A universal and simple rectangular-topology strategy enables robust hydrogels

The development of high-strength, tough hydrogels is of profound importance for applications ranging from biomedicine to soft robotics. However, a longstanding challenge persists: reconciling mechanical robustness with essential attributes like transparency and biocompatibility. This dilemma stems from the fundamental absence of a structural motif capable of simultaneously supporting high load-bearing capacity, large extensibility, and high-water content. In this study, a novel strategy based on a rectangular topological motif is proposed. This architecture enables a high elastic modulus through a high density of intermolecular hydrogen bonds while maintaining large network mesh sizes. Meanwhile, the fracture strain and strength are significantly enhanced via a strain-induced hardening mechanism, leading to a simultaneous and remarkable improvement in both strength and toughness in single-network hydrogels. The rectangular topological network is constructed through stoichiometric crosslinking of equal amounts of long and short polymer chains. The successful fabrication of high-strength-toughness hydrogels using two different crosslinkers demonstrates the general applicability of the proposed strategy. FT-IR, NMR, and XRD confirmed the formation of the PEG-based rectangular single-network hydrogel with a Young’s modulus of 21.97 MPa, a toughness of 31.04 MJ/m³, and a tensile strength of 7.72 MPa. These values represent the highest mechanical performance reported to date for single-network hydrogels. This novel rectangular topological design strategy is facile and versatile, offering valuable guidance for the development of high-strength-toughness hydrogel materials.