A comparison of the properties of vicinal water in silica, clays, wood, cellulose, and other polymeric materials.

The properties of water are known to be significantly modified by propinquity to solid surfaces. This author has previously measured some thermodynamic properties of water in silica gel pores and offered a statistical thermodynamic model for vicinal water that is apparently able to account successfully for the observed properties of water in silica pores. This model suggests that hydrogen bonding between water molecules is enhanced by propinquity to solid surfaces. The experimental work suggests that the structural modification extends at least to distances approaching 5 nm from the surface. In addition to the work of the present author, Low has conducted an extensive study of the thermodynamic properties of water in clays. Low's results are remarkably similar to those of the present author, suggesting that the "state" of vicinal water in both systems is similar. In this paper, the properties of water adjacent to several surfaces are compared. The properties of water near cellulosic surfaces, including wood, are compared to those in silica. It appears that the properties of vicinal water adjacent to dissimilar surfaces are nearly identical to those in silica gel. Significantly, it appears that the notion of "structure breaking" surfaces suggested earlier by Goring and the notion of dense water near surfaces discussed, for instance, by Stamm are, in fact, inconsistent with the available thermodynamic data, despite their rather frequent mention in the wood and paper literature.