In situ resonance Raman spectroelectrochemistry of polypyrrole doped with dodecylbenzenesulfonate

In situ Raman spectroelectrochemistry was performed on cycled polypyrrole films incorporating dodecylbenzenesulfonate (DBS). It was found that under 457.9 nm excitation, the neutral form was resonant and the bands due to the neutral form of the polymer dominated the spectra. Spectra obtained using 514.5 nm excitation displayed a strong neutral contribution but bands due to the radical cation and dication were also visible. At 632.8 nm excitation, the bands assigned to the radical dication were dominant, with a noticeable contribution from the dication in the oxidised state. The strength of the radical cation contribution is unusual as it made only a weak contribution in the UV–vis adsorption spectra. The CC backbone stretching band between 1560 and 1590 cm−1 was found to be made up of a contribution of bands due to the radical cation and neutral forms with a separate band at 1620 cm−1 for the dication form. The results show that by carefully selecting the excitation wavelength, resonance Raman is a powerful tool for analysing the changes in oxidation states of a conducting polymer under potential cycling.