Interpenetrating polymer network (IPN) hydrogels based on poly(vinyl alcohol) and poly(N-isopropylacrylamide) were prepared by the sequential-IPN method. The IPN hydrogels were analyzed for sorption behavior of water at 35degreesC and at a relative humidity of 95% using a dynamic vapor sorption system, and water diffusion coefficients were calculated. Differential scanning calorimetry was used for the quantitative determination of the amounts of freezing and nonfreezing water. Free water contents in the IPN hydrogel of IPN1, IPN2, and IPN3 were 45.8, 37.9 and 33.1% in pure water, respectively. (C) 2003 Wiley Periodicals, Inc.