Light-Assisted Reconfiguration of Thermosetting Polyurethane Enabled by Gradient Plasticity

Shape memory polymers or self-folding materials are able to achieve sophisticated three-dimensional (3D) shape-changings, but the obtained structures are usually temporary shapes. Dynamic covalent chemistry addressed this problem by realizing topological rearrangement of a polymer covalent network in solid state. In this paper, we designed a convenient strategy to achieve 3D shape-changings of thermosetting polyurethane (PU) with the aid of Near Infrared (NIR) light, including temporary and permanent shapes. A temperature gradient emerges in the PU materials upon NIR light, which results in formation of gradient plasticity in the stretched PU bilayers enabled by transcarbamoylation. After removing the external stress, various 3D shapes can be obtained as a result of asymmetrical contraction. The degree of plasticity can be adjusted by the NIR irradiation time and catalyst amounts. Besides, the plasticity region can also be strategically selected to obtain more complex permanent shapes.