POLYANILINES AND SUBSTITUTED POLYANILINES - A COMPARATIVE-STUDY OF THE RAMAN-SPECTRA OF LEUCOEMERALDINE, EMERALDINE AND PERNIGRANILINE

Raman spectra of the leucoemeraldine, emeraldine and pernigraniline bases have been systematically studied in resonance Raman Scattering with different excitation wavelengths and analysed in details. By using different model compounds, we have made a complete assignment of the Raman and IR vibrational modes. A dynamical calculation based on a valence force-field leads to the determination of force constants between atoms in relationship with the nature of chemical bonds. and in particular the aromatic or quinoid character for the benzene rings. The modifications between neutral and protonated emeraldine forms are well interpreted and the role of the electronic distribution around the nitrogen atom is clearly put in evidence. These studies have been extended to the sustituted compound POT (poly-o-toluidine). Based on the above calculations, an assignment is also proposed for Raman modes of the substituted polymer, leading to a clear understanding of the photo-induced IR spectra recorded on the same samples.