In situ FTIR-ATR spectroscopic investigations on the redox behavior of poly(thienylpyrrole) thin film electrodes in non-aqueous solutions

Using in situ FTIR attenuated total reflection (ATR) spectroscopy, the electrochemical redox processes of poly(thienylpyrrole) (FTP) in acetonitrile (AN) solutions containing Bu4NClO4 or Bu4NPF6 were investigated. The spectra of PTP based on electrochemically induced structural changes are presented. At higher oxidation levels, a delocalization of the positive charge along the polymer chain is induced to a significant content and the intensities of IR active vibrational (IRAV) bands are dramatically increased. The relations of the intensities of IRAV bands to the oxidation potential show that at lower anodic potentials the initial charge-carrier species are polarons, while at higher potentials (>300 mV), bipolarons are also formed coexisting with the polarons. At potentials >500 mV only bipolarons exist. By comparing the intensity ratios of some characteristic bands, different conductivities of the films were observed in situ.