PLASMA COPOLYMERIZATION OF ETHYLENE AND TETRAFLUOROETHYLENE

The 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 almost-equal-to 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 almost-equal-to 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 greater-than-or-equal-to 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 CF(n) moieties in the plasma copolymers or the presence of F atoms in highly fluorinated environments.