Unlocking Dual Recycling in Photo-Curable Polycyanurate Thermosets Derived from Bio-Resources

Polycyanurate thermosets are extensively utilized in high-performance applications due to their exceptional thermal and mechanical properties. However, their inherently crosslinked nature has traditionally rendered them nonrecyclable, limiting their sustainability. Recent studies have demonstrated that these networks can undergo dynamic rearrangement under specific conditions, enabling reversibility. In this study, a bio-derived cyanurate monomer from eugenol was synthesized and polymerized via thiol-ene photopolymerization, yielding recyclable polycyanurate thermosets with robust material properties. The dynamic character of these networks was leveraged through nucleophilic aromatic substitution (S_NAr) chemistry, unlocking two distinct recycling pathways: i) selective monomer recovery and ii) closed-loop polymer regeneration. Depolymerization in the presence of eugenol enabled the selective recovery of well-defined monomeric components, while phenol-mediated cleavage facilitated polymer breakdown into chemically recyclable intermediates, which were directly reassembled into reformed thermosets. Both recycling pathways resulted in regenerated polymers that retained their original thermal, mechanical, and thermomechanical properties, demonstrating the efficiency and robustness of this approach. By establishing a controlled depolymerization and reassembly framework, this study introduces a sustainable design strategy for achieving closed-loop recycling in high-performance thermosets, providing a scalable pathway toward circular polymer materials.