RAMAN-SPECTROSCOPY OF NEUTRAL AND DOPED POLY(3-METHYL THIENYLENE) AND POLY(3-METHYL THIENYLENE)-HETEROPOLYANION COMPLEXES

In the first part of this paper is reported a Raman study performed on several electrochemically prepared poly(3-methyl thienylene) (P3MeT) films. The sample dependence of the Raman spectra is analysed. A correlation between the intensity, the frequency and the width of the Raman lines and the nature of the films under consideration (defined in terms of thickness, conjugation length, amount of structural defects and level of doping) is shown. Some Raman criteria are defined and used in order to characterize P3MeT samples from Raman spectroscopy. These Raman results are used to characterize a class of materials that are attracting much interest in electrochemistry, electrocatalytic and analytical chemistry: the poly(3-methyl thienylene)-heteropolyanion (P3Met-PHA) complexes, with PHA (SiW12O40)4- or PHA =(PMo12O40)3-. Two results can be emphasized: (i) the strong increase of the structural disorder of the P3MeT chain related to the intercalation of the PHA; (ii) the low value of the doping level or, in other words,. the poor charge transfer between the PHA and the P3MeT chain. These results question the high value of the conductivity measured in this class of compound (sigma-around 10 S cm-1) and suggest that the role of the heteropolyanions in the conductivity process cannot be ignored.