A novel conducting polymer based on terthienyl system bearing strong electron-withdrawing substituents and its electrochromic device application

A novel conducting polymer bearing strong electron-withdrawing substituents (EWS) directly attached to the 3,4-positions of the thiophene ring was synthesized by electrochemical polymerization of diethyl 2,5-di(thiophen-2-yl)thiophene-3,4-dicarboxylate (SSS-Diester). The polymer (PSSS-Diester) was characterized by cyclic voltammetry, FT-IR and UV–vis spectroscopy. The polymer has a reversible redox process and demonstrates a stable electrochromic behavior; reddish orange in the neutral state, brown in the intermediate state and green in the oxidized state. Optical density and response time of the dual-type electrochromic device based on PSSS-Diester were found to be 0.23 and 0.6 s at 623 nm, respectively. It is also noteworthy that the device shows good environmental and redox stability (i.e. 94% of the optical activity of the device retained after 500th switch).