Dielectric Relaxations in Plasma-Polymerized Hydrocarbons and Fluorocarbons

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Abstract
The dielectric behavior of plasma-polymerized ethylene (PPE), ethylene/acetylene (PPEA), ethane/vinyl chloride (PPEVC) and tetrafluoroethylene (PPTFE) was studied over a frequency range of 102 to 105 Hz between -150 and 100°C. After exposure to the atmosphere, each of the polymers exhibited a pronounced loss peak. This relaxation process was designated as the γpprocess, and was attributed to the local mode motion of several molecular segments. The average activation energy for all four polymers was found to be 13.8 kcal/mole. It was proposed that oxidation introduces carbonyl groups into the nonpolar polymer chain. The added polar carbonyl groups then act as tracers to render the molecular motions observable by dielectric measurements. The presence of these carbonyl groups was confirmed by concomitant IR spectroscopic determinations. Comparison of the experimental data with the Kirkwood-Froelich theory was found to be satisfactory.