UV-VIS-NIR AND RAMAN SPECTROELECTROCHEMISTRY OF REGIOREGULAR POLY(3-OCTYLTHIOPHENE) - COMPARISON WITH ITS NON-REGIOREGULAR ANALOG

Spectroelectrochemical behaviour of regioregular poly(3-octylthiophene ) has been investigated using UV-VIS-NIR and Raman spectroscopies. Sta tic and dynamic UV-VIS-NIR spectroelectrochemical experiments combined with cyclic voltammetry show that oxidative doping of the regioregula r polymer is a two-step process in which polarons (radical cations) ar e first created which then recombine to bipolarons (dications). This t wo-step oxidative doping mechanism is corroborated by FT Raman spectro electrochemical studies which show significant changes in the position s and intensities of the Raman bands coinciding with the first and sec ond oxidation peaks in cyclic voltammetry. These changes can be interp reted in terms of the doping induced formation of quinoid sequence of bands in the oxidized polymer. Vibrational calculations carried out fo r undoped and doped poly(3-octylthiophene) gave a very good agreement between the calculated Raman band frequencies and those recorded exper imentally for the regioregular polymer.