Effect of sulphuric acid on the properties of polyaniline–HCl salt and its base

The effect of H2SO4 on polyaniline–HCl salt and its base was studied for different concentrations of the acid (0.1, 1.0, 4.0, 8.0, 13.0 and 18.0 M) for a duration of one day and five days. The H2SO4 treated polyaniline samples were characterised by conductivity and UV–vis, FT-IR and EPR spectroscopic measurements. Due to the incorporation of H2SO4 in the polymer chain significant effects on polyaniline–HCl salt were observed, while for the polyaniline base doping occurs depending on the concentration of H2SO4. The extent of doping and the incorporation of the sulphate group in the polymer chain are revealed by the spectroscopic and conductivity studies. The conversion of polyaniline base to the salt form is less efficient by H2SO4 doping when compared to doping by HCl.