Doping effect of organic sulphonic acids on the solid-state synthesized polyaniline

Polyaniline (PANI) salts doped with organic sulfonic acids (methanesulfonicacid, p-toluenesulphonic acid, and dodecylbenzenesulphonic acid) were first synthesized by using solid-state polymerization method. The polymers were characterized by Fourier transform infrared (FTIR) spectra, ultraviolet-visible spectrometry, X-ray diffraction, cyclic voltammetry, scanning electron microscopy, transmission electron microscopy, and conductivity measurements. It was found that PANI doped with p-toluenesulphonic acid is formed in conductive emeraldine oxidation state, and displayed higher doping level and cyrstallinity. On the contrary, PANI doped with dodecylbenzenesulphonic acid was lower at doping level and highly amorphous. In accordance with these results, the conductivity and electrochemical acitivity was also found to be higher in p-toluenesulphonic acid-doped PANT, and these properties were opposite in the case of dodecylbenzenesulphonic acid. The results also revealed that the morphology of dodecylbenzenesulphonic acid-doped PANI was remarkably different from other PANI salts. (c) 2007 Wiley Periodicals, Inc.