Robust Heterogeneous Hydrogels with Dynamic Nanocrystal-Polymer Interface

Abstract

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 β-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: polymer chains are prestretched between nanocrosslinkers and generate residual stress on the dynamic nanocrystal-polymer interface. Thus, this swelling-induced heterogeneity resists the reassociation of the sacrificed β-cyclodextrin/adamantane complexes. Furthermore, the unstable nanocrystal-polymer interface induces the crack propagate along the nanocrosslinker surface, which remarkably retards the crack propagation during the stretch.

Keywords: cellulose nanocrystals; composite hydrogels; heterogeneous structures; host-guest interactions; nanoparticle-polymer interface.