Lignin-dynamic networks break the strength-toughness trade-off in thermoplastic elastomers.

Abstract

The long-standing trade-off between strength and toughness has constrained the performance of thermoplastic elastomers. Here, we address this challenge by constructing a three-dimensional supramolecular network in a thermoplastic polyurethane elastomer via dynamic chain extension with lignin polyols. Unlike conventional linear or branched extenders, lignin's rigid aromatic backbone and abundant hydroxyl groups serve as multifunctional nodes that simultaneously enhance microphase separation and establish a hierarchical, dynamic hydrogen-bonding network. At an optimal lignin loading of 10 mol%, the resulting material achieves a tensile strength of 127.7 ± 9.52 MPa and a toughness of 1.43 ± 0.11 GJ m⁻³-representing the highest combination reported for polyurethane elastomers to date. In situ spectroscopy and molecular dynamics simulations reveal that lignin transforms the hydrogen-bond landscape from a static binary system into a dynamic, spatially organized architecture, enabling multi-scale energy dissipation through sacrificial bond rupture and subsequent network reorganization. This lignin-engineered network also imparts superior damage tolerance and high elastic recovery to fiber-reinforced composites. This work unveils a general strategy for employing bio-aromatic motifs to effectively decouple the strength-toughness conflict in thermoplastic elastomers, paving the way for high-performance composites.