Water intrusion/extrusion in hydrophobized mesoporous silica gel in a wide temperature range: Capillarity, bubble nucleation and line tension effects

The pressure under which forced intrusion of non-wetting liquid into capillary takes place (intrusion pressure) is a very important parameter for a number of devices using intrusion/extrusion characteristics of porous materials. For molecular springs, dumpers and shock-absorbers based on heterogeneous lyophobic systems (HLS) their efficiency is determined by the pressure of both intrusion and extrusion, the latter being the pressure under which intruded liquid extrudes from the capillary. In this paper the temperature dependence of intrusion and extrusion pressures of a {grafted silica gel + water} HLS is investigated in the 10–150 °С temperature range. An unexpected non-linear temperature dependence of extrusion pressure is obtained. The interpretation of these results is provided with the help of capillary and bubble nucleation theories. The calculations include the line tension effect and contact angles temperature dependence.