In order to improve the processibility of Polyaniline(PANI), PANI dispersion was prepared by oxidative dispersion polymerization of aniline with poly(methyl vinyl ether-alt-maleic acid)(PMVEMA) in aqueous medium. Ammonium persulfate(APS) was used as an oxidant and PMVEMA as a steric stabilizer and auxiliary dopant. Yield, size and dispersion stability of PANI-PMVEMA dispersion and the fraction of PMVEMA adsorbed on particle were determined for different compositions of components. PANI-PMVEMA showed the increases in yield and in particle size as the ratio of APS to aniline increased up to 1. But over the ratio of 1, the yield and particle size kept constant values. As the molar ratio of PMVEMA to aniline increased, the particle size decreased. Above the ratio of 3, the particles had the uniform size and spherical shapes. PANI-PMVEMA particles had surprisingly high electrical conductivities($lapprox$1S/cm) despite the presence of the insulation outer layer of PMVEMA. PANI-PMVEMA dispersion showed smaller pH dependence than PANI-HCl. In addition, dispersion stability was studied for different pH values by Zeta Potential and UV. PANI-PMVEMA dispersion was stable in the whole range of pH except for around pH 3 which was an isoelectric point. To investigate of thermal characteristics of PANI-PMVEMA dispersion, its conductivity stability was examined at different elevated temperatures under air and the dedoping process of PANI-PMVEMA was studied by FT-IR. PANI-PMVEMA showed the decrease in conductivity with the increasing temperature, this decreasing conductivity might be due to the decrease in doping level and in effective conjugation length.
