Rigid and Strong Thermoresponsive Shape Memory Hydrogels Transformed from Poly(vinylpyrrolidone-co-acryloxy acetophenone) Organogels

Shape memory hydrogels (SMHs) have a wide range of potential practical applications. However, the mechanically weak and soft nature of most SMHs strongly impedes their applications. Here, we report a novel kind of thermal-responsive SMH with high tensile strength and high elastic moduli. Organogels are first prepared by the copolymerization of a hydrophilic monomer N-vinylpyrrolidone (NVP) and a hydrophobic monomer acryloxy acetophenone (AAP) in N,N′-dimethylformamide (DMF) solutions, and then, poly(vinylpyrrolidone-co-acryloxy acetophenone) [poly(NVP-co-AAP)] hydrogels are obtained by solvent exchange with water. Because of the strong and reversible hydrophobic association and π–π stacking of acetophenone groups, the poly(NVP-co-AAP) hydrogels exhibit tensile strengths up to 8.41 ± 0.83 MPa and Young’s moduli up to 94.2 ± 1.3 MPa, which are more than 1 or 3 orders of magnitude higher than those of the organogels, respectively. The poly(NVP-co-AAP) hydrogels exhibit good shape memory behaviors, with a com...