ADSORPTION CHARACTERISTICS OF SILICA-GELS TREATED WITH FLUORINATED SILYLATION AGENTS

Branched-chain polyfluorosilane (monochlorodimethyl trifluoromethyl)-5 ,5,6,6,7,7,7-heptafluoroheptyl)- bounded silica gels were prepared. Th e surface properties of the silica gels modified with various organic silanes were evaluated by the adsorption density of polar and nonpolar gases calculated from adsorption isotherms of nitrogen, carbon dioxid e, and normal butane gases, The polyfluorocarbon-bonded silica gel sur face was found to be both hydrophobic and oleophobic in nature, wherea s the hydrocarbon-bonded silica gel surface was characterized only as hydrophobic, The trifunctional fluorinated silane provides the silica gel surface with a more hydrophilic nature than the monofunctional sil ane because of the formation of a denser polymeric coating layer with a larger number of silanols. (C) 1997 Academic Press