High-Performance Epoxy Vitrimers with the Joint Action of Dual Dynamic Covalent Bonds

Abstract

Epoxy vitrimers have attracted increasing research attention owing to their stable physical properties, reprocessability, recyclability, and degradability. Among them, rapid self-healing can be achieved in dual dynamic covalent epoxy vitrimers. However, research on the performance and high-strength surface welding of dual dynamic covalent epoxy vitrimers with flexibility is still insufficient. Herein, we report a dual dynamic covalent epoxy vitrimer cocross-linked by dimer acid (DAA) and 3,3′-dithiodipropionic acid (DTDA), named E51-DAAx-DTDAy. The results suggest that the stress relaxation and self-healing speed of vitrimers is improved and the mechanical properties can be restored by 81.2% after 24 h of healing. Additionally, significant recyclability is found in E51-DAAx-DTDAy, with a maximum recovery rate of 119.4% in tensile strength and 124.8% in elongation at break after three times of recycling. Furthermore, Tv of E51-DAAx-DTDAy was above 140 °C; meanwhile, E51-DAAx-DTDAy had better insulation properties, making them more suitable for use as thermosetting materials at moderate temperatures in electronic equipment. E51-DAAx-DTDAy can be recycled by chemical reagents, and green cycling can be achieved. These are attributed to the contributions of disulfide bonds and hydroxyl ester bonds in the network topology.