Multi-stage polymer systems for the autonomic regeneration of large damage volumes

Recovery of catastrophic damage requires a robust chemistry capable of addressing the complex challenges encountered by autonomic regeneration. Although self-healing polymers have the potential to increase material lifetimes and safety, these systems have been limited to recovery of internal microcracks and surface damage. Current technologies thereby fail to address the restoration of large, open damage volumes. A regenerative chemistry was developed by incorporating a gel scaffold within liquid healing agents. The healing system undergoes two stages, sol-gel and gel-polymer. Stage 1, rapid formation of a crosslinked gel, creates a synthetic support for the healing agents as they deposit across the damage region. Stage 2 comprises the polymerization of monomer using a room temperature redox initiation system to recover the mechanical properties of the substrate. The two stages are chemically compatible and only react when a specific reaction trigger is introduced -- an acid catalyst for gelation and initiator-promoter for polymerization. Cure kinetics, chemical and mechanical properties can be tuned by employing different monomer systems. The versatile gelation chemistry gels over 20 vinyl monomers to yield both thermoplastic and thermosetting polymers. The healing efficacy of the two-stage system was studied in thin, vascularized epoxy sheets. By splitting the chemistry into two low viscosity fluids, we demonstrated regeneration of gaps up to 9 mm in diameter. The combination of microvascular networks and a new healing chemistry demonstrates an innovative healing system that significantly exceeds the performance of traditional methods.