Anion movement and carrier type in polypyrrole/dodecyl sulfate

In situ FTIR results are presented for the electrochemical cycling of polypyrrole films containing entrapped sodium dodecyl sulfate, in aqueous sodium perchlorate and aqueous sodium carbonate solutions. In perchlorate solution, the film is oxidised in two stages, involving the formation of polarons and bipolarons; no evidence for the incorporation of the perchlorate anion within the film was found, though there was evidence for strong interactions between the charged chains and the DDS– anion. The results in carbonate solution are markedly different, with the film being oxidised in at least three stages. The first stage, at potentials up to –0.2 V, involves the generation of bipolarons, the initial ejection of protons, and the slow incorporation of carbonate into the film. The second and third stages, covering the potential ranges –0.2 to +0.1 V, and 0.1 to 0.3 V, involve the extensive uptake and coordination of carbonate into the film, with the nature of the coordination changing between the second and third stages. The films were found to be anisotropic.