Synergistic Hydrogen Bonding Topology Enables Ultra-Robust Recyclable Polyurethane Elastomers for Multifunctional Strain Sensors.

There has long been a trade-off between mechanical strength and toughness in polyurethane (PU) elastomers. This limitation arises from stress concentration and inefficient energy dissipation within the rigid domains. Therefore, a gradient hydrogen bonding topology strategy is proposed that constructs hierarchical crosslinked networks incorporating both strong (urea-based) and weak (ester-based) hydrogen bonds. By precisely controlling these bonds, an optimized polyurethane elastomer (SPU, where 0.5 denotes the crosslinking density parameter) is achieved with a tensile strength of 27.4 MPa-2.5 times higher than that of systems dominated by weak hydrogen bonds-alongside exceptional toughness (188.1 MJ m) and fracture energy (115.8 kJ m). These values surpass those of most previously reported PU elastomers and even exceed the toughness of natural spider silk (100-160 MJ m). The dynamic nature of the weak hydrogen bonds enables rapid self-healing (100% recovery after 24 h at 80 °C) and excellent recyclability (less than 5% performance loss after five cycles), while the strong hydrogen bonds maintain structural integrity. Notably, integrating silver-coated SPU into wearable sensors enables real-time monitoring of limb movements, facial expressions, and voice recognition, providing the way of health monitoring. This work offers insights into designing mechanically adaptive polymers through hierarchical-level engineering.