Electropolymerization of polypyrrole at the three-phase interline: Influence of polymerization conditions

Abstract

Free-standing polypyrrole film was electrosynthesized at the interface between an HClO4 aqueous solution and a pyrrole chloroform solution through a dynamic three-phase interline electropolymerization (D3PIE) process. The cyclic voltammetary measurements showed that the onset potential for the oxidation of pyrrole monomers was ∼0.2V vs. Hg/Hg2SO4, and the radial expansion of conductive polymer film gradually increased the reaction currents. Under potentiostatic conditions, higher potentials, higher counterion (perchlorate) concentrations and higher monomer concentrations all caused a faster growth of polymer, and the aqueous perchlorate ions appeared the most sensitive factor for the reaction currents. In the initial stage of electropolymerization, the reaction currents and the diameters of polymer films increased linearly with the operating times, and a simple model can be used to describe the growth behavior of the circular polymer film. However, several factors can cause the deviation from an ideal linear relation in the later stage of electropolymerization. Higher aqueous perchlorate concentration increased the penetration amount of perchlorate ions to organic solvent phase, resulting in the longitudinal growth of PPy polymers. In addition, the prepared PPy films exhibited significantly different microstructures between the side toward water and the side toward organic solvent, and the aqueous perchlorate concentration and monomer concentration both affect the morphologies of films greatly. In order to observe a well-defined expansion of three-phase interline, lower concentrations of aqueous perchlorate ions and monomers are preferable.