Mechanically Strong, Thermally Healable, and Recyclable Epoxy Vitrimers Enabled by ZnAl-Layer Double Hydroxides

To meet the demand of sustainable development, epoxy vitrimers based on the dynamic transesterification reaction (DTER) have received considerable attention recently due to their reprocessability and repairability. However, they suffer from low mechanical strength and rely heavily on external catalysts to ensure their curing and repair. Herein, we report a facile design of a novel ZnAl-LDH-catalyzed epoxy vitrimer nanocomposite via introducing ZnAl-layered double metal hydroxide (ZnAl-LDH) nanosheets. Our results show that ZnAl-LDH can be well dispersed in the epoxy vitrimer. Notably, ZnAl-LDH has multifunctionality, which can simultaneously catalyze the curing reaction and enhance the mechanical strength and repairable efficiency of the resultant vitrimer. For instance, the peak curing temperature of epoxy vitrimer with 2 wt % ZnAl-LDH is 8 °C lower than that of an epoxy vitrimer under the same loading between Zn2+ of Zn(OAc)2, demonstrating a strong catalytic action. The tensile strength and Young's modulus of ZnAl-LDH/epoxy resin (ER) increase from 18 and 156 MPa to 42 and 307 MPa, respectively, due to the reinforcing effect of ZnAl-LDH and the increased cross-linking density. The repairable efficiency of ZnAl-LDH/ER can reach 95% after repair at 200 °C for 1 h, which is mainly due to the abundant catalytic sites and large contact areas of the ZnAl-LDH lamella. Hence, this work offers an innovative and scalable strategy for creating epoxy vitrimers combining exceptional mechanical strength and high repairable efficiency, which holds great promise for many practical applications in the industry.