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

摘要

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 (ΔT %) 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 ΔT % 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.