Impact-Resistant Hydrogels Via Quaternary Ammonium-Regulated Networks.

Hydrogels are increasingly explored as structural candidates for impact-mitigation and protection systems because of their biocompatibility, softness, and design versatility. However, conventional hydrogels typically suffer from inadequate mechanical properties and environmental instability, which severely hamper their practical applications. Here we report the use of quaternary ammonium-regulated networks to overcome these limitations, without the need for cumbersome postprocessing or high energy consumption. The approach enables controlled structural organization in polymers containing regularly spaced polar groups (e.g., polyvinyl alcohol, poly(acrylic acid), and polyacrylamide), transforming large, densely packed rigid domains into dynamic, adaptable supramolecular architectures. This arises from strong quaternary-ammonium-polymer associations that restrict local chain mobility and promote ordered segmental packing. Consequently, by tuning polymer composition, the hydrogels have widely tunable mechanics from brittle to ductile behavior, with ultimate stresses of 32.9-101.9 MPa, strains of 29%-1670%, and toughness values of 22.7-434.1 MJ m- 3. They also show exceptional impact-resistant performance (426.7 MPa), combined with high energy dissipation (96.02%) and puncture resistance (1.3 J), which compares favorably to those of other tough hydrogels and even natural materials. The presented strategy is generalizable to other polymers, and could expand the applicability of structural hydrogels to more mechanically demanding conditions.