Plasma copolymerization of ethylene and tetrafluoroethylene

Abstract

AbstractThe plasma copolymerization of ethylene (ET) and tetrafluoroethylene (TFE) was investigated by means of IR and XPS analyses. The deposition rates for plasma ET/TFE copolymers, when plotted versus mol % TFE in the feed gas, gave a concave‐downward curve situated above the straight‐line joining the deposition rates for the respective plasma polymers, PPET and PPTFE, with the maximum rate at ∼ 70‐80 mol % TFE. This result, coupled with the finding that normalized absorbances of the CH and CF IR bands of ET/TFE copolymers had maxima at ∼ 20 and 80 mol % TFE, respectively, indicated a positive interaction between ET and TFE such that each monomer “sensitized” the plasma copolymerization of the other. As analyzed by XPS, CF groups dominated over CF2 and CF3 groups at 5‐70 mol % TFE, but at ≥ 80 mol % TFE, these moieties approached the relative proportions in PPTFE (CF2 > CF3 > CF). The plot of F/C ratio versus mol % TFE was concave‐upward and situated below the hypothetical straight‐line plot representing noninteracting, independent polymerization of ET and TFE, while the % F in the plasma copolymers was linear with mol % TFE. The F1s mean binding energies of the ET/TFE plasma copolymers, which increased monotonically with % F, were consistently higher than those for several commercial polymers of fluorinated olefins at comparable values of % F. This result suggested clustering of CFn moieties in the plasma copolymers or the presence of F atoms in highly fluorinated environments. © 1992 John Wiley & Sons, Inc.