Self-healing materials

Note The ability of the M-NHC bond to reform even after reductive elimination of an imi-dazolium salt is the key property in the development of electrically conductive, self-healing materials from these ligands. 

A scanning electron microscope image showing the fractured plane of a self-healing material with a ruptured microcapsule in a thermosetting matrix. 

Self-healing materials should have many applications. The U.S. Air Force, which partially funded the research at UIUC, is interested in using the materials in tanks that hold gases and liquids under pressure. The current materials used for these tanks are subject to microcracks that eventually grow, causing the tanks to leak. Self-healing materials would also be valuable in situations where repair is impossible or impractical, such as electronic circuit boards, components of deep space probes, and implanted medical devices. ... 

Other considerations Self-healing material in the reduced state Cr(VI) can be present Inexpensive material Insensitive to sulfur used to polish sulfur to very low levels Needs to be carefully reduced Self-healing material in the active (i.e., reduced) state Deactivates by water condensation and air exposure Needs careful discharge from the reactor (self-healing catalyst) Reaction is diffusion limited Insensitive to start-stop and air exposure No need for pre-reduction Kinetics limit usefulness of the catalyst below 250° C... 

In addition, there is also the possibility of tailoring the properties of plain composites further by adding particles (such as metallic fillers [29,30], carbon nanotubes [31] or urea formaldehyde [32]) to the composite layers to create multifunctional and self-healing materials, von Klemperer and Maharaj [29] added copper and aluminium powder fillers to carbon fibre epoxy laminates to improve the electromagnetic shielding capacity of the composite panels. Blast tests on the laminates [30] showed that the laminates with filler particles outperformed their plain composite counterparts, although the margin was small. 

Wool, R. R, Self-healing materials a review, Soft Matter, 4, 400-418 (2008b). 

Toohey, K.S. Sottos, N.R. Lewis, J.A. Moore, J.S. White, S.R. Self-healing materials with microvas-cular networks. Nature Materials 6(8), 581-585, 2007. 

Zhu, G. Lu, L. Tang, J. Dong, B. Han, N. Xing, F. Prepararion of mono-sized epoxy/MF microcapsules in the appearance of polyvinyl alcohol as co-emulsifier. Proceedings of the Fourth International Conference on Self-Healing Materials, Ghent, 2013, pp. 225-228. 

Yu X, Chen L, Zhang M, Yi T (2014) Low-molecular-mass gels responding to ultrasound and mechanical stress towards self-healing materials. Chem Soc Rev 43 5346-5371... 

Responsive Polymers as Sensors, Muscles, and Self-Healing Materials... 

Keywords Artificial muscles Mechanochemistry Responsive polymers Self-healing materials Sensors... 

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