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

Raman spectra of the leucoemeraldine, emeraldine and pernigraniline ba ses have been systematically studied in resonance Raman Scattering wit h different excitation wavelengths and analysed in details. By using d ifferent model compounds, we have made a complete assignment of the Ra man and IR vibrational modes. A dynamical calculation based on a valen ce force-field leads to the determination of force constants between a toms in relationship with the nature of chemical bonds. and in particu lar the aromatic or quinoid character for the benzene rings. The modif ications between neutral and protonated emeraldine forms are well inte rpreted and the role of the electronic distribution around the nitroge n atom is clearly put in evidence. These studies have been extended to the sustituted compound POT (poly-o-toluidine). Based on the above ca lculations, an assignment is also proposed for Raman modes of the subs tituted polymer, leading to a clear understanding of the photo-induced IR spectra recorded on the same samples.