Nanoporous, Ultrastiff, and Transparent Plastic-like Polymer Hydrogels Enabled by Hydrogen Bonding-Induced Self-Assembly.

Most natural supporting tissues possess both exceptional mechanical strength, a significant amount of water, and the anisotropic structure, as well as nanoscale assembly. These properties are essential for biological processes, but have been challenging to emulate in synthetic materials. In an effort to achieve simultaneous improvement of these trade-off features, a hydrogen bonding-induced self-assembly strategy was introduced to create nanoporous plastic-like polymer hydrogels. Multiple hydrogen bonding-mediated networks and nanoporous orientation structures endow transparent hydrogels with remarkable mechanical robustness. They exhibit Young's modulus of up to 223.7 MPa and a breaking strength of up to 10.3 MPa, which are superior to those of most common polymer hydrogels. The uniform porous nanostructures of hydrogen-bonded hydrogels contribute to a significantly larger specific surface area compared to conventional hydrogels. This allows for the retention of high mechanical properties in environments with a high water content of 70 wt %. A rubbery stage is observed during the heating process, which can reverse and reshape the manufacture of objects with various desired 2D or 3D shapes using techniques such as origami and kirigami. Finally, as a proof-of-concept, the outstanding mechanical properties of poly(MAA--AA--NVCL) hydrogel, combined with its high water content, make it suitable for applications such as smart temperature monitors, multilevel information anticounterfeiting, and artificial muscles.