Designing End‐of‐Life Recyclable Polymers via Diels–Alder Chemistry: A Review on the Kinetics of Reversible Reactions

The purpose of this review is to critically assess the kinetic behavior of the furan/maleimide Diels-Alder click reaction. The popularity of this reaction is evident and still continues to grow, which is likely attributed to its reversibility at temperatures above 100 °C, and due to its biobased "roots" in terms of raw materials. This chemistry is used to form thermoreversible crosslinks in polymer networks, and thus allows the polymer field to design strong, but also end-of-life recyclable thermosets and rubbers. In this context, the rate at which the forward reaction (Diels-Alder for crosslinking) and its reverse (retro Diels-Alder for decrosslinking) proceed as a function of temperature is of crucial importance in assessing the feasibility of the design in real-life products. Differences in kinetics based from various studies are not well understood, but are potentially caused by chemical side groups, mass transfer limitations, and the analysis methods being employed. In this work, all the relevant studies are attempted to be placed in perspective with respect to each other, and thereby offer a general guide is offered on how to assess their recycling kinetics.