Electrosynthesis and characterization of a new multielectrochromic copolymer of 1,4‐bis(2‐thienyl) benzene with 3,4‐ethylenedioxythiophene

A copolymer based on 1,4‐bis(2‐thienyl) benzene (BTB) and 3,4‐ethylenedioxythiophene was electrochemically synthesized in acetonitrile containing sodium perchlorate (NaClO 4 ). Cyclic voltammetry, ultraviolet–visible spectroscopy, and Fourier transform infrared analyses confirmed that the resulting polymer was a copolymer rather than a blend or a composite of the respective homopolymers. Poly(1,4‐bis(2‐thienyl) benzene) has only two colors; it switches between yellow in the neutral state and green in the oxidized state, whereas the poly[1,4‐bis(2‐thienyl) benzene‐ co ‐3,4‐ethylenedioxythiophene] (PBTBE) film exhibited five different colors (brown–red, orange–yellow, yellowish green, green, and blue). This revealed distinct electrochromic properties from that of the BTB homopolymer film. The maximum optical contrast (Δ T %) and response time of the copolymer film were measured to be 27.8% and 0.51 s, respectively, at 780 nm. An electrochromic device (ECD) based on PBTBE and poly(3,4‐ethylenedioxythiophene) was also constructed and characterized. This ECD showed a Δ T % value of 22.2% in the visible region with a response time of 0.43 s at 616 nm. The coloration efficiency of the device was calculated to be 129 cm 2 /C at 616 nm. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012