Effects of Precursor Type on Plasma Discharge Characteristics and Polypyrrole Nanostructured Film Properties Using Atmospheric-Pressure Plasma Jets

Abstract

The role of precursor chemistry in determining the charge-transport characteristics of APPJ-derived polypyrrole (PPy) nanostructured films was assessed using two precursor formulations. One consisted of untreated liquid pyrrole monomer (Type I), whereas the other was a liquid plasma-treated (PT) pyrrole polymer (Type II) that had undergone plasma pretreatment. Particular attention was given to the relationship between precursor characteristics, film morphology, and the resulting electrical performance, especially the formation of a compact and highly interconnected polymer network. The OES and ICCD observations indicate that the Type II precursor undergoes more effective plasma activation, which is associated with enhanced electron production during ionization processes while retaining plasma-induced oligomer characteristics. The resulting increase in plasma excitation promotes the generation of reactive excited species, facilitating the chemical reactions required for subsequent PPy polymerization. In addition, the morphological and chemical analyses using field emission-scanning electron microscopy (FE-SEM), Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS) revealed distinct differences in the Type II-derived PPy layer. The film developed a compact and highly interconnected nanoscale architecture, accompanied by characteristic C–N and C=C bonding features identified from the spectroscopic analysis. These structural and chemical characteristics are likely responsible for maintaining continuous charge-transport pathways within the polymer network. Consequently, the Type II-based film retained its electrical conductivity more effectively during prolonged exposure to ambient conditions than the corresponding Type I film.