Green and efficient electrosynthesis of poly-3,4-ethylenedioxythiophene in aqueous micellar solution of zwitterionic surfactant

Abstract

In this work, a biocompatible and biodegradable zwitterionic surfactant SB3-14 (n-tetradecyl-N, N-dimethyl-3-ammonio-1-propanesulfonate) was chosen to replace nonionic surfactant polyoxyethylene-10-laurylether (C12E10) to solubilize the poorly water-soluble monomer 3,4-ethylenedioxythiophene (EDOT), and in the micellar solution of SB3-14, the anodic polymerization of EDOT was studied to demonstrate the advantage of the zwitterionic surfactant over the nonionic surfactant. Compared with C12E10, SB3-14 is neither adsorbed on the glassy carbon electrode (GCE) over −0.2～1.0 V vs SCE, nor oxidized at the high oxidative polymerization potential for EDOT. These unique properties are favorable not only for the enhancement of the electropolymerization rate, but also for the improvement of the current efficiency. A comparative study on the electropolymerization modes, i.e., the constant potential mode and the pulsed potential mode, indicates that at high oxidative polymerization potential, the EDOT electropolymerization reaction is limited by the diffusion mass transfer of the electroactive monomer, and the growth rate of the polymer PEDOT can be significantly increased by prolonging the duration time of the pulse lower limit potential. At low oxidative polymerization potential, however, the EDOT polymerization reaction is basically controlled by the heterogeneous charge transfer process, and the electropolymerization modes have little effect on the growth rate of the PEDOT film. The XPS data of the PEDOT films demonstrate that SB3-14 is not doped (encapsulated) into the PEDOT film, and ClO4− is the only doping species. The doping level of the PEDOT film is determined by the oxidative polymerization potential and the electropolymerization mode. At high oxidative polymerization potential, the pulsed potential mode results in a PEDOT film with higher doping level than the constant potential mode does due to the periodic relaxation of the monomer concentration gradient as well as the full doping of the polymer in the duration time of the pulse lower limit potential. The above studies demonstrate that this new strategy is helpful for the green and efficient electrosynthesis of high quality PEDOT.