A new IPN hydrogel poly(N-vinyl pyrrolidone-co-β-hydropropyl acrylate)/poly(acrylic acid) was synthesized.and its temperature and pH sensitive behavior was studied.In acidic medium the swelling ratio (SR) of this hydrogel slumps suddenly and drops quickly with temperature rising due to the hydrogen bond formation between PNVP and PAA.In alkaline medium
the SR of the IPN hydrogel rises as the temperature is raised.