title: Thermal behavior and structure of low-temperature water confined in Sephadex G15 gel by differential scanning calorimetry and X-ray diffraction method.
abstract: The thermal behavior and structure of water confined in Sephadex G15 gel were investigated over a temperature range of 298-173 K at hydration levels, h (= mass of water/mass of dry G15 gel), of 0.24-1.38 by differential scanning calorimetry (DSC) and an X-ray diffraction (XRD) method, respectively. The ice-melting peaks on the DSC curves were deconvoluted to estimate the amounts of three states of water in G15 with h: free water, freezable bound water, and unfrozen water. The X-ray radial distribution functions of unfrozen water at h = 0.24 revealed that the hydrogen-bonded structure of water is largely distorted, due to hydrogen bonding with the surface hydroxyl groups of gel substrates, compared with those of freezable bound water at h = 0.47 and bulk water. A plausible separation mechanism of solutes in gel chromatography was considered from a structural point of view of confined water.
authors.affiliation: Department of Chemistry, Faculty of Science, Fukuoka University, Jonan, Fukuoka, Japan.
authors.forename: Kanae
authors.initials: K
authors.lastname: Ito
authors.forename: Koji
authors.initials: K
authors.lastname: Yoshida
authors.forename: Kikujiro
authors.initials: K
authors.lastname: Ujimoto
authors.forename: Toshio
authors.initials: T
authors.lastname: Yamaguchi