Water Condensation in Hydrophobic Nanopores

摘要

There are many intriguing situations in everyday life where water is confined to spaces of nanoscopic dimensions by hydrophilic as well as hydrophobic substrates such as in colloidal particles,protein cavities,and inorganic solid walls.Fundamental interest stems from the fact that the properties of confined water are believed to be very different from those of the corresponding bulk fluid at the same temperature and chemical potential.Recently,it was shown that storage or dissipation of mechanical energy could be achieved by forced intrusion/extrusion of water into/from hydrophobic porous materials.Intrusion of water into silicalite-1 zeolite at a hydraulic pressure of about 100MPa at room temperature results in its condensation.A spontaneous capillary evaporation (drying) took place upon release of the pressure.Similar behavior was observed very recently in the case of hydrophobized MCM-41 mesoporous materials.Interestingly,the intrusion/extrusion cycle was accompanied by a hysteresis effect in the latter case,but not in the former one.Situations were also encountered in which no extrusion of water took place upon release of the pressure (zeolite (3 and wide-pore MCM-41).