Impact‐Resistant Hydrogels by Harnessing 2D Hierarchical Structures

Abstract With the strengthening capacity through harnessing multi‐length‐scale structural hierarchy, synthetic hydrogels hold tremendous promise as a low‐cost and abundant material for applications demanding unprecedented mechanical robustness. However, integrating high impact resistance and high water content, yet superior softness, in a single hydrogel material still remains a grand challenge. Here, a simple, yet effective, strategy involving bidirectional freeze‐casting and compression‐annealing is reported, leading to a hierarchically structured hydrogel material. Rational engineering of the distinct 2D lamellar structures, well‐defined nanocrystalline domains and robust interfacial interaction among the lamellae, synergistically contributes to a record‐high ballistic energy absorption capability (i.e., 2.1 kJ m −1 ), without sacrificing their high water content (i.e., 85 wt%) and superior softness. Together with its low‐cost and extraordinary energy dissipation capacity, the hydrogel materials present a durable alternative to conventional hydrogel materials for armor‐like protection circumstances.