Toward 4D Printing of Shape Memory Polymers Based on Polyaryletherketone/NVP/PEGDA through Molecular Engineering and Direct Ink Writing 3D Printing

Abstract

Polyaryletherketone (PAEK), an engineering plastic with exceptional mechanical properties and a high glass transition temperature, can be tailored with various properties to meet the multiple requirements of aerospace applications. However, it remains a challenge to 3D print PAEK with good properties. Herein, a direct ink writing (DIW) 3D printable PAEK ink has been developed, and the yielded PAEK parts possess high tensile strength and excellent shape memory properties. The incorporation of N-vinyl-2-pyrrolidone (NVP) and polyethylene glycol diacrylate PEGDA into PAEK oligomers (PAEKOs) facilitated their versatility as diluents or reactive functional monomers. This characteristic enabled random cross-linking through photoinitiator exposure for the formation of block copolymers, establishing the essential stationary and reversible phases needed for shape memory capabilities. The photocured PAEK demonstrated excellent comprehension performances, including an outstanding tensile strength (42.6 MPa), thermal stability (T d -246 °C), shape fixation ratio (>93%), and shape recovery ratio (>100%). Furthermore, PAEK with a greater shape memory effect was utilized as an actuator to realize gripping and releasing at high temperatures (140 °C). This study therefore provides an emerging strategy to fabricate shape memory components for challenging environments using DIW technology. This approach also holds promise for implementation in systems beyond PAEK which have typically been difficult to print.

Free-Form Liquid Crystal Elastomers via Embedded 4D Printing

“…Another promising method for printing structurally complex 3D architectures is via embedded printing where materials that are not self-supporting are extruded into a liquid or gel matrix. , Embedded printing is a method pioneered in biomedical science for the fabrication of cell-based organisms and organ scaffolds. − Embedded printing of smart, shape-changing materials, here termed embedded 4D printing, has seen limited investigation in the literature. To date, embedded 4D printing has been used to fabricate structures which can change their shape using shape memory polymers (SMP) , and simple, bilayer hydrogels. , Nonetheless, SMPs can only achieve one-way shape transformation before requiring reprogramming while hydrogel-based actuation is slow, requiring up to multiple days for large structures . Some researchers have extruded LCE into the liquid matrix to reduce die-swell during extrusion for high-fidelity printed lines or to provide a catalyst for immediate curing of the LCE ink .…”