Construction and deformation mechanism of water-responsive starch-based shape memory emulsion gels

This study developed a water-responsive, starch-based shape memory emulsion gel (SMEG), systematically evaluated its moldability and shape memory performance, and thoroughly analyzed its structural mechanism. By comparing gels prepared from corn starch (CS), potato starch (PS), and tapioca starch (TS), it was found that PS-based shape memory emulsion gel containing 25% (m/v) PS (PS-SMEG (25)) exhibited moderate hardness, good flexibility, and a uniform, dense 3D network, enabling sharp folding without creases and demonstrating excellent mechanical properties. Under 50 °C, PS-SMEG (25) achieved shape fixity and recovery ratios of approximately 100% and stably completed 10 shape memory cycles. Mechanistic studies indicated that the water-regulated dynamic hydrogen-bonded network acts as the reversible phase, fixing the shape through dehydration-induced hydrogen bond strengthening and network densification, and triggering shape recovery via hydration-induced bond dissociation and network relaxation. Macroscopic rheology, microscopic structure, and molecular spectroscopy results showed that the gel undergoes reversible structural evolution of "modulus increase-modulus decrease" and "dense-loose" during deformation, with hydrogen bonds acting as a key "molecular switch" driving the entire water-responsive shape memory cycle. This study provides a fundamental theoretical basis for designing food-derived hydrogels with shape memory properties.