Electron spin resonance study on plasma-induced surface radicals of ethylene-tetrafluoroethylene copolymer

Abstract

We have undertaken Ar plasma irradiation on ethylene-tetrafluoroethylene (1:1) alternating copolymer (ETFE) powder, and the radicals formed were studied by electron spin resonance (ESR). The room temperature ESR spectrum of plasma-irradiated ETFE shows a six-line spectrum (sextet) similar to that of polyethylene (PE), due to a small difference in hyperfine splitting constant between p-H and -F atom. Thus, the major radical formed was assigned to the midchain alkyl radical generated by hydrogen elimination. The ESR spectral parameters for a representative sextet deduced from the simulated spectra are as follows: g = 2.0029, 7Va = 2.19mT (1H), Hp = 2.88 mT (2H), and F = 2.80mT (2F). It was also found that the sextet spectrum gradually turned toward a broad single-line spectrum as the plasma duration increased indicating the successive formation of dangling bond sites (DBS) due to the occurrence of cross-linked surface reaction. © 1995, The Society of Polymer Science, Japan. All rights reserved.