NIR-triggered dynamic exchange and intrinsic photothermal-responsive covalent adaptable networks

Fabrication of covalent adaptable networks with the combination of intrinsic photothermal responsiveness, NIR-triggered welding, multiple-shape memory, and selective shape memory recovery remains a challenge. Herein, we developed a series of poly(urea-oxime urethane) thermosets (PUOUs) based on 1,4-benzoquinone dioxime, Jeffamine D230, and hexamethylene diisocyanate trimer using an organic bismuth compound (U600) as the catalyst. The inherently strong photothermal effect of the PUOUs could trigger and manipulate the dynamic exchange of oxime-carbamate bonds to undergo rapid welding by near-infrared laser (NIR, λ = 808 nm) irradiation. The lap shear strength of the two PUOUs with an overlapped area of 4 cm × 4 cm reached 1.2 MPa after irradiation by a NIR laser for 150 s with an irradiation intensity of 2.7 W/cm². Due to the two independent glass transition temperatures of the PUOUs, triple shape memory property was detected and selective shape memory recovery could achieve in the area subjected to NIR irradiation. Hence, the PUOUs show vast potential for the construction of weldable thermosets and may find applications in intelligent shape-memory devices.