8894
Langmuir 2003, 19, 8894-8898
Adsorption-Assisted Electro-oxidation of Dioxypyrrole and Dioxythiophene Monomers Probed by Fast Cyclic Voltammetry Fabien Miomandre,† Pierre Audebert,*,† Kyukwan Zong,‡ and John R. Reynolds*,‡ Laboratoire PPSM, CNRS UMR 8531, Ecole Normale Supe´ rieure de Cachan, 94235 Cachan, France, and Department of Chemistry and Center for Macromolecular Science and Engineering, University of Florida, Gainesville, Florida 32611-7200 Received February 26, 2003. In Final Form: July 14, 2003 The reactivity of the cation radicals formed by oxidation of four 3,4-alkylenedioxypyrrole and 3,4alkylenedioxythiophene monomers has been investigated by fast scan cyclic voltammetry, from the V/s to the kV/s range. The results show that all cation radicals react quickly as desired for electropolymerization and electroactive polymer film formation on platinum and glassy carbon electrodes, despite the strong donating effect of the O-alkyl substituents. Surprisingly, the chemical reversibility of the cation radical formation and subsequent neutralization is easily observed on gold, due to a strong adsorption phenomenon, which greatly enhances the lifetime of the electrogenerated cation radical and reduces its formation potential. Surface coverage and electronic transfer coefficient measurements comparing the dioxypyrrole and dioxythiophene derivatives suggest a difference in how the adsorbed molecules orient relative to the electrode surface.
Introduction Electro-oxidative polymerization of heterocycles with concurrent polymer film deposition has proven to be an especially useful method for the preparation of electroactive and conducting polymer films.1 Polymers prepared in this manner exhibit useful conductivity, electrochromic, electrocatalytic, electromechanical actuation, and drug release properties.2 The electropolymerization process is facilitated by the fact that in many heterocycle systems, the anodically formed cation radicals rapidly couple to form dimeric and higher oligomeric species. In fact, potential scanning electrochemical studies (cyclic voltammetry, CV) at standard sweep rates (
