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

Abstract

Natural anisotropic tissues, such as tendons and cartilages, achieve remarkable mechanical properties and various biofunctions through oriented hierarchical structures. Inspired from organisms, we develop a synergistic molecular and structural engineering technique based on the thermodynamically reversible reconfiguration of hydrogen bonds to achieve high-performance anisotropic supramolecular hydrogels by quenching pre-stretched polymer networks. Multiple inherent hydrogen bonds gradually dissociate under high-temperature processing to allow the good alignment of the polymer chains by uniaxial pre-stretching. The oriented polymer chains are then fixed on-site by rapid quenching-mediated hydrogen bond reconstruction at low temperatures (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 a tensile strength of 19.4 ± 0.7 MPa and toughness of 53.8 ± 5.2 MJ m⁻³ along the pre-stretching direction, which are 2.6- and 1.7-times higher than that of the unquenched isotropic hydrogels, respectively. This general strategy is applicable to different strong hydrogen bonding supramolecular hydrogel systems. Furthermore, we fabricate anisotropic hydrogel fibers as damping materials. This general approach for the preparation of anisotropic supramolecular hydrogels shows great potential for various engineering applications, such as in the fabrication protective and cushioning materials, flexible optoelectronics, and mechano-functional scaffolds.