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PUBLISHED ONLINE: 18 APRIL 2016 | http://dx.doi.org/10.1038/nchem.2492
Web End =DOI: 10.1038/NCHEM.2492
Cheng-Hui Li1,2, Chao Wang1,3, Christoph Keplinger4,5,6, Jing-Lin Zuo2, Lihua Jin7, Yang Sun8, Peng Zheng2, Yi Cao8, Franziska Lissel1, Christian Linder7, Xiao-Zeng You2 and Zhenan Bao1*
It is a challenge to synthesize materials that possess the properties of biological musclesstrong, 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 signicantly 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 pyridyliron one, and two weaker carboxamidoiron ones through both the nitrogen and oxygen atoms of the carboxamide groups. As a result, the ironligand 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.
Animal muscle is a biomaterial that has long fascinated the scientic world: it is strong, elastic and able to undergo self-healing when wounded. Synthetic polymers have been
designed to self-heal by encapsulating healing agents or incorporating dynamic bonds13. However, most of these approaches require the input of energy (either heat or light)46 or the assistance of a liquid monomer and catalyst7, solvents8 or plasticizers9. Of the few examples of autonomous self-healing rubbers, most are based on moisture-sensitive hydrogen bonding1015, and therefore lack stability against moisture.
We describe herein a design concept that takes advantage of the versatility in tuning the strength of metalligand interactions to achieve high strength, high stretchability and room-temperature self-healing that is not signicantly affected by surface ageing (which occurs when a surface is exposed to air for some time without protection). Previous work that involved metalligand interactions for self-healing materials either relied on strong bonds, which required an external stimulus for healing4,1620, or
weak bonds, which could not provide sufcient mechanical strength21,22. To combine autonomous and reversible healing at room temperature, a weak bonding strength is...