GAS SELECTIVE PLASMA POLYMERIZATION MEMBRANE

Two silicon- and six fluorine-containing compounds were chosen as monomers and plasma-polymerized for preparation of permselective membranes. The oxygen and nitrogen permeability coefficients and separation factor (P(O2)/P(N2)) of the plasma films deposited on Millipore membranes were discussed. Plasma polymers deposited from silicon-containing compounds, hexamethyldisiloxane and hexamethyldisilane, and from aliphatic fluorine-containing compounds, tetrafluoroethylene, and perfluoromethylcyclohexane, are not adequate materials for oxygen-selective membrane. Plasma polymers deposited from aromatic fluorine-containing compounds, perfluoro-benzene, pentafluorobenzene, trifluoro-benzene, and ditrifluoromethyl-benzene, however, are adequate materials for oxygen-selective membranes. The CF4 addition into the aromatic fluorine-containing compounds leads to the formation of plasma polymers with improved separation factor (P(O2)/P(N2)). The CF4 addition brought about changes in fluorinated carbon distribution, and contributed to the formation of crosslinkings in polymeric chains. The crosslinkings might restrict the thermal motion of polymeric chains and might improve the separation factor.