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

Abstract 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‐B 3 O 3 ). The PAEK‐B 3 O 3 supramolecular thermosets are solution‐processable, thermally stable, and recyclable. By tailoring the molecular weight ( M n ) of PAEK, the PAEK‐B 3 O 3 thermosets can exhibit a tensile strength from ≈60.5 to ≈97.8 MPa and Young's modulus from ≈1.59 to ≈4.10 GPa. The mechanically strongest PAEK‐B 3 O 3 thermosets, which are derived from PAEK with an M n of ≈9400, have a tensile strength of ≈97.8 MPa, Young's modulus of ≈1.93 GPa, and glass transition temperature ( T g ) of ≈154.0 °C. Such PAEK‐B 3 O 3 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‐B 3 O 3 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‐B 3 O 3 thermosets can be conveniently re‐processed and recycled in the presence of dioxane/ethanol mixture solvent to regain their original mechanical strength.