Tough and Fast-Responding Fe3+-Coordinated Poly (Acrylic Acid -N-Isopropyl Acrylamide) Shape Memory Hydrogels

Hydrogels with programmable shape memory hold great promise for applications in soft robots, smart medical devices, etc., but the preparation of tough and fast-responding shape memory hydrogels remains challenging. In this work, Poly (acrylic acid -N-isopropyl acrylamide) (3:1)-Fe³⁺ (P(AA-NIPAM)(3:1)-Fe³⁺) hydrogels are obtained by monomer copolymerization and ionic coordination, which exhibited tough mechanical properties with a maximum tensile strength of 2.48 ± 0.08 MPa and a maximum elongation of 338.5 ± 19.6%. The hydrogel also demonstrated a good shape memory effect, with the hydrogel curled into a spiral shape recovering to 71.1% ± 5.9% in 30 s under the swelling effect of water, and the convoluted structure recovering to 95% in 4 s. The shape memory hydrogels prepared based on this method will provide an important reference value for the development of higher performance shape memory hydrogels.