Catalyst morphology and dissolution kinetics of self-healing polymers

The role of the crystal morphology and dissolution kinetics of Grubbs' catalyst on self-healing capability is examined. Self-healing polymers require complete coverage of the crack plane with polymerized healing agent for optimal recovery of mechanical integrity. Lack of catalyst leads to incomplete coverage, partial polymerization, and poor mechanical recovery. Catalyst availability is determined by the competing rates of dissolution of the catalyst and polymerization of the healing agent. First-generation Grubbs' catalyst exists in at least two crystal polymorphs, each with a distinct crystal shape, thermal stability, and dissolution kinetics. The more rapidly dissolving polymorph shows superior healing efficiency when used as the initiator in a self-healing epoxy material based on ring-opening metathesis polymerization of dicyclo-pentadiene.