Benzene Adsorption on Nanoporous Silica Gels with Grafted Polyfluoroalkyl Layers and the Wettability

Features of the benzene adsorption in polyfluoroalkyl layers of different structures grafted on surfaces of silica gel (SG) are studied using gas chromatography, static adsorption, and diffuse reflectance IR spectroscopy. After modification, Henry’s law constants determined from the gas chromatography data and the static benzene adsorption values fall in the order SG > SG–F(III) > SG–F > SG–iso-F(III), where samples SG–F(III), SG–F, and SG–iso-F(III) are produced using silanes n‑C6F13(CH2)2SiCl3, n‑C6F13(CH2)2Si(CH3)2Cl, and iso-C3F7(CH2)2SiCl3, respectively. It is found that the energy characteristics of adsorption of benzene and other hydrocarbons on the SG–F(III) sample with the linear trifunctional modifier are 3–7 kJ/mol higher than the respective characteristics determined on the initial support. The contact angles for nanoporous silica gels with polyfluoroalkyl layers are calculated from desorption data in the region of the capillary condensation hysteresis of the benzene adsorption isotherms.