RESONANCE RAMAN-STUDY OF POLYTHIOPHENE FILMS IN THE DOPED AND UNDOPED STATES - RELATIONS BETWEEN SPECTRAL DATA AND PHYSICOCHEMICAL PROPERTIES

Polythiophene films prepared by electrochemical polymerization of thiophene were analysed, in situ and ex situ, by resonance Raman spectroscopy using several excitation wavelengths ranging between 457.8 and 1064 nm. The domain of the polymer reversibility, during oxido-reduction cycles, was strictly defined by in situ experiments and the doping yield was correlated with the intensity ratio of two bands at 1411 and 1428 cm-1 resulting from excitation at 1064 nm. Atomic force microscopy measurements have shown that disorder at the polymer surface is increasing with the film thickness. It was suggested that the doped parts of the polymer responsible of the cauliflower structure become so important that they hide the undoped parts and, thus, could explain the spectral modifications observed with increasing thickness.