High pressure intrusion of water and LiCl aqueous solutions in hydrophobic KIT-6 mesoporous silica: Influence of the grafted group nature

Abstract High pressure intrusion-extrusion of water and LiCl aqueous solutions in KIT-6 mesoporous silica grafted with alkyl or perfluoroalkyl groups have been studied for absorption of mechanical energy. The “grafted KIT-6 – LiCl solution” systems demonstrate a shock absorber behavior with a large hysteresis between intrusion and extrusion curves and partially irreversible intrusion in the first intrusion-extrusion cycle. The samples of KIT-6 with perfluroalkyl grafting demonstrate higher values of intrusion pressure in comparison with ones grafted with alkyl groups, but lower intruded volume. It has been found that the intrusion of LiCl solutions leads to a considerable increase of intrusion pressure, particularly pronounced in the case of the samples grafted with perfluoroalkyl groups. This increase is higher than one expected from the Laplace-Washburn equation. When salt concentration increases, the intrusion becomes more reversible in the case of alkyl grafting, but slightly less in the case of perfluoroalkyl one.