Water insertion in hydrophobic porous oxides

We have studied the synthesis of porous hydrophobic systems made from silica and zirconia. The silica systems have been grafted with alkyl-chlorosilanes. Alternative hydrophobic systems were also obtained by synthesis of colloidal monoclinic zirconia grafted with various alkyl phosphonates. The mechanism and the density of grafting were studied by solid state MAS NMR and nitrogen adsorption isotherms. The bulk thermodynamic properties of water are strongly dominated by the interfacial interactions at the surface of these porous solids. The penetration of water in these porous systems was studied by high pressure intrusion of water (water porosimetry between 0 and 100 MPa) into the hydrophobic pores. The amazing mechanical behavior of such water-porous body mixtures can find interesting applications for mechanical energy storage and dissipation.