Strong, Reconfigurable, and Recyclable Thermosets Cross-Linked by Polymer-Polymer Dynamic Interaction Based on Commodity Thermoplastics

Polymer networks cross-linked by dynamic covalent bonds possess outstanding mechanical and rheological properties and are expected to be potential alternatives to conventional thermosets. However, while many recent studies of dynamically cross-linked thermosets focused on the employment of small molecular cross-linkers, the macro-cross-linking approach and the corresponding thermosets have been less demonstrated. In this work, reconfigurable and catalyst-free thermosets were synthesized by dynamic polymer-polymer interaction based on reversible boronic ester bond, providing simple and efficient access toward materials with improved mechanical strength and toughness in comparison to related commodity thermoplastics. The dynamic exchange of covalent bonds dispersed between polymer chains enables the materials to be malleable, recyclable, and healable under thermal conditions and readily processable with mechanical mixing without solvent. Moreover, the materials' mechanical and rheological properties could be tuned by changing the cross-linking density. Although the dynamic networks exhibited good resistance against organic solvents, they could be cleaved as triggered by acids or diols and recycled through the de-cross-linking/re-cross-linking pathway. Given the dramatically increasing interest in environmentally sustainable materials, this polymer-polymer interaction mode provides a robust approach to engineering polymers with improved performance compared with the thermoplastic counterparts.