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Polymers can fulfill a wide variety of functions thanks to properties such as high strength, solvent resistance and insulation. Now scientists have manufactured a polymer that seems to have an additional and unique attribute: it can mend itself without outside help. According to a report published today in the journal Science, cracks in the material can be repaired indefinitely through relatively simple heating and cooling conditions.
At room temperature and below, the polymeric substance is hard and fully transparent, with mechanical properties similar to those of some existing commercial resins. When heated to temperatures above 120 degrees Celsius, however, bonds between the individual units (termed monomers) begin to break. But when the material is later cooled, the bonds reform. Xiangxu Chen of the University of California at Los Angeles and his colleagues decided to probe this intriguing property and tested whether a solid block of the polymer could fully recover from a fracture rendered by a fresh razor blade.
The researchers clamped the resulting two sections of the solid polymer together, heated them for two hours to temperatures between 120 and 150 degrees C and let them cool to room temperature. They report that "the fracture healed almost completely to produce a homogenous material with a few minor defects, suggesting remarkable mending efficiency." What is more, the team determined that the material can heal itself efficiently a number of times. Although some of the polymer's properties still need improvement, the scientists suggest that it may be useful for applications such as self-mending packaging for electronics.
