REDOX CHARACTERIZATION OF COMPETITIVELY-DOPED POLYPYRROLES

In a competitive doping experiment between p-toluene sulphonate and pe rchlorate, weak anion selectivity was observed. ClO4-incorporation in to polypyrrole was favoured in both acetonitrile and aqueous methanol preparation media. This result is in contrast to our previous study wh ere acetonitrile produced the same directing-effect between ClO4 and u -TSCuPc but aqueous methanol produced the inverse selectivity, and wit h greater magnitude of effect. The redox properties of PTS/ClO4 compet itively-doped thin films show anomalous behaviours. In the conventiona l redox region (at small potential values) PTS-rich films may show cha racteristic ClO4-redox behaviours, and vice versa, depending on prepar ation protocol. While the over-oxidation region at high anodic potenti als does not parallel the conventional redox trends, thus films with C lO4- type conventional redox show PTS-type over-oxidation, and vice ve rsa, depending on preparation procedure. The results suggest a distinc tion in the origins of conventional redox and over-oxidixation. Compet itive doping provides a means of producing polypyrroles with hybrid re dox properties and other behavioural subtleties.