Direct current gas–liquid phase pulsed plasma polymerization of polypyrrole under atmospheric pressure

In this study, an atmospheric-pressure nanosecond impulse discharge initiated above the pyrrole microemulsion surface is applied to polymerize pyrrole and obtain a polypyrrole film. The films obtained under different number of plasma discharge times and duration of argon gas input time are investigated using a field emission scanning electron microscope. Results show that the roughness and thickness of the polypyrrole film can be tuned by controlling discharge times and the gas feed time. Four-point sheet resistance measurements of the films reflect that those with a smoother and more complete surface have better electrical conductivity. The films are identified as polypyrrole by Fourier-transform infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectrometry. Also, N₂ is a critical factor in polymerizing polypyrrole and the gas–liquid plasma polymerization mechanism, which has three steps, is discussed.