Multishape Programming of Shape Memory Polymer Assemblies Fabricated by Vat Photopolymerization-Based 3D Printing and Interfacial Welding

The combination of three-dimensional (3D) printing and shape memory polymers (SMP) enables programmable shape morphing of complex 3D structures, which is commonly termed four-dimensional (4D) printing. The process requirements of vat photopolymerization-based 3D printing impose limitations on the molecular structure design of SMPs, making it challenging to achieve triple- or multiple-shaped memory effects. Herein, we printed SMPs with different T_g values and obtained an SMP assembly through interfacial welding. The welding process is facilitated by the dynamic exchange of hindered urethane bonds at the interface. The resulting SMP assembly exhibits a quadruple shape memory effect, enabling programmable sequential deformation. The advantage of this approach is that the molecular design and the corresponding thermodynamic properties of different welding SMP components can be independently adjusted, enabling a greater range of shape and functional variations in the final 3D SMP assembly.