Quasi-Elastic Neutron Scattering Study of Water Confined in Periodic Mesoporous Organosilicas

Abstract

Water confined in nanoscale space behaves significantly differently from bulk water. We have applied the Quasi-Elastic Neutron Scattering technique to investigate diffusive properties of water confined in porous silicate coated with hydrophobic organic functional groups, at two different levels of hydration. The measurements were performed over a wide range of temperatures, and although we cannot exclude subdiffusion, the data are more easily understood from a distribution in the diffusive dynamics ranging from static water monolayer at the pore surface to much greater mobility towards the pore centre. There is some evidence for a local diffusive motion with an effective radius of about 3.5 A. The overall diffusion constants are significantly less than bulk water over the same temperature ranges.