INTRUSION AND EXTRUSION OF WATER IN HYDROPHOBIZED POROUS SILICA

The processes of the intrusion and extrusion of water in a porous sili ca matrix preliminarily subjected to the chemical modification by n-al kylchlorosilanes were studied. It was shown that the pressures of intr usion and extrusion of water from the pore space monotonically increas e when the length of the grafted alkyl chain increases and the mean ra dius of the pores of silica decreases. The hysteresis and equilibrium contact angles for the wetting of the surface of modified silica by wa ter were measured; it was shown that the values of these angles increa se with increasing length of the grafted alkyl chain. The maximum valu es of the contact angle, i.e., the maximum hydrophobicity of the surfa ce, were obtained in the case of grafted layers with n-hexadecyl and n -octyl groups.