Thermal-driven H-bond reconfiguration for bioinspired high-strength anisotropic supramolecular hydrogels

Natural anisotropic tissues, such as tendons and cartilage, achieve remarkable mechanical properties and various biofunctions through oriented hierarchical structures. Inspired by organisms, we developed a synergistic molecular and structural engineering technique based on thermodynamically reversible reconfiguration of hydrogen bonds to achieve highperformance anisotropic supramolecular hydrogels by quenching pre-stretched polymer networks. Inherent multiple hydrogen bonds gradually dissociate under high-temperature processing to allow the well alignments of polymer chains by uniaxial pre-stretching. The oriented polymer chains are then fixed on-site by rapid quenching-mediated hydrogen bond reconstruction at low temperature (e.g., ice bath). This process merely relies on the inherent hydrogen bonds of polymer chains instead of traditional salting-out, metal ionic coordination and solvent effects. The optimal anisotropic hydrogel shows tensile strength of 19.4 ± 0.7 MPa, and toughness of 53.8 ± 5.2 MJ/m³ along to the pre-stretching direction, which are 2.6 and 1.7 times higher than that of unquenched isotropic hydrogels. This general strategy is applicable to different strong hydrogen bonding supramolecular hydrogel systems. Furthermore, we also fabricate anisotropic hydrogel fibers as damping materials. The general approach to prepare anisotropic supramolecular hydrogels promises great potential for various engineering applications, such as protective and cushioning materials, flexible optical and electronics, and mechanofunctional scaffolds.