Quantitative characterization of polyaniline films using Raman spectroscopy I: Polaron lattice and bipolaron

Polyaniline is generally depicted using five schematic structures: leucoemeraldine, emeraldine and pernigraniline bases, and then emeraldine salt in polaron lattice or bipolaron forms. Films obtained by electropolymerization in acidic solution present all the intermediate organizations between these structures. The paper aims to point out the potentiality of the Raman spectroscopy (RS), only technique able to describe the actual polyaniline because it gives a molecular nomenclature of the polymer. This potentiality is generally undervalued, in reason of the spectra complexity. Here, a very simple Raman spectra treatment is used to obtain a quantitative characterization of polyaniline films. One can follow the progressive passage between the different polarons organizations displayed in function of the polarization potential: polaron lattice, then bipolaronic species are successively formed in the conductive range, and the passage from one to another form corresponds to the maximum of conductivity. RS is associated here to optical spectroscopy. (c) 2006 Elsevier Ltd. All rights reserved.