Robust Heterogeneous Hydrogels with Dynamic Nanocrystal-Polymer Interface

A kind of novel heterogeneous composite hydrogel with dynamic nanocrosslinkers is designed, which is built via the preorganized host-guest interaction on the surface of cellulose nanocrystals. The reversible beta-cyclodextrin/adamantane conjunctions and their gradual dissociation on the nanocrystal-polymer interface guarantee the compressibility and stretchability of the composite hydrogels. While the sacrificed toughening mechanism can be rebuilt in the as-prepared hydrogels, it fails to be regenerated in the swollen hydrogels. This fact is originally due to the extreme mechanical contrast between rigid nanocrystals and the flexible polymer phase. This heterogeneity is largely amplified by the swelling process: poly-mer chains are prestretched between nanocrosslinkers and generate residual stress on the dynamic nanocrystalpoly-mer interface. Thus, this swelling-induced heterogeneity resists the reassociation of the sacrificed beta-cyclodextrin/adamantane complexes. Furthermore, the unstable nanocrystalpolymer interface induces the crack propagate along the nanocrosslinker surface, which remarkably retards the crack propagation during the stretch.