The role of dynamic covalent bonds on mechanical properties of rubber vitrimer with hybrid networks

Rubber is widely applied due to its high elasticity and durability, but traditional crosslinked networks are non-recyclable. The incorporation of dynamic covalent bonds endows vitrimers with recyclability and self-healing ability. However, the regulatory effect of curing kinetics and chemical ratio on dynamic covalent bonds has not been systematically studied, and such regulation is crucial for designing high-performance rubber vitrimers. In this work, rubber vitrimers with hybrid network were synthesized by using epoxy monomers and curing agent containing disulfide bonds. By varying the chemical ratio of soft segments (PEG) and hard segments (BPDG or DGEBA), and tuning curing time, we characterized their dynamic performance, tensile properties and fracture toughness. Furthermore, kinetic equation was incorporated into and used to extend the Lake–Thomas model, enabling quantitative description and prediction of fracture energy. The results demonstrate that increased curing degree and disulfide bond proportion enhance the fracture toughness and fracture strain of the rubber polymer, but slightly reduce its strength and modulus. Moreover, the introduction of dynamic covalent bonds favors both fracture toughness and dynamic performance. This work provides theoretical guidance and processing strategies for the design of high-performance rubbers.