This study covers the synthesis of polymers of aniline, in-chloroaniline and their copolymers by chemical oxidation in HCl medium. The composition of the copolymers was varied by varying the comonomer feed ratio in the polymerization reactions. For examining the effect of composition on copolymer solubility, viscosity, density, spectral characterization and electrical properties were studied. The electrical conductivity of the compressed pellets were measured by two probe method. The copolymer exhibits excellent solubility in DMF, DMSO and THF. The spectroscopic analysis, solubility test, viscosity, density and electrical conductivity suggest that aniline and m-chloroaniline units are distributed along the copolymer chain and the properties of copolymers can be modified by varying the monomer composition in copolymerization reactions. It was found that the room temperature conductivity of the copolymer decreases with increase of the in-chloroaniline content in copolymerization reaction, because of the introduction of the Cl--(-) group reducing the conjugation of the polymer chain. (c) 2005 Elsevier B.V. All rights reserved.