Characterization of poly(N-alkylanilines) by Raman spectroscopy

Thin films of poly(N-alkylaniline) were synthesized in acidic aqueous solution and in mixtures of aqueous and organic solvents. The polymer films (alkyl = methyl, ethyl, propyl and butyl) were characterized by Raman spectroscopy with the excitation wavelengths of 514.5, 632.8 and 780 nm. The main Raman bands have been characterized for the leucoemeraldine, emeraldine and pernigraniline oxidation states between −0.2 and 0.8 V (vs. Ag|AgCl). This fundamental study shows that the structure of the half-oxidized emeraldine form contains quinoid units, which supports the commonly accepted oxidation and reduction scheme of poly(N-alkylanilines).