2-((2,3-Dihydrothieno[3,4-b]dioxin-2-yl)methoxy)methyl oxirane (EDOT-MO) was successfully synthesized by the reaction of epichlorohydrin with hydroxymethylated-3,4-ethylenedioxylthiophene (EDOT-MeOH), which was synthesized via a simple four-step sequence. Poly(hydroxymethylated-3,4-ethylenedioxylthiophene) (PEDOT-MeOH) and poly(2-((2,3-dihydrothieno[3,4-b]dioxin-2-yl)methoxy)methyl oxirane) (PEDOT-MO) were electrosynthesized through electropolymerization of EDOT-MeOH and EDOT-MO, respectively. Structural, electrochemical, optical, and thermal properties of as-formed polymers were investigated by FTIR, cyclic voltammetry, UV-vis, and thermogravimetry. Spectroelectrochemistry studies demonstrated that PEDOT-MeOH and PEDOT-MO could be reversibly oxidized and reduced accompany with obvious color changes. Further kinetic studies demonstrated that the introduction of hydroxymethyl or ethylene oxide group significantly improved electrochromic properties of 3,4-ethylenedioxythiophene (PEDOT) and resulted in high contrast ratios (57.3% at 585 nm) and coloration efficiencies (338.5 cm2 C-1), low switching voltages, and fast response time. (c) 2014 Wiley Periodicals, Inc.