High-Strength, Tough, Furan-Based Polyurethane Elastomers Achieving Performance and Functionality Upgrades through Postdynamic Cross-Linking

Thermoplastic polyurethane elastomers (TPUs) strengthened by hydrogen-bonding interactions offer highly tunable structures and excellent mechanics, yet their properties are typically difficult to further enhance after molding. In this work, a high-strength and ultratough TPU was designed through a postdynamic cross-linking strategy for achieving its performance and functionality upgrades. A small molecule bearing multiple hydrogen-bonding sites and post-cross-linkable reactivity, namely furan-2,5-dicarbohydrazide (FDCH), was first synthesized, and then incorporated into the polyurethane’s backbone to obtain linear furan-based polyurethane elastomers (FPUs) with a high density of hydrogen bonds. The devised FPUs have high strength and toughness with their tensile strength and elongation at break up to 69.4 MPa and 1094%. Leveraging the activated sites (conjugated double bonds) in FDCH as post-cross-linking anchors, cross-linked furan-based polyurethanes (CFPU-3) featuring a dual cross-linked network of hydrogen bonds and dynamic covalent bonds were constructed through a Diels–Alder addition with maleimide derivatives under mild conditions. Capitalizing on the excellent mechanical performance and recyclability of CFPU-3, blending with lithium bis (trifluoromethanesulfonyl) imide can further yield solvent-free ion-conductive elastomers (CFPU-3Li-x%). These CFPU-3Li-x% not only exhibit robust mechanical properties but also deliver reliable strain and temperature sensing, offering a new guideline and theoretical foundation for their application in flexible electronic materials.