Vinylogous Urethane Based Epoxy Vitrimers with Closed-Loop and Multiple Recycling Routes

Vitrimers, a new class of covalently cross-linked materials, can be thermally reprocessed and recycled while maintaining network integrity. However, efficient and convenient recycling of vitrimers is still a major challenge. Herein, a facile one-pot method is presented for preparing vinylogous urethane-based epoxy vitrimers with multiple recycling routes. By adjusting network structure through the molar ratio of the chain extender and cross-linker, the cured epoxy vitrimer has high Tg (>75 °C), tensile strength (>70 MPa), and Young's modulus (>1700 MPa) and good solvent resistance. Owing to the incorporation of vinylogous urethane bonds, the epoxy vitrimer is reprocessable and the repeatedly reprocessed samples exhibit nearly unchanged mechanical performances. Moreover, it can achieve a chemical closed-loop recycling with solvent assistance and the resulting vitrimer shows comparable comprehensive performances. Amazingly, the discarded epoxy vitrimer can be completely degraded within 25 min at 30 °C in acid solutions, which will greatly facilitate the tackling of plastic waste at the life end. Therefore, this work provides a rational network design for a combination of high comprehensive performances and multiple recycling routes.