Molecular Steric Engineering Enables High-Strength and Self-Healing Polyurethane Elastomer for Flexible and Sensitive Nanosensors

Acquiring a versatile polyurethane (PU) elastomer with both high mechanical properties and rapid low-temperature healing for flexible nanosensors represents a significant challenge. Inspired by the synergistic effects of dynamic bonds, we introduce the dynamic sextuple hydrogen bonds (H-bonds) from adipic dihydrazide (AD) and flexible dynamic disulfide bonds (S–S bonds) from the chain extender 3,3′-dithiobis(2-butanol) (DS) into PU main chains to fabricate a high-performance elastomer (PU-3) with remarkable mechanical robustness and rapid self-healing capability. Specifically, AD imparts PU-3 with an exceptional tensile strength of 40.5 MPa and a toughness of 287.8 MJ m–3. A 1.1 g sample (50 mm × 10 mm × 1.3 mm) supports loads up to 11,000 times its own weight. In addition, the excellent DS unit, featuring four branched methyl groups with a substantially larger molecular volume, renders the PU-3 more flexible with an outstanding elongation at break of 1445.2%. Moreover, PU-3 exhibits excellent resilience, self-healing efficiency, and recyclability. As a result, a flexible polymer/carbon nanotube composite nanosensor is constructed from this elastomer matrix and multiwalled carboxylated carbon nanotubes (MWCNTs-COOH) as the conductive filler, exhibiting outstanding sensitivity and rapid response and recovery capabilities, thereby highlighting its potential for applications in health monitoring and intelligent wearable electronics.