A new copolymer of N-(4-(3-thienyl methylene)-oxycarbonylphenyl)maleimide (MBThi) with thiophene [P(MBThi-co-Th)] was synthesized electrochemically in the presence of tetrabutylammonium tetrafluoroborate as the supporting electrolyte, in acetonitrile/borontrifluoride ethylether solvent mixture (80 : 20, v/v). Spectroelectrochemical analysis of the resulting copolymer reflected electronic transitions at 440, 730, and similar to 1000 nm, revealing pi-pi* transition, polaron, and bipolaron band formation, respectively. Switching ability was evaluated by a kinetic study via measuring the transmittance (%T) at the maximum contrast. Dual-type polymer electrochromic devices (ECDs) based on P(MBThi-co-Th) and poly(ethylene dioxythiophene) (PEDOT) were constructed. Spectroelectrochemistry, switching ability, and stability of the devices were investigated by UV-vis spectroscopy and cyclic voltammetry. These devices exhibit low switching voltages (between 0.0 and +2.0 V) and short switching times with reasonable switching stability under atmospheric conditions. (c) 2006 Wiley Periodicals, Inc.