Multiple H‐Bonding Chain Extender‐Based Ultrastiff Thermoplastic Polyurethanes with Autonomous Self‐Healability, Solvent‐Free Adhesiveness, and AIE Fluorescence

Abstract Developing an autonomous room temperature self‐healing supramolecular polyurethane (PU) with toughness and stiffness remains a great challenge. Herein, a novel concept that utilizes a T‐shaped chain extender with double amide hydrogen bonds in a side chain to extend PU prepolymers to construct highly stiff and tough supramolecular PU with integrated functions is reported. Mobile side‐chain H‐bonds afford a large flexibility to modulate the stiffness of the PUs ranging from highly stiff and tough elastomer (105.87 MPa Young's modulus, 27 kJ m −2 tearing energy), to solvent‐free hot‐melt adhesive, and coating. The dynamic side‐chain multiple H‐bonds afford an autonomous self‐healability at room temperature (25 ° C). Due to the rapid reconstruction of hydrogen bonds, this PU adhesive demonstrates a high adhesion strength, fast curing, reusability, long‐term adhesion, and excellent low‐temperature resistance. Intriguingly, the PU emits intrinsic blue fluorescence presumably owing to the aggregation‐induced emission of tertiary amine domains induced by side‐chain H‐bonds. The PU is explored as a counterfeit ink coated on the predesigned pattern, which is visible‐light invisible and UV‐light visible. This work represents a universal and facile approach to fabricate supertough supramolecular PU with tailorable functions by chain extension of PU prepolymers with multiple H‐bonding chain extenders.