Multiresponsive and Mechanically Robust Self-Healing Waterborne Polyurethane with Photoluminescent and Acid–Base Adaptive Properties

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This study developed a novel photoluminescent waterborne polyurethane (WPU) elastomer with [2,2′-bipyridine]-4,4′-dicarbohydrazide (BD). The material is characterized by intramolecular rotatable conjugated structures and abundant hydrogen bonding sites, endowing it with excellent mechanical properties, optical responsiveness, and environmental adaptability. [2,2′-bipyridine]-4,4′-dicarbohydrazide-based waterborne polyurethane (WPU-BD) exhibits a high tensile strength of 72.6 MPa and an excellent stretchability at break of 1249.7%, demonstrating remarkable flexibility and durability. Under 260–400 nm ultraviolet (UV) excitation, the material exhibited stable photoluminescence (PL), and the mechanical, thermal, acid–base, and poor solvent experiments revealed that the material realizes fluorescence through a synergistic between aggregation-induced emission and proton-coupled energy transfer. WPU-BD exhibited reversible responses to mechanical stretching and acidic or alkaline environments. These stimuli induced temporary reductions in fluorescence intensity due to molecular chain rearrangements, but the luminescence recovered upon removal of the stimulus, exhibiting reversible PL behavior. Furthermore, the presence of dynamic hydrogen and ionic bonds enabled 100% self-healing efficiency within 24 h at 40 °C, significantly enhancing the lifespan of the material.