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, H-1 NMR, and C-13 NMR spectroscopy. Spectroelectro-chemical studies showed PETI had better electrochromic properties and showed two different colors (brown and blue-violet) under various potentials with better maximum contrast (DT%) 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. (C) 2017 Wiley Periodicals, Inc.