Reactive macromolecular micelle crosslinked highly elastic hydrogel with water-triggered shape-memory behaviour

Highly stretchable hydrogels based on the micellar copolymerization technique often dissolve in water; they may also become fragile or not exhibit their initially good mechanical performance when submerged in large amounts of water. In addition, the shape-deformation and shape-recovery processes of most reported shape-memory hydrogels need to be carried out at high temperatures. As yet, there have been no published reports on hydrogels which are both highly resilient and have water-responsive shape-memory properties. In this work, a novel, highly elastic polyacrylamide-based hydrogel was developed based on the micellar copolymerization technique using a polymerizable macromolecular micelle with hydrophobic cores locked by hydrogen bonds as a multifunctional crosslinker. The equilibrium water-swelling micelle crosslinked hydrogels still showed highly stretchable behaviour (elongation at break >700%) and even better resilience (almost no hysteresis and residual strains) than the as-prepared hydrogels. Together with the advantages of the highly elastic properties of the hydrogels and the dehydration-induced glass transition of the polyacrylamide network, the hydrogels also have a water-responsive shape-memory behaviour, which can be realized under mild and “green” conditions, i.e., in air and water at room temperature.