Template-free perpendicular growth of a poly(3,4-ethylenedioxythiophene) fiber array by bipolar electrolysis under an iterative potential application†
Conducting polymer fiber arrays are of great interest in material science due to their applications in organic electronic devices. Most of the reported procedures to prepare conducting polymer arrays rely on electropolymerization using a tubular template, although the use of a template gives some limitations to the design of devices as well as adding more processes for preparing and removing the template. Here, we report the template-free electrochemical fabrication of a conducting polymer fiber array by bipolar electrochemistry. Bipolar electrolysis under iterative potential application using a cylindrical insulator enabled the perpendicular growth of a uniform conducting polymer array made of poly(3,4-ethylenedioxythiophene) (PEDOT) from a wide variety of electrode surfaces. A thorough investigation of the electrolytic parameters revealed that the applied voltage and the distance between the cylinder and the bipolar electrode are pivotal for the growth of a PEDOT array, which was also implied by the results of computational simulation. Mechanistic study on the formation of the fiber array suggested that this process required an induction period to form polymers in a particular morphology, which then initiates the fiber growth. Other parameters such as the solvent, supporting electrolyte and the diameter of the cylinder affected the morphology of the fibers. The present method is applicable for a wide range of conducting substrates, including indium-tin-oxide, glassy carbon, and platinum. The methodology reported here offers a facile and efficient way to fabricate conductive fiber arrays with various morphological features without the use of any templates, opening a door for the design of materials for electronic devices.