Mechanically Ductile, Self-Healable, Low-Temperature, and Water-Tolerant Polyurethane for High-Performance Strain Sensor

The water degradation of polyurethane (PU) elastomers can seriously influence the quality of related equipment and instruments and may even entail serious economic and safety problems as well as environmental hazards. Therefore, the development of PU with water tolerance to ensure its safety and functional stability is of great importance for practical applications. Here, the hydrophobic functional component α-cyclodextrin (α-CD) has been further introduced into the current hydroxyl-terminated polybutadiene (HTPB)-based water-resistant PU molecular chains. Benefiting from the hydrophobic inner cavity in the α-CD structure, on the one hand, the water resistance of PU elastomers was significantly improved, while on the other hand, the mechanical properties of the PU molecular chains were enhanced thanks to the covalent cross-linked network in the structure. The PU elastomer exhibited a high tensile strain of 1307%, fracture energy of 52,800 J m^–2, puncture energy of 374 mJ, and self-healing efficiency of 98% when heated for 2 h. Remarkably, the as-prepared PU elastomer, strain sensor, and conductive inks still exhibited excellent mechanical properties, stability, sensing performance, and conductivity even in harsh underwater and low-temperature environments. Moreover, the strain sensor possessed excellent recyclability and reprocessability, which further extended the practical applications of the strain sensor in harsh environments.