Diels–Alder Polymers

AbstractThe Diels–Alder (DA) cycloaddition is extensively used in polymer chemistry. Linear, network, and hyperbranched polymers have been prepared from monomers and prepolymers containing a diene and a dienophile. Because of the simple reaction conditions, high yield, and high selectivity, the DA reaction has recently been rerecognized as a member of the click‐chemistry family. Polymers with unique architectures (e.g., block and graft copolymers, star polymers, telechelic polymers, dendrimers, and dendronized polymers) have been prepared based on this concept. Many DA reactions are thermally reversible. Enthalpically favorable forward cycloaddition reaction proceeds at low temperature, whereas the opposite cycloreversion proceeds at moderate‐to‐high temperature. Among the various options for optimizing DA reactions in polymer synthesis, researchers have focused on the diene–dienophile combination. Ease of reactant preparation, reaction rate of the DA cycloaddition, equilibrium constant of the DA reaction at room temperature, and temperature above which the retro‐DA reaction proceeds are key points in choosing this option. In addition, reversibility has been exploited in developing various functional polymers such as recyclable gels and thermosets, shape‐memory polymers, and crack‐healing polymers. This article surveys DA reactions in polymer synthesis and coupling, including the click‐chemistry approach, and functionality of DA polymers mainly based on the reversibility.