Novel temperature-sensitive poly[N-isopropylacrylamide-co-2-hydroxyethylacrylate] [P(NIPAAm-HEAc)] colloidal crystals containing β-cyclodextrin (β-CD) were prepared. These reversibly tunable supramolecular inclusion complexes display brilliant colors, due to the self-assembly of several structured nanoparticles to form crystal structures. The hydrogels displayed rainbow colors upon the variation of the β-CD concentration and can be made either visible or invisible by simply changing the temperature. The inclusion complexes were characterized using NMR spectroscopy, laser light scattering, UV–visible spectroscopy, and viscometer measurements. Compared with the conventional poly(N-isopropylacrylamide) gel, the β-CD-incorporated hydrogels in aqueous solution showed a lower critical solution temperature of about 57°C, which can be attributed to the hydrogen bonding between P(NIPAAm-HEAc) included in β-CD and water, which is enhanced by the hydrophilic groups of β-CD. The use of these materials as drug carriers was also evaluated by making use of their thermo-responsive behavior. The release time of a model drug, 5-fluorouracil (5-FU), from the novel inclusion complexes was prolonged in comparison to that from P(NIPAAm-HEAc) without β-CD. The significance of the present drug delivery system is the mixing of the gel and drug without any chemical reaction at room temperature, resulting in a gelled drug depot for slow and controlled release. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
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