Effective autonomous repair of structural thermosets (such as polydicyclopentadiene, pDCPD) requires new self-healing chemistries that recover properties of a damaged material with sufficient interfacial strengths between the matrix and healed layers. Moreover, the self-healing strategy must maintain efficiency over the entire lifespan of the host material. We have previously employed an encapsulation method to heal epoxies with microcapsules containing the second-generation Grubbs catalyst (G2) and DCPD monomer. Adaptation to pDCPD matrix materials prepared by frontal polymerization, however, requires latent catalysts that survive the high temperatures (~200°C) attained during the reaction. Specifically, premature capsule rupture and catalyst degradation are particularly problematic with second-generation Grubbs catalyst (G2). To mitigate these challenges, we employed a thermally latent bis-N-heterocyclic Ru carbene complex and Cu(I) salts as healing agents within a dual-microcapsule system. Prior to damage, the catalyst and initiator are physically isolated. Upon damage of the matrix, the core contents mix and polymerization is initiated within the crack plane. In this system, healing efficiencies of over 80% with a peak load of over 200N are achieved in tapered double cantilever beam testing. Moreover, the microcapsules are stable during frontal polymerization and exhibit shelf-lives of at least 3 months at ambient temperatures.

Self-healing polydicyclopentadiene prepared via frontal polymerization

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