Thermally Reversible Diels–Alder Bond‐Containing Acrylate Networks Showing Improved Lifetime

Photopolymerization of (meth)acrylates into highly crosslinked networks is in general accompanied by volumetric shrinkage, often leading to premature material failure. In this work, thermoreversible Diels–Alder groups are investigated to explore their effect on material lifetime. A difunctional acrylic monomer containing Diels–Alder moieties is synthesized and successfully incorporated in a polymer network by photopolymerization. It is demonstrated that upon heating above 150 °C, the Diels–Alder bonds open, yielding topological rearrangements of the network. The mechanical properties of the material after opening of the Diels–Alder moieties are investigated by tensile testing, showing a high strain‐rate dependence of the yield stress which is indicative of a longer lifetime at the higher strain rates that are prevalent in load‐bearing applications. Photopolymerization using diacrylates containing a Diels–Alder adduct results in networks with thermally reversible cross‐links. Upon thermal treatment of these materials, the retro Diels–Alder reaction causes a reduction in crosslink density, releasing any potentially built‐up shrinkage stresses, which in turn leads to an improved lifetime of the material under load‐bearing conditions.