Study of polaron and bipolaron states in polypyrrole by in situ Raman spectroelectrochemistry

The transitions from the reduced-polaron–bipolaron states of polypyrrole (ppy) were analyzed by in situ Raman spectroelectrochemistry. The distinct vibrational modes presented by the polymer in different oxidation levels were assigned to specific signatures of polaron and bipolaron states. As the polymer was oxidized from the neutral state, an intermediary phase featuring vibrational bands from both the benzoid (reduced) and the quinoid (oxidized) forms were observed. This intermediary phase was correlated to the polaron state. The results were compared with previous ESR data that confirm the presence of polaron and bipolaron states in the potential region where the vibrational modes of these phases were identified.