Neutron diffraction study of chemically cross-linked hydrogels

Sekine, Yurina   ; Chi, S.*; Fernandez Baca, J.*; Fukazawa, Tomoko*; Fukazawa, Hiroshi

Neutron diffraction profiles of high and low- DO-content poly-N,N,-dimethylacrylamide (PDMAA) hydrogels were measured from 100 to 300 K to investigate the structure and properties of water in hydrogels. For high DO content hydrogel, strong sharp peaks are observed in 100 to 250 K. The feature of the peaks is similar to that of hexagonal ice (ice Ih). For low DO-content hydrogel, a broad band is observed at temperatures less than 220 K. The result indicates the existence of amorphous ice in the hydrogel. During the heating process, diffraction peaks from ice crystals appear in the profiles. The peaks indicate that cubic ice and hexagonal ice exist at temperatures above 220 K. We first obtained structure parameters of these ices in the hydrogel, which indicate the existence of low-density ice in the hydrogel.