Closed-Loop Recyclable, Self-Catalytic Transesterification Vitrimer Coatings with Superior Adhesive Strength, Fire Retardancy, and Environmental Stability

The nondegradability, nonreusability, and flammability of epoxy coatings have brought serious environmental and safety issues. Herein, a multifunctional, fire-retardant epoxy vitrimer coating (DCNC/45PETO) was prepared via curing bis(2,3-epoxypropyl)cyclohex-4-ene-1,2-dicarboxylate (DCNC) with a well-designed phosphaphenanthrene-containing polyethylenimine (PETO) at room temperature. DCNC/45PETO exhibits excellent adhesion to different substrates, with a high adhesive strength of 7.9 MPa on wood, outperforming previous wood coatings/adhesives. The DCNC/45PETO coating endows wood with excellent fire retardancy, including a high limiting oxygen index of 34.0% and a vertical burning (UL-94) V-0 rating. DCNC/45PETO demonstrates durable adhesion and fire-retardant performances in harsh environments. The self-catalytic transesterification within the DCNC/45PETO network effectively avoids the application of extra toxic catalysts, and this coating can be reused for at least 5 times in mild conditions without compromising its performances. This study provides an innovative design strategy for creating multifunctional vitrimer coatings, showing great application potential in the construction field.