A novel copolymer based on aniline and N-beta-cyanoethylaniline was chemically prepared and characterized by a number of techniques including UV-vis, FTIR, ESR, XRD, and TGA. According to the systematic studies on the physical properties, it was found that the copolymers had excellent solubility in common organic solvents especially in DMF and pyridine, while the conductivity and yield decreased as the content of cyanoethyl group increased in the system. Moreover, an increase in the feed ratio of N-beta-cyanoethylaniline induced a blue-shift of the absorption bands in the UV-vis and IR region and significant line broadening of ESR signals together with a reduction in spin density. The XRD patterns of the copolymers lost the characteristic diffraction peaks of emeraldine salt as the ratio of cyanoethyl group increased. The thermal stability of the copolymer was increased with increasing the feed molar ratio of N-beta-cyanoethylaniline. (C) 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 140-147, 2007