X-RAY AND NEUTRON-SCATTERING STUDIES OF THE STRUCTURE OF WATER IN A HYDROGEL

The structure of water absorbed in polyHEMA is studied by X-ray diffraction in the vitreous state at 77 K as well as in the liquid state at room temperature. Molecular packing at the level of the first neighbors is found similar to that in bulk water but a distortion is observed at the level of the second neighbors which is attributed to the bending of the H bonds. From the widths of the Bragg peaks of the crystalline ices from the small-angle neutron scattering results, we deduce that the pore size and the interpore distance in the swollen polyHEMA are smaller than 30 angstrom.