A Self‐Healing System for Polydicyclopentadiene Thermosets

Abstract Self‐healing offers promise for addressing structural failures, increasing lifespan, and improving durability in polymeric materials. Implementing self‐healing in thermoset polymers faces significant manufacturing challenges, especially due to the elevated temperature requirements of thermoset processing. To introduce self‐healing into structural thermosets, the self‐healing system must be thermally stable and compatible with the thermoset chemistry. This article demonstrates a self‐healing microcapsule‐based system stable to frontal polymerization (FP), a rapid and energy‐efficient manufacturing process with a self‐propagating exothermic reaction (≈200 °C). A thermally latent Grubbs‐type complex bearing two N ‐heterocyclic carbene ligands addresses limitations in conventional G2‐based self‐healing approaches. Under FP's elevated temperatures, the catalyst remains dormant until activated by a Cu(I) co‐reagent, ensuring efficient polymerization of the dicyclopentadiene (DCPD) upon damage to the polyDCPD matrix. The two‐part microcapsule system consists of one capsule containing the thermally latent Grubbs‐type catalyst dissolved in the solvent, and another capsule containing a Cu(I) coagent blended with liquid DCPD monomer. Using the same chemistry for both matrix fabrication and healing results in strong interfaces as demonstrated by lap‐shear tests. In an optimized system, the self‐healing system restores the mechanical properties of the tough polyDCPD thermoset. Self‐healing efficiencies greater than 90% via tapered double cantilever beam tests are observed.