Regulating the self-assembly of PS-b-PNIPAm block copolymers enables dual-responsive shape memory hydrogel

In this study, we developed a poly(styrene-b-N-isopropyl acrylamide) (PS-b-PNIPAm) block copolymer-incorporated hydrogel with cooling/water dual-responsive shape recovery performance. Three kinds of PS-b-PNIPAm block copolymers with different chain lengths of PNIPAm were prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization, and the block copolymers could self-assemble into micelles with PNIPAm as the outer layer in water. Hydrogels were then prepared by introducing the micelles formed by the block copolymers into the polyacrylamide (PAM) network. The collapse of PNIPAm chains could be promoted by both temperature and salt, which acted as temporary crosslinks to stabilize temporary shapes, enabling cooling- and water-stimulated shape recovery. Moreover, fluorescent information could be encoded on the surface of the hydrogel and encrypted by the shape changes of the hydrogel during the shape fixing process, with the information revealed under UV irradiation after the shape recovery process, achieving information security. This approach could accelerate the evolution of shape memory hydrogels and broaden their applications across diverse fields.