Temperature-controlled erosion of poly(N-isopropylacrylamide)-based hydrogels crosslinked by methacrylate-introduced hydrolyzable polyrotaxane

Biodegradable hydrogels for temperature-controlled erosion were prepared by co-crosslinking N-isopropylacrylamide (NIPAAm) and methacrylate (MA)-introduced polyrotaxane (PRX) in which many α-cyclodextrins (α-CDs) are threaded onto a poly(ethylene glycol) chain capped with bulky end-groups via ester linkages. The amount of MA attached to hydroxyl group of α-CDs in PRX could be varied by the feed ratio of GMA and PRX. The prepared hydrogels were transparent below lower critical solution temperature (LCST) of PNIPAAm matrix (32 °C). By elevating temperature above the LCST, water contents were slightly decreased, and the hydrogels became opaque. Elevating temperature in an aqueous condition above the LCST led to dehydration of the PNIPAAm matrix, which accompanies α-CD sliding to expose the ester linkage to the medium and enhances erosion of the hydrogels.