Bioinspired Fast Room-Temperature Self-Healing, Robust, Adhesive, and AIE Fluorescent Waterborne Polyurethane via Hierarchical Hydrogen Bonds and Use as a Strain Sensor

Developing a new generation of ecofriendly water-based polymeric materials that integrate mechanical robustness, fast room-temperature self-healing, adhesive, and fluorescence remains a formidable challenge. Herein, inspired by titin protein, a series of novel waterborne polyurethanes (WPU-CHZ-NAGA) containing irregular 6-fold and diamide hydrogen bonds are synthesized by introducing carbohydrazide (CHZ) and N,N-bis(2-hydroxyethyl)-3-amino propionyl glycinamide (HO-NAGA-OH) groups. The representative WPU-CHZ₂-NAGA₃ exhibits outstanding mechanical properties (tensile strength of 36.58 MPa, tearing energy of 81.2 kJ m^-2, and toughness of 125.82 MJ m^-3) and fast room-temperature self-healing ability with the aid of ethanol (≥90% within 8 h) originated from hierarchical hydrogen bonds. These properties are superior to those of most of the reported room-temperature self-healing polymer materials. Benefiting from plentiful hydrogen bonds, the WPU matrix achieves excellent adhesive properties without heating or adding curing agents. Interestingly, WPU-CHZ₂-NAGA₃ film emits inherent blue fluorescence due to the aggregation-induced emission effect of tertiary amine groups, and its potential applications in information encryption and anticounterfeiting are further demonstrated. Specially, a eutectic gel strain sensor is also fabricated with WPU-CHZ₂-NAGA₃ and deep eutectic solvent by a simple physical blending method, which can be used to monitor the movement of human fingers and wrists as well as the change in body temperature. In summary, this work provides new insight into the design and synthesis of multifunctional WPU with fast room-temperature self-healing and high mechanical properties.