Synthesis, characterization, and drug release properties of poly(N-isopropylacrylamide) gels prepared in methanol-water cononsolvent medium

Poly(N-isopropylacrylamide) (PNIPAM) hydrogels were simply prepared by free radical polymerization in different methanolwater mixture. A scanning electron microscopy study revealed that the freeze-dried hydrogels were macroporous. The swelling ratios in water at 20 degrees C of the resulting hydrogels followed the order: X0.43>X0.21>X0.76 approximate to X0.57>X0.31>X0.13>X0.06>X0, where Xm denotes a gel prepared in a methanolwater mixture with m mole fraction of methanol (xm). Below the lower critical solution temperature, the swelling ratio values of all of the hydrogels gradually decreased with the increase in the temperature. The complete collapse of the PNIPAM chain of all the gels occurred at about 38 degrees C, whereas the same was observed at about 35 degrees C for the conventional gel prepared in water. The swelling ratio values of all the PNIPAM gels in the methanolwater mixtures with different xm values at 20 degrees C passed through a minimum in the cononsolvency zone. The deswelling rates of the hydrogels decreased in the following order: X0.43> X0.31> X0.21> X0.57> X0.76 approximate to X0.13> X0.06> X0. The reswelling rates of these hydrogels decreased in the following order: X0> X0.31> X0.06 X0.13 > X0.76> X0.57> X0.21> X0.43. The release rates of the Tramadol Hydrochloride drug at 37 degrees C from the drug-loaded hydrogels were almost same for all of the hydrogels. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012