DYNAMIC PROPERTIES OF WATER IN POROUS VYCOR GLASS STUDIED BY DIELECTRIC TECHNIQUES

The structure and dynamic properties of water in porous Vycor glass of 40 angstrom mean pore diameter, as well as their changes with tempera ture, were studied by dielectric relaxation spectroscopy and dc conduc tivity measurements. The mobility of water molecules in the pores was reduced compared with that of bulk water by a factor which decreased w ith increasing water content. A significant fraction of water in the f irst monolayer is transformed to a glassy state at about 170 K. The fo rmation of water clusters around primary hydration sites started at ab out 0.02 g(H2O)/g (dry sample) where a transition to long-range connec tivity among water molecules was observed.