Solution-Processable and Thermostable Super-Strong Poly(aryl ether ketone) Supramolecular Thermosets Cross-Linked with Dynamic Boroxines

High-performance engineering polymers (HPEPs) are mechanically robust but difficult to be processed and recycled. Aiming to solve such a problem, herein, supramolecular thermosets with high mechanical strength comparable to HPEPs are fabricated by dynamically cross-linking low-molecular-weight poly(aryl ether ketone)s (PAEKs) with boroxines (denoted as PAEK-B3O3). The PAEK-B3O3 supramolecular thermosets are solution-processable, thermally stable, and recyclable. By tailoring the molecular weight (M-n) of PAEK, the PAEK-B3O3 thermosets can exhibit a tensile strength from approximate to 60.5 to approximate to 97.8 MPa and Young's modulus from approximate to 1.59 to approximate to 4.10 GPa. The mechanically strongest PAEK-B3O3 thermosets, which are derived from PAEK with an M-n of approximate to 9400, have a tensile strength of approximate to 97.8 MPa, Young's modulus of approximate to 1.93 GPa, and glass transition temperature (T-g) of approximate to 154.0 degrees C. Such PAEK-B3O3 thermosets retain a substantial amount of boroxine cross-linkers when the temperature is close to T-g, which guarantees their high mechanical strength at high temperatures. The PAEK-B3O3 thermosets can be solution-processed to products of different shapes and further strengthened by the introduction of polyhedral oligomeric silsesquioxanes modified with phenylboronic acids. Due to the high reversibility of boroxines, the PAEK-B3O3 thermosets can be conveniently re-processed and recycled in the presence of dioxane/ethanol mixture solvent to regain their original mechanical strength.