Controlling the Physical Properties in Hybrid Hydrogel Networks via Tunable Supramolecular Interactions

The complex interplay of covalent and noncovalent interactions is intrinsically connected to the formation of biological macromolecules, including proteins and carbohydrates. The design of synthetic materials that exhibit a similar interplay of such complex interactions is challenging. Most synthetic networks use purely covalent polymers in different concentrations to capture the bulk stiffness. Here, we combine covalent and dynamic network interactions in fully synthetic systems. In a systematic approach, permanent covalent cross-links are replaced by dynamic cross-links. Via this approach, network mechanics can be tuned over several orders of magnitude, i.e., from 10 to over 1000 Pa. This large tunability is achieved by changes in the molecular design of the dynamic cross-links, all while the fundamental design and concentration of the components are kept constant. Furthermore, where experiments showed a clear relationship between the design of the dynamic cross-links and the mechanical strength, coarse-grained molecular dynamics simulations showed a similar trend between networks mechanics and cross-link interaction strength. Overall, we show a new approach for the design of networks in which components and concentrations are kept similar, but a wide range of physical properties can be captured by tuning the molecular design of the cross-links. In this way, synthetic materials are brought closer to the design and tunability of biological matter.