Self-Healing, Recyclable, and Solvent Resistant Poly(aryl ether nitrile) Triple Shape Memory Thermosets Cross-Linked with Dynamic Boroxines

Shape memory polymers, which possess exceptional mechanical properties, ease of processing, facile recycling capabilities, and excellent self-healing properties, are critically needed in fields such as smart actuators, biomedicine, electronic devices, and aerospace; yet they remain a challenging research topic. In this study, we propose an innovative approach to overcome these challenges by incorporating soft segments/activation switching monomers and boroxines into poly(aryl ether nitrile) (PEN). The resulting PEN-PEG-B3O exhibits high recovery (95%) and high immobilization (97%) while enabling triple shape memory functionality. Furthermore, the rigid structure of PEN contributes significantly to the material's strength, with a tensile strength of 51.6 MPa anhibits high recovery (95%) and high immobilization (97%) while enabling triple shape memory functionality. Furthermore, the rigid structure of PEN contributes significantly to the material's strength, with a tensile strength of 51.6 MPa and the Young's modulus of 681.7 MPa. Owing to the dynamic nature of the boroxine linkages, PEN-PEG-B3O3 thermosets can be processed in various shapes and can be conveniently reprocessed using a mixed solvent of DMF and ethanol (DMF/EtOH = 8/2, v/v) while maintaining their original mechanical strength. Additionally, these thermosets demonstrate remarkable stability against solvents; they maintain their performance after being immersed in acidic, alkaline, and saline solutions for 90 days.