Selective Laser Sintering 4D Printing of Dynamic Cross-linked Polyurethane Containing Diels-Alder Bonds

Selective laser sintering (SLS) four-dimensional (4D) printing of smart materials remains a big challenge and largely unexplored due to the lack of suitable materials. Here, we developed one kind of polyurethane containing reversible Diels-Alder bond (PUDA) covalent adaptable network (CAN) with self-healing and shape memory functions for SLS 4D printing. The dynamic mechanism of the Diels-Alder bonds was confirmed by H-1 NMR and in situ FTIR Furthermore, the kg-scale PUDA materials as well as their carbon nanotube (CNT) composite powders were prepared by the freeze-grinding method. The SLS printed PUDA materials show nearly isotropic mechanical properties due to the improved interlayer interaction by dynamic cross-linking. The SLS printed PUDA/CNT composites possess NIR-triggered self-healing and shape memory functions. This study provides a paradigm for designing dynamic polymers/ composites for SLS 4D printing.