β ‐Cyclodextrin hydrogel incorporating hydrophobically modified poly( N ‐isopropylacrylamide) for a temperature‐dependent release

Hydrogels exhibiting a temperature‐dependent release were prepared by incorporating hydrophobically modified poly( N ‐isopropylacrylamide) (HmPNIPAM) into β ‐cyclodextrin hydrogels ( β ‐CD hydrogels). The specific loading of HmPNIPAM was about 0.0069 g HmPNIPAM/g β ‐CD hydrogels. The incorporation of the polymer was qualitatively conformed by FT‐IR spectroscopy and SEM. The percent release of blue dextran in 24 hr at 20°C (about 77%) was markedly higher than those obtained at 35°C and 45°C (about 53 and 55%, respectively). At the higher temperatures, the volume of the hydrogel could decrease upon the thermal contraction of HmPNIPAM, leading to a smaller mesh and a suppressed release. In fact, the swelling ratio in 24 hr at 35°C and 45°C (about 396% and 405%, respectively) was obviously lower than that obtained at 20°C (about 465%). Copyright © 2011 John Wiley & Sons, Ltd.