Tough polypseudorotaxane supramolecular hydrogels with dual-responsive shape memory properties

Cyclodextrin-polypseudorotaxane hydrogels have attracted extensive attention for their potential application in biomedical fields. Herein, we develop a facile strategy for the in situ formation of mechanically tough polypseudorotaxane hydrogels through photoinitiated copolymerization of poly(ethylene glycol) methyl ether methacrylate, acrylamide and sodium acrylate in alpha-CD solution at 60 degrees C. For the first time, we manage to screen the host-guest interaction between alpha-CD and PEG before copolymerization in the presence of a temporary hydrogen bonding weakening monomer (acrylamide) at a suitable temperature (60 degrees C). This shielding effect weakens gradually during polymerization, thus leading to the formation of polypseudorotaxane aggregations and a tough physical hydrogel. The hydrogel can bear a large compressive strain (80%) without rupture, and exhibits excellent antifatigue properties. Furthermore, this hydrogel could be endowed with thermal/ascorbic acid activated shape memory performance after being treated with FeCl3 solution. This simple method will contribute to the design and application of smart supramolecular hydrogels.