Soft–Hard Phase Microinfiltration Enables Tunable Hydrogen‐Bond Network in High‐Performance Bio‐Based Polyurethanes

Sustainable bio‐based polyurethanes (PUs) combining high strength, high toughness, fatigue resistance, and stimuli‐responsive properties are highly desirable for flexible electronics, biomedical engineering, and anticounterfeiting applications. However, overcoming the conventional trade‐off between strength and toughness through hydrogen‐bond network engineering remains a formidable challenge. Herein, we report a soft–hard phase microinfiltration strategy by introducing varying amounts of poly(hexamethylene 2,5‐furandicarboxylate) (PHF) into the PUs matrix. The ester groups of PHF gradually infiltrate from the soft–hard interface to the hard domain through competitive interactions with the inherent hydrogen‐bond network. The hydrogen‑bond network restructuring induced by this microinfiltration process enables the BFPU‑10 elastomer to achieve its optimal mechanical performance: a tensile strength of 12.49 ± 0.81 MPa, an elongation at break of 1410 ± 41.74%, and a toughness of 71.83 ± 4.75 MJ m −3 . In addition, spatial confinement imposed by tertiary amine groups and the rigid furan skeleton give the BFPU‐ x elastomers intrinsic blue aggregation‐induced emission and reversible optical responses to temperature and mechanical strain. This research presents a molecular design strategy for restructuring the hydrogen‐bond network in sustainable PUs and provides a new pathway for the development of elastomers with high mechanical robustness and sensitive optical responsiveness.