Elastic vitrimers: Beyond thermoplastic and thermoset elastomers

Thermoset elastomers are widely used in industry and frontier research due to their advantage of mechanical robustness, high thermal/chemical resistance, and good dimensional stability. However, the presence of permanent crosslinks in thermoset elastomers significantly limits their recyclability. Polymer networks with associative exchangeable crosslinkers, called vitrimers, are reported to provide a path to polymer circularity for traditional thermosets. Herein, we provide a review of representative studies dedicated to the design, synthesis, fundamental physics, and property evaluation of elastic vitrimers that are synthesized based on different types of dynamic covalent bonds. Control on the network parameters (e.g., type of chemical bond, crosslink density, polymer backbone, and network architecture) of the elastic vitrimers enables them to tailor their mechanical performance, network dynamics, self-healing capability, and recyclability. The dynamic nature of reversible chemical bonds allows controlling the responsive behavior of elastic vitrimers to a variety of external stimuli, such as temperature, light, and moisture. Special attention is paid to the critical physical parameters in elastic vitrimers, such as topology freezing temperature (T_v), and their comparison with those of widely used thermoset and thermoplastic elastomers. The merits, bottlenecks, and future research directions of elastic vitrimers are also discussed toward their practical applications in various fields.