Structure of water and ice in poly-N,N,-dimethylacrylamide hydrogel

Sekine, Yurina   ; Fukazawa, Tomoko*; Yamauchi, Hiroki   ; Songxue, C.*; Chakoumakos, B.*; Fernandez-Baca, J. A.*; Fukazawa, Hiroshi

Neutron diffraction data of deuterated poly-N,N,-dimethylacrylamide (PDMAA) hydrogel were measured at temperatures of 10 - 290 K in order to investigate the structure and properties of water in the hydrogel. Diffraction peaks observed below 270 K indicate the existence of a solid ice in the hydrogel. The positions of some peaks from the ice are lower than those in ordinary hexagonal ice (Ih). The lower shifts of the peaks indicates that the lattice constants of the c-axis in the ice are about 0.3% higher than those in ice Ih, whereas those of the a-axis are almost consist. The results show that bulk of a low-density ice crystal exists in the PDMAA hydrogel. The water molecules, which have a significant interaction with the polymer chains, play an important role in the chemical and mechanical properties of the hydrogel.