Partially sulfonated polyaniline: conductivity and spectroscopic study

Polyaniline and set of copolymers of aniline with orthanilic acid (OA) were prepared by oxidation of monomers with ammonium peroxydisulfate. Amount of OA in mixture of comonomers was varied from 0 to 10%. The higher amount of OA resulted in decrease of conductivity and increased steepness of temperature dependence of conductivity. The X-ray photoelectron spectroscopy showed content of self-doping groups in surface layer slightly higher than expected from the feed ratio of comonomers. Shifts of positions of bands of ring stretching vibrations towards their position in polyaniline base and shift of the band of protonated units Q=NH⁺–B or B–NH^+?–B in the FTIR spectra observed with increasing amount of OA have shown increase of electron localization in copolymers. Finally, Raman spectroscopy proved that sulfonic groups act as structural defects in polymer’s geometry. Polarons are expected to be localized on short isolated segments between the structural defects.