Poly (o-toluidine) (POT) salts doped with organic sulfonic acids (beta-naphthalene sulfonic acid, camphor sulfonic acid, and p-toluene sulfonic acid) were directly synthesized by using a new solid-state polymerization method. The FTIR spectra, ultraviolet visibility (UV-vis) absorption spectra, and X-ray diffraction patterns were used to characterize the molecular structures of the POT salts. Voltammetric study was done to investigate the electrochemical behaviors of all these POT salts. The FTIR and UV-vis absorption spectra revealed that the POT salts were composed of mixed oxidation state phases. All POT salts contained the conducting emeraldine salt (half-oxidized and protonated form) phase; the pernigraniline (fully oxidized form) phase is predominant in POT doped with beta-naphthalene sulfonic acid, and POT doped with p-toluene sulfonic acid had the highest doping level. The X-ray diffraction patterns showed that the obtained POT doped with organic sulfonic acids were lower at crystallinity. The conductivity of the POT salts were found to be of the order 10(-3)-10(-4) S/cm. (c) 2005 Wiley Periodicals, Inc.