The six-member ring self-doping structure in sulfonated polyaniline

By the method of FT-IR spectra, the six-member ring doping structure has been confirmed in sulfonated polyaniline for the first time. The six-member ring self-doping structure is composed of the sulfonic group and the imine group in the ortho position of the SPAn backbone. The influence of different acid, alkaline and salt on the ring doping structure has been studied by the quantitative spectra analysis technique. Because the ring structure is a stable structure in energy, it is difficult for inorganic salt, dilute acid and dilute alkaline to break it up, as the result the DC conductivity is independent of pH value in the period of 1<pH<14. While treated by concentrated sulfuric acid and strong sodium–hydroxide, the ring doping structure was destroyed. Phosphoric acid can destroy the ring structure more easily than hydrochloric acid and sulfuric acid.