A way to efficiently repair cuts and cracks in polymers via the formation of new, strong carbon-carbon bonds has been devised by chemists at the University of California, Irvine (J. Am. Chem. Soc., DOI: 10.1021/ja306287s). Yi-Xuan Lu and Zhibin Guan came up with the strategy, which makes use of the olefin metathesis reaction to shuffle C=C bonds at the fracture interface of cross-linked polybutadiene. The researchers introduce a small amount—as little as 0.005%—of Grubbs second-generation ruthenium metathesis catalyst into the polymer. Wherever the polymer is cut, healing occurs by simply pressing the two fracture surfaces together with moderate pressure (10 to 30 kilopascal) and then waiting. The catalyst-loaded polymer repairs itself at temperatures as low as 5 °C, although it takes longer than healing at ambient temperature. Lu and Guan also show they can use the metathesis reaction to repair ruthenium-free cross-linked polybutadiene by simply applying a small amount of the catalyst to the fracture surfaces and pressing the wound shut. “The approach is simple, effective, and potentially applicable to a wide range of olefin-containing polymers such as polyisoprene, butyl rubber, polynorbornene, and other polymers containing double bonds amenable for metathesis,” they note.