Thermal Behavior, Structure, and Dynamic Properties of Water Confined in Polymer Gel Sephadex G15


Kanae Ito


K. Ito, K. Yoshida, K. Ujimoto, M.-C. Bellissent-Funel, T. Yamaguchi

Author Affiliation: 

Department of Chemistry, Faculty of Science, Fukuoka University, Nanakuma, Jonan, Fukuoka 814-0180, Japan Laboratoire Leon Brillouin (CEA-CNRS), CEA Saclay, 91191 Gif-sur-Yvette Cedex, France Center for Polymer Studies and Department of Physics, Boston University, Boston, Massachusetts 02215, USA


The thermal behavior, structure, and dynamic properties of water confined in polymer gel Sephadex G15 were investigated over a temperature range of 298-173K as a function of hydration level (g H2O/g dry gel) by differential scanning calorimetry (DSC), X-ray diffraction (XRD), and quasi-elastic neutron scattering (QENS) and neutron spin echo (NSE) measurements. The DSC data showed that there are three states of water in G15 gel: free water, freezable bound water, and unfrozen water. The X-ray radial distribution functions revealed that the tetrahedral-like hydrogen bonded network of confined water is largely distorted, compared with the bulk water. The QENS data showed that the water molecules perform local motions characterized by a diffusion coefficient of (0.65 +/- 0.05) x 10-5cm2s-1 within a sphere with a radius of 4.4 Angstrom. The Arrhenius plots of the relaxation time of water gave an activation energy of 44.2 +/- 1.5 kJmol-1, which is somewhat larger than the value of 15-36kJmol-1 of capillary condensed water confined in mesoporous silica MCM-41 C10 (pore diameter 21 Angstrom). The present findings suggest that water molecules in G15 gels are strongly bound to the hydroxyl groups of the gel matrix.