Poly(o-toluidine) (POT) and poly(2-chloroaniline) (P2ClAn) emeraldine salts were synthesized chemically by using formic (HCOOH), acetic (CH3COOH), propionic (C2H5COOH), and boric (H3BO3) acids. Ultraviolet-visible absorption spectra (UV-Vis) analysis results indicated that POT has the better protonation effects than P2ClAn. Among the POTS synthesized using the four different acids, POT(H3BO3) showed the least protonation effect. The conductivities of prepared polymers were measured by a four-probe technique. The highest conductivities were obtained in POTS synthesized by using formic, acetic, and propionic acids. Magnetic susceptibility measurements of the polymer salts were analyzed by using Gouy scale and it was found that POT(CH3COOH) and POT(C2H5COOH) salts are of bipolaron structure; other polymer salts are of polaron structure. The characterization of the polymers were investigated by Fourier infrared spectroscopy (FTIR), UV-Vis, thermogravimetric analysis, and scanning electron microscopy. It was observed from UV-Vis spectra of the emeraldine salt of POT that wavelengths belonging to pi-->pi* transitions shifted to shorter wavelengths with increasing pKa values of acids. POT and P2ClAn synthesized in faun different protonation media decomposed with three-step and three- or two-step weight loss, respectively. (C) 2002 Whey Periodicals, Inc.