Self-Healing and shape memory reconfigurable Poly(urethane-urea-amide) elastomers containing multiple dynamic bonds for improving performance of 4D printout

As smart polymer material, 4D printed shape memory polymers (SMPs) can fix a temporary shape under a certain external stimulus and recover to the permanent shape under the same type of stimulus, which has attracted tremendous attention because of its potential applications in flexible electronics, biomedicine and other emerging fields. However, the traditional 4D printable polymer products in the practical multifunctional application usually have poor self-healing, shape memory, recyclability. Herein, a series of poly(urethane-urea-amide) elastomers (sPUUA) containing thiocarbamate, disulfide and carbamate dynamic bonds are successfully prepared by the copolymerization of isocyanate-terminated polyurethane prepolymer (OPU), polyetheramine and amino-terminated oligomeric polyamide-1212 (PA1212) in twin-screw extruder via reactive extrusion. Notably, sPUUA elastomers have self-healing, one-way/two-way and multiple shape memory functions. Damaged sPUUA-TU3 and sPUUA-TU3-H10 films with 0.9 wt% DBTDL can be healed by thermal treatment at 150 °C for 30 min and they also exhibit excellent micro-scratch elimination ability. Furthermore, sPUUA-TU3-H10 demonstrates a tensile stress of 9.6 MPa and an elongation at break of 402.3 % with a healing efficiency of 69 %, and exhibits the outstanding shape memory behavior based on supramolecular interactions and dynamic covalent bonds. Then the sPUUA elastomers were granulated, dried, extruded by single screw extruder, and then hot-stretched by pulling rollers into 1.75 ± 0.05 mm diameter wires for FDM 4D printing. The self-healing, macroscopic shape memory and reconfigurability of the as-printed objects were also demonstrated. Accordingly, sPUUA elastomers based on 4D printing will enable vast potential applications in the fields of multifunctional shape shifting devices, biomedicine, robotics and additive manufacturing.