Nuclear magnetic resonance and dielectric relaxation investigations of water sorbed by Spherisorb silica
- 1 January 1985
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases
- Vol. 81 (4) , 847-855
- https://doi.org/10.1039/f19858100847
Abstract
The Spherisorb silica/sorbed water system has been investigated at coverages 0.018 ⩽Θ/g H2O g–1 SiO2 ⩽ 0.36 using 1H n.m.r. in the temperature range 190 ⩽T/K ⩽ 300 and also at coverages 0.013 ⩽Θ/g H2O g–1 SiO2 ⩽ 0.033 using dielectric techniques at ambient temperature. In cases where multilayer adsorption occurs there is a discontinuity in the temperature dependence of the n.m.r. linewidth accompanying a freezing phenomenon. Water molecules making up the first loosely packed adsorbed layer (complete at Θ= 0.06 g H2O g–1 SiO2 ) remain mobile at low temperatures at all coverages. Dielectric measurements reveal another discontinuity at a coverage of ca. 0.023 g H2O g–1 SiO2 . Below that coverage the strength of binding of sorbed water increases with decreasing coverage, while at higher coverages additional water leads to a marked increase in the mobility of the first layer.Keywords
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