Stiff, Tough, and Recyclable Self‐Reinforced Polyurethane Plastics Based on Multiple Hydrogen Bonds Self‐Assembly

ABSTRACT Polyurethanes have garnered significant interest for their tunable functionality, yet molecular‐level designs that simultaneously achieve high stiffness, toughness, and recyclability remain a critical challenge. Herein, we report a self‐reinforcement strategy that leverages dynamic multiple hydrogen bonds (MHBs) to fabricate high‐performance polyurethane materials integrating these properties. By incorporating hydrazine‐linked diurea motifs, a self‐reinforcing effect is realized via MHB‐driven self‐assembly. The resulting material exhibits an outstanding comprehensive mechanical performance, including a hardness of 87 Shore D, a tensile strength of 70 MPa, a Young's modulus of 1.6 GPa, a fracture toughness >100 MJ m −3 , a flexural strength of 52 MPa, and a flexural modulus of 1.2 GPa, outperforming most commercial and reported counterparts. The dynamic, reversible MHBs enable rapid thermal self‐healing and closed‐loop solution reprocessing without property degradation. Spectroscopic and microscopic analyses corroborate the critical role of the reversible MHBs and the resulting self‐assembled nanostructure, which induced distinct microphase separation with rigid domains serving as intrinsic nanofillers. This work establishes a versatile molecular engineering approach for creating sustainable polymers that harmonize superior mechanical performance, self‐healing, and full recyclability, paving the way for next‐generation advanced materials.