Gap-filling fluids for materials regeneration

GAP-FILLING FLUIDS FOR MATERIALS REGENERATION

J.S. Moore 1,5

1 _{Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL, 61801,}

USA – email: turchyn@illinois.edu

2 _{Department of Materials Science and Engineering, University of Illinois at}

Urbana-Champaign, Urbana, IL, 61801, USA.

3 _{Department of Theoretical and Applied Mechanics, University of Illinois at}

Urbana-Champaign, Urbana, IL 61801, USA.

4 _{Department of Aerospace Engineering, University of Illinois at Urbana-Champaign, Urbana,}

IL, 61801, USA.

5 _{Beckman Institute of Advanced Science and Technology, University of Illinois at}

Urbana-Champaign, Urbana, IL, 61801, USA – email: jsmoore@illinois.edu

Keywords: self-healing, large damage volume, regeneration, polymer network gel, free radical polymerization

ABSTRACT

Robust schemes for autonomic regeneration present challenging problems that demand new concepts in healing agents. The challenges arise from the interplay of mass transport and the forces, both intrinsic (e.g. surface tension) and extrinsic (e.g. gravity), that act upon liquid healing agents as they traverse the zone of regeneration. We demonstrate a cross-linked polymer gel as a synthetic scaffold for large damage volume regeneration and subsequent in situ post-polymerization for recovery of mechanical properties. The bi-phase chemical resin undergoes two independent autonomic transformations that are tunable and chemically compatible. In contrast to high viscosity epoxies, the resin begins as a two-component, low viscosity sol state. The scaffold material forms by acid-catalyzed gelation of an aldehyde cross-linker and functionalized oligomer in liquid monomer. The second transformation, occurring after gel formation, is a free-radical polymerization  of  the  gel  monomer  “solvent”  for   several orders of magnitude increase in modulus. Each phase, gelation and polymerization, can be independently adjusted to accommodate multiple healing configurations. Preliminary results suggest that careful timing of these chemical changes make it possible to fill large damage volumes with restorative materials without loss of healing agent.

Unlike photopolymerizations or high temperatures required in other curing systems, the bi-phase resin cures autonomously and under ambient conditions. The room temperature cure is accomplished using the promoted decomposition of a peroxide initiator with a metal-salt. Although oxygen inhibition is a common problem with free-radical polymerization, thiol-ene chemistry has shown great effectiveness in ambient cures. The combination of the gel scaffold with post-polymerization defines a new type of healing chemistry and further expands the healing capability of microvascular composites.