Copolymerization of 2,2-dithiodianiline (DTDA) and aniline (An) was performed electrochemically by cyclic voltammetry on Pt electrode in 1 M HCl. The copolymerization rate is strongly dependent on the amount of DTDA in the comonomer feed. The composition of the copolymeric films were determined by X-ray photoelectron spectroscopy (XPS) and were controlled by changing comonomer feed ratios. The fraction of DTDA units in the copolymers is proportional to the fraction of DTDA in the comonomer feeds. The reactivity of An decreases by increasing the amount of DTDA in the comonomer feed. Scanning electron microscopy (SEM) photographs show that there exist clear differences in morphology of the polymer films at various DTDA concentrations. (C) 2002 Elsevier Science B.V. All rights reserved.