It is a challenge to synthesize materials that possess the properties of biological muscles—strong, elastic and capable of self-healing. Herein we report a network of poly(dimethylsiloxane) polymer chains crosslinked by coordination complexes that combines high stretchability, high dielectric strength, autonomous self-healing and mechanical actuation. The healing process can take place at a temperature as low as −20 °C and is not significantly affected by surface ageing and moisture. The crosslinking complexes used consist of 2,6-pyridinedicarboxamide ligands that coordinate to Fe(III) centres through three different interactions: a strong pyridyl–iron one, and two weaker carboxamido–iron ones through both the nitrogen and oxygen atoms of the carboxamide groups. As a result, the iron–ligand bonds can readily break and re-form while the iron centres still remain attached to the ligands through the stronger interaction with the pyridyl ring, which enables reversible unfolding and refolding of the chains. We hypothesize that this behaviour supports the high stretchability and self-healing capability of the material.
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This work was partially supported by the Major State Basic Research Development Program (Grant No. 2013CB922100 and Grant No. 2011CB808704), Air Force Office of Scientific Research (FA9550-15-1-0106) and Samsung Electronics. F.L. thanks the Swiss National Science Foundation for an Early Mobility Postdoc grant. We thank J. Ma for helpful discussions on the DFT calculations and X. R. Lu, J. C. Lai, X. Y. Jia and J. F. Mei for assistance in the synthesis and characterization of the model complex.
Stanford University has filed a provisional application for a patent based on this technology that names C.H.L., C.W. and Z.B. as inventors.
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Li, C., Wang, C., Keplinger, C. et al. A highly stretchable autonomous self-healing elastomer. Nature Chem 8, 618–624 (2016) doi:10.1038/nchem.2492
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