Highly Elastic Supramolecular Hydrogels Using Host–Guest Inclusion Complexes with Cyclodextrins

Supramolecular hydrogels, which are cross-linked via host–guest interactions, show high-performance physical properties, such as elasticity and toughness. Herein we prepare a supramolecular hydrogel without chemical cross-linker. The supramolecular hydrogel was prepared by polymerization of the inclusion complexes between β-cyclodextrin acrylamide and adamantane acrylamide monomers. The β-cyclodextrin–adamantane gel (βCD–Ad gel) shows a high stretching property (990%). The initial strain (0%) is restored in several minutes for a βCD–Ad gel stretched to 180% of the initial strain without altering the physical history. However, chemically cross-linked poly(acrylamide) does not show the reversible stretching property. These results indicate that host–guest interaction inside the supramolecular hydrogel plays an important role in the shape recovery properties.