SURFACE FREE-ENERGY CHARACTERISTICS OF POLYFLUORINATED SILANE FILMS

A homologous series of [(perfluoroalkyl)ethyl]silane films was produced on glass and on fused quartz by spontaneous formation from solutions of the corresponding trichlorisilanes. The low energy of the film surfaces of the higher homologues indicates that the silane molecules are closely packed and highly oriented perpendicular to the surface, exposing mainly the -CF3 groups on the surface. The surface energy of the films is a function of the length of the perflurinated chain of the molecules. The surface energy is near a minimum of about 11 dyn/cm with a perfluorinated chain of four carbon atoms, decreasing only slightly with longer chains. There was no significant difference in surface energy between films formed on glass or on quartz. The surface energy of the films did not change upon exposure to water, which indicates that neither deterioration nor reversal of the orientation of the molecules took place.