Hydrogel Of Many Talents

This new hydrogel has it all: It’s moldable, transparent, environmentally friendly, easily synthesized, and, if cut, heals itself. Takuzo Aida of the University of Tokyo and colleagues prepared the material by simply mixing clay, sodium polyacrylate, and a dendritic macromolecule in water at room temperature (Nature 2010, 463, 339). Researchers have been eying hydrogels as potential substitutes for petroleum-based plastics and have produced some tough, transparent versions. The Aida group’s hydrogel is the first to combine these features with self-healing and moldable properties, they say. The hydrogel’s self-healing properties come from noncovalent bonding features of the dendrimer, a macromolecule with numerous tentacles bearing guanidinium ion groups on the ends. These groups readily stick to the clay. As a result, a fresh-cut surface of the gel quickly adheres to another, but loses its sticking power if left in open air for more than a minute. Additionally, the group reports, proteins suspended in the gel retain their biological activity, raising the possibility that reaction sequences could be designed by connecting blocks containing different enzymes.