How Anionic Dopants Impact the Electrochemical Additive Manufacturing of Polypyrrole

Abstract

Electrochemical additive manufacturing (ECAM), based on meniscus-guided deposition, is an emerging technique for the fabrication of conducting polymers. The ECAM fabrication of polypyrrole entails the electrochemical polymerization of pyrrole monomers and additive manufacturing of polymers. Herein, we investigate the 2-naphthalene sulfonic acid sodium salt (NSA-a), sodium naphthalene-2,6-disulfonate (NSA-b), and 4,5-dihydroxy-1,3-benzenedisulfonic acid disodium salt (Tiron) as anionic dopants for the ECAM processing of polypyrrole. The analysis of the dopants, encompassing the electrochemical tests and electron microscopy measurements coupled with energy-level calculations, provides an insight into the influence of their structure and functional groups on polypyrrole depositions. The increase in the charge/mass ratio of the dopant results in lower deposition potential, higher deposition rate, and reduced particle agglomeration. Atomic force microscopy tests reveal that the employment of Tiron demonstrates improved deformation tolerance with stronger adhesion due to the chelating properties. The high electronic conductivity of Tiron-doped polypyrrole is attributed to multiple −SO3 – groups, which enhance the interchain mobility of charge carriers. Tiron-doped polypyrrole micropillars are successfully produced via pulling of the meniscus. The findings present an opportunity for the optimization and engineering of ECAM fabrications.