Covalent adaptable networks of polydimethylsiloxane elastomer for selective laser sintering 3D printing

Polydimethylsiloxane (PDMS) elastomer is one of most investigated and pioneering 3D printing materials. However, the powder-based 3D printing remains a big challenge due to the thermoset intrinsic character of PDMS. Here we realized the powder-based selective laser sintering (SLS) 3D printing of PDMS elastomer based on one kind of novel self-designed PDMS covalent adaptable networks (CANs) containing hindered pyrazole urea dynamic bonds. The dynamic chemical mechanism of the hindered pyrazole urea bonds is confirmed by small molecule models experiments, density functional theory calculation, and also stress relaxation analysis. The electron-donating large steric hindrance substituent in the pyrazole ring was found to effectively promote the dynamic character of pyrazole urea bond. The PDMS CANs show excellent self-healing and reprocessing properties. Furthermore, kilo-scale PDMS powders were prepared by cryogenic grinding and the powder morphology was optimized for SLS 3D printing. A PDMS insole with complex structure designed based on the personalized foot pressure distribution data was printed, and the foot orthotic and self-healing functions for the insole were demonstrated.