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

Abstract

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.

Microcrystalline Cellulose Surface-Modified with Acrylamide for Reinforcement of Hydrogels

“…Further increasing the AM-MCC content would lead to obvious aggregation of the particles, which is indicated in Figure . However, the aggregation of the AM-MCC particles has not formed rigid frameworks, which have been reported to drastically improve the strength of hydrogels. ,,,,,− Instead, the aggregation of the AM-MCC particles in the present work would have destroyed the uniform microstructures of the composite hydrogels, resulting in a reduction of the mechanical properties. The above results clearly evidence the reinforcement of the PDMAA hydrogel by a proper amount of AM-MCC particles.…”

“…Meanwhile, the peak for  OH and NH groups shifted to 3466 cm −1 for the composite hydrogel, which generally implies strong interactions between the components. 22,32,33 This means that new intermolecular hydrogen bonding between the AM-MCC and the PDMAA chains might have been formed.…”

Multi‐Responsive Bilayer Hydrogel Actuators with Programmable and Precisely Tunable Motions

“…The flourishing development of versatile stimuli‐responsive polymers leads to the emergence of flexible polymer actuators . Hydrogels are highly hydrated 3D polymer networks, which showed excellent biodegradability, biocompatibility, and permeability . In recent years, hydrogel‐based actuators that can undergo precisely tunable motions enable transformative applications in diverse areas, such as biomedical fields, soft robotics, and soft electronics .…”

Glycogen as a Cross-Linking Agent of Collagen and Nanohydroxyapatite To Form Hydrogels for bMSC Differentiation

“…The modified glycogen CHO-Gly-guanido was mixed with collagen and nano-HAP in turn followed by covering with carbonate buffer for 12 h to form C/G/H composite hydrogels at 37 °C. The binding between these components was mainly dependent on the Schiff base, which forms a dynamic bond between glycogen and collagen, as well as the electric charge between glycogen and nano-HAP (Figure A). ,, To fully study the properties of C/G/H hydrogels, a series of hydrogels with different compositions were prepared. First, considering the effect of component concentration on physical properties and cell behavior, we increased the amount of collagen and CHO-Gly-guanido gradually but kept setting the molar ratio of −NH 2 /–CHO to 1:4 to maximize the reaction degree.…”