Multiple responsive self-healing behavior of amino-functionalized CuS-modified thermo-reversible polyurethane containing double dynamic covalent bonds

Abstract

A self-healing polyurethane with five-fold response to thermal, near-infrared light, microwave, sunlight and UV light is prepared by introducing amino-functionalized copper sulfide (CuS-NH₂) nanoparticles into thermally reversible polyurethane containing both Diels-Alder and disulfide bonds. The prepared polyurethane exhibits optimal comprehensive mechanical properties and self-healing performance when the addition amount of CuS-NH₂ is 0.3 wt%. The polyurethane with quite high tensile strength (14.3 MPa), hardness (75 HA), elongation at break (625 %), and toughness (24.85 MJ/m³) can be obtained. Cracks in the modified polyurethane can be self-healed repeatedly through heat-treated at 120 °C for 6 min, or irradiated with 4 W/m² of near infrared light at a wavelength of 808 nm for 60 s, or treated under a 250 W microwave for 80 s, and followed by a heat treatment for 12 h at 60 °C. More importantly, the damaged sample can also be repaired multiply after being treated to simulated sunlight or irradiated with 250–380 nm UV light for 6 h. Results show that the quickest self-healing speed and highest repair efficiency can be resulted when the materials are exposed to near-infrared light. The self-healing behavior is achieved through the cooperation of thermo-reversible Diels-Alder reaction, disulfide bonds exchange, dissociation and regeneration of hydrogen bonds, directional migration of CuS-NH₂ nanoparticles. These findings give important implication for the development of multi-responsive self-healing materials with efficient self-healing capability. Meanwhile, it provides various ideal selections for damage repair under different environments.