Interpenetrating polymer network (IPN) hydrogels based on poly(propylene glycol) diacrylate macromer and poly(acrylic acid) (PAAc) were prepared by UV irradiation and characterized by swelling in water. The swelling behavior of these IPNs was analyzed in buffer solution at various temperatures. Swelling ratios of all IPNs were relatively high and showed reasonable sensitivity to temperature. Hydrogels showed both positive and negative swelling behavior depending on PAAc content. PA22 and PA13 showed positive and PA31 showed negative temperature-sensitive swelling behavior. (C) 2003 Wiley Periodicals, Inc.