related to the conversion from the neutral state to polarons. On the other hand, two well-defined consecutive steps were found during the ion exchange reaction of thin films of polymer, both characterized by nucleation kinetics. This is the first report of two consecutive nucleation processes during the ion exchange process of a conducting polymer. The results presented here could further illuminate the mechanism in which the electron is transported in organic semiconductor materials.