The effect of incorporating a hydrophilic monomer into poly(N-isopropylacrylamide) (polyNIPA) hydrogels on the equilibrium swelling and the volume phase transition temperature is reported here. A nonionizable monomer (acrylamide) and three ionizable monomers (itaconic acid, 2-ethoxyethyl monoitaconate, and 2,2-(2-ethoxyethyl) monoitaconate) were studied. Hydrogels with larger swelling capacity than that of the polyNIPA hydrogel were obtained. With the exception of the hydrogel containing 2,2-(2-ethoxyethyl) monoitaconate, which did not exhibit the swelling phenomena, the rest showed a volume phase transition. The hydrogels containing 85 wt % acrylamide and 15 wt % comonomer presented the higher shrinking ratio. For some compositions, the T-c of the polyNIPA hydrogel was within the desired temperature range (38-41 degrees C) for controlled-drug delivery in the human body. (c) 2008 Wiley Periodicals, Inc.