Fabrication of One-Dimensional Polymer Nanowires by Templated Bipolar Electropolymerization Promoted by Electrophoretic Effect

Abstract

Electropolymerization with a nanoporous template is a straightforward method to address one-dimensional (1D) polymer nanowires, while the limited monomer diffusion into the nanopores tends to give tubular structure, resulting in lower mechanical strength. In this study, bipolar electrochemistry is employed for the construction of densely packed polymer nanowires. Bipolar electrochemistry is an electrochemical system with a low concentration of an electrolyte. Thus, the electrophoretic process concomitantly proceeds, which can force the ionic monomers to migrate into the nanopores. Cationic ruthenium-polypyridine or anionic 3-thiophenetrifluoraborate were successfully polymerized by cathodic reduction or anodic oxidation, respectively, in the bipolar electrochemical system using anodic aluminum oxide templates. The obtained polymer nanowires were robust enough to keep 1D perpendicular structures, even after the removal of the templates. Systematic control experiments demonstrated the essential role of electrophoresis to address such robust nanowires. The present work sheds some light on the synergetic effect of two inherently highly compatible but overlooked distinct phenomena, bipolar electrolysis and electrophoresis.