A thermosensitive grafted hydrogel was investigated for heating-activated drug release. The hydrogel was created by grafting oligomers of N-isopropylacrylamide-co-acrylamide (AAm) to a poly(2-hydroxyethyl methacrylate), or PHEMA, hydrogel. N-Isopropylacrylamide-co-AAm oligomers were synthesized with a range of compositions to raise the lower critical solution temperature (LCST) above physiological temperature. PHEMA hydrogels with these thermosensitive grafts were synthesized by free-radical solution polymerization, using an acrylated version of the oligomers. The oligomers were characterized for their molecular weight, LCSTs, and rate of response to a change in temperature. With the flexibility in tuning their properties by varying reaction parameters, these oligomers present possibilities in several fields, including drug delivery. The impact of cross-linking agent type and the amount and presence of grafts on the polymer network structure was found by determining the hydrogel mesh sizes. PHEMA gels cross-linked with methylenebisacrylamide had larger mesh sizes than those cross-linked with ethylene glycol dimethacrylate. Increasing amounts of cross-linking agent decreased mesh sizes. LCSTs exhibited by oligomers were slightly lower than those exhibited by polymer gels of the same composition. The grafting reaction was found to have only a slight impact on the hydrogel mesh size. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
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