Electropolymerization and characterization of COOH-functionalized poly(3,4-ethylenedioxythiophene): Ionic exchanges

► COOH-functionalized EDOT was successfully electropolymerized by different methods. ► Stored specific charges are higher than those stored in PEDOT. ► Both anion and cation ionic exchange are observed by EQCM experiments. ► UV-Vis spectroelectrochemical results are similar to those obtained from PEDOT. ► After deep p-dedoping some kind of hysteresis is observed during p-doping.