A Free-Standing Electrochromic Material of Poly(5,7-bis(2-(3,4-ethylenedioxy)thienyl)-indole) and Its Application in Electrochromic Device

Free-standing poly(5,7-bis(2-(3,4-ethylenedioxy)thienyl)-indole) (PETI) was electrochemically obtained from 5,7-bis(2-(3,4-ethylenedioxy)thienyl)-indole (ETI) prepared by Stille coupling reaction of 5,7-dibromoindole and 3,4-ethylenedioxythiophene. For comparison, poly(5,7-bis(2-thiophene)-indole) was also electrosynthesized from 5,7-bis(2-thiophene)-indole (BTI) which was prepared from the 5,7-dibromoindole and thiophene. Characterizations of ETI and BTI were performed by cyclic voltammetry, scanning electron microscopy, 1H NMR, and 13C NMR spectroscopy. Spectroelectrochemical studies showed PETI had better electrochromic properties and showed two different colors (brown and blue-violet) under various potentials with better maximum contrast (ΔT%) and coloration efficiency (CE). An electrochromic device (ECD) based on PETI and poly(3,4-ethylenedioxythiophene) (PEDOT) was also constructed and characterized. This ECD had fast response time, high CE, better optical memory, and long-term stability. These results indicated that PETI had potential applications for ECD. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 2356–2364