Two series of terpolymers, one of o-/m-toluidine and aniline with o-amino-benzoic acid and the other of o-/m-toluidine and aniline with m-aminobenzenesulfonic acid, have been synthesized by oxidative polymerization via an emulsion method with ammonium persulfate as the oxidant and HCl as the external dopant. The terpolymers exhibit excellent solubility and retain the high conductivity (similar to 1 S cm(-1)) characteristic of the unsubstituted homopolymer, polyaniline. The terpolymers also possess higher thermal stability than polyaniline. This can be attributed to the presence of internal doping groups and substituents, which introduce flexibility to the otherwise rigid polyaniline backbone. (c) 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3040-3048, 2005.