Self-healable tough supramolecular hydrogels crosslinked by poly-cyclodextrin through host-guest interaction

A new supramolecular hydrogel with superior self-healing and shape memory properties was synthesized via insitu copolymerization of the adamantane-containing monomer N-adamantylacrylamide (Ad-AAm) and monomer acrylic acid (AAc) in the polycyclodextrin (PCD) aqueous solution, where PCD served as the polyfunctional physical cross-linker. The PCD-Ad hydrogels showed strength of 40 kPa with breaking strain of 600%, but small tensile loading-unloading hysteresis and residual deformation benefited from the reversible crosslinking structure. Excellent self-healing property was realized at 70 degrees C and humid condition. The healing percentage reached over 70% after 120 min, which showed enhanced self-healing efficiency compared with the reported supramolecular hydrogels crosslinked by CD and Ad. This may benefit from the polyfunctional PCD crosslinking reagent, which provided more host sites and binding opportunities for the complexation during the self-healing process. Shape memory behavior was also realized through the reversible second crosslinked network by the carboxyl groups of PAAc with Fe3+ ions. The present study provides a new method to improve self-healing ability of the supramolecular hydrogels, which will find the applications in self-healing coating, biomedical materials and soft actuators.