Dually Heterogeneous Hydrogels via Dynamic and Supramolecular Cross-Links Tuning Discontinuous Spatial Ruptures

Biological tissues are often highly and multiply heterogeneous in both structure and composition, but the integrity of multiheterogeneity in artificial materials is still a big challenge. Herein, dually heterogeneous hydrogels were constructed with two distinct strategies via dynamic bonds and supramolecular cross-links. The hydrogels showed discontinuous spatial ruptures, and the mechanical behaviors of hydrogels could be tuned. The primary heterogeneity resulted from a nonuniform distribution of dynamic and/or static cross-links. The presence of only primary heterogeneity within hydrogels led to uneven mechanical properties that were represented by discontinuous spatial ruptures during the stretching the hydrogel and therefore caused the necking deformation. Further introduction of the secondary heterogeneity by incorporating anisotropic cellulose nanocrystals (CNC) into the hydrogels allowed the adjustment of the necking phenomenon. Moreover, distinct CNC with diverse surface functionalities exhibited different effects: the “active” CNC with surface-attached dynamic bonds retarded the necking propagation, while the “neutral” CNC without further surface modification promoted the extension of necking points. Thus, the regulation of deformation and fracture mode of hydrogels was achieved by the synergy of dually heterogeneous structure