Effect of comonomer type and concentration on the equilibrium swelling and volume phase transition temperature of N-isopropylacrylamide-based hydrogels

Abstract

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 deswelling 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°C) for controlled-drug delivery in the human body. © 2008 Wiley Periodicals, Inc.