Homopolymers of aniline, toluidines and their copolymers were synthesized by chemical oxidative polymerization using different ratios of monomers in the feed in H2SO4 medium. The synthesized polymers were characterized by employing Fourier transform infrared, UV-visible, proton nuclear magnetic resonance, X-ray diffraction techniques for understanding the details of the structure of the synthesized polymers. Morphological, thermal, and electrical conductivity of the as synthesized polymers were also studied by employing scanning electron microscopy, thermogravirnetric analysis, and dc electrical conductivity, respectively. From the SEM images rod shaped nanoparticles were observed in PANI and spherical shaped nanoparticles were observed for copolymers. A three-step thermal degradation was observed for all the polymers. The electrical conductivities of the copolymers were less compared with PANE and at higher temperature the conductivities of all the polymers were more or less same. It was observed that yield and intrinsic viscosity of copolymers are not regularly dependant on monomer concentration in the feed. The copolymers show better solubility but lower conductivity than PANI. Properties of homopolymers and copolymers are also pointed out. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117: 1350-1360, 2010