Impedance Spectroscopy Study of Composite Thin Films of Hydrated Polyethylene Glycol

A polyethylene glycol (PEG) polymer was synthesized using a dip-coating procedure on 316L stainless-steel (SS) substrate precoated with a primer that consisted of radio-frequency inductively coupled plasma-polymerized di (ethylene glycol) vinyl ether (EO2V). The primer and PEG composite film was studied with profilometer, optical microscope, scanning electron microscope (SEM), and a tape test to evaluate thickness, coverage, morphology, and adhesion, respectively. Response of the PEG composite film to an applied ac voltage was studied as a function of hydration state using impedance spectroscopy (IS). A resistor/capacitor network was used to interpret the impedance spectra. Electrical capacitance of the PEG film decreased with an exponentially decaying term as dehydration progressed. PEG-film capacitance decay was consistent with a model describing water molecules diffusing through the PEG film.