Acceleration of Deswelling of Poly(N-isopropylacrylamide) Hydrogel by the Treatment of a Freeze-Dry and Hydration Process
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The deswelling rate of a thermally-sensitive gel consisting of poly(<i>N</i>-isopropylacrylamide) crosslinked by 4% <i>N</i>,<i>N</i>′-methylenebisacrylamide (MBA) was accelerated at above the lower critical solution temperature (LCST) by the treatment of a freeze-dry and hydration process (freeze-dry treatment); it was roughly 10<sup>2</sup> times faster than the gel without a freeze-dry treatment. The values of the apparent activation energy (<i>E</i><sub>a</sub>’s) for the conventional gel crosslinked by 2 and 4% MBA was roughly 140 kJ mol<sup>−1</sup> each, and those for freeze-dry treated gel crosslinked by 2, 4, and 10% MBA were 24, 25, and 12 kJ mol<sup>−1</sup>, respectively. An SEM photomicrograph showed that the freeze-dry treatment made the gel porous. The freeze-dry treated gel exhibited a weaker shrinking force, and showed easy expansion compared with the conventional gel. An expansion of the diffusion area of water and a decrease of the thickness of the surface layer for a macroporous gel could be the reason for the increase in the deswelling rate.
- Bulletin of the Chemical Society of Japan
Bulletin of the Chemical Society of Japan 70(6), 1289-1295, 1997-06-15
The Chemical Society of Japan