Tough and rubber-like physically crosslinked hydrogels were prepared by blending of concentrated aqueous solutions of poly(vinyl alcohol) (PVA) and poly(sodium L-glutamate) (PSLG) in an autoclave under 2 atm pressure at 120 degrees C. There are three types of water in every blend hydrogel, i.e. free water, unfrozen water (namely bound water), and frozen bound water. Unfrozen water content increases with increasing PSLG content because of the increase in the number of the ionic -COONa group, which has many bonding sites with the water molecular. Heat of thawing per unit weight of water, i.e. free and frozen bound waters, not containing unfrozen water (Delta H-W), estimated for hydrogels having various water contents, was obtained by dehydration and was smaller than that of free water. Spin lattice relaxation time (T-1), obtained by pulsed nuclear magnetic resonance measurement, decreases with increasing PSLG content. These results for Delta H-W, and iri are caused by the interaction between water and ionic -COONa groups of the PSLG molecules.