The ability to behave in a fluidlike manner fundamentally separates thermoset and thermoplastic polymers. Bridging this divide, covalent adaptable networks (CANs) structurally resemble thermosets with permanent covalent crosslinks but are able to flow in a manner that resembles thermoplastic behavior only when a dynamic chemical reaction is active. As a consequence, the rheological behavior of CANs becomes intrinsically tied to the dynamic reaction kinetics and the stimuli that are used to trigger those, including temperature, light, and chemical stimuli, providing unprecedented control over viscoelastic properties. CANs represent a highly capable material that serves as a powerful tool to improve mechanical properties and processing in a wide variety of polymer applications, including composites, hydrogels, and shape-memory polymers. This review aims to highlight the enabling material properties of CANs and the applied fields where the CAN concept has been embraced.
