Green Alternative to Polymers
RESEARCH By Todd Morton, Ars Technica
Hydrogels are novel materials with properties unlike those of normal polymers, but their potential applications have remained limited to small niches. A team of researchers from Japan aims to change that, and has discovered a new approach to hydrogels that yielded a trifecta of increased mechanical strength, easy preparation, and possible green-tech implications.
Hydrogels, as the name should imply, are mostly water (as much as 99 percent), and have a consistency that is best described as - you guessed it - a gel. This makes them a great candidate for novel biomedical applications like time-released targeted drug delivery and artificial tissues, because we're mostly water, too. However, this makes them less useful for pretty much everything else outside of the body. They are often vulnerable to solvents and, as you might have noticed, there aren't many items that actively rely on Jell-O as a structural component.
The researchers turned what might be a problem into a solution. The large, branchy dendritic polymer macromolecule they were working with had a tendency to adhere quite strongly to glass. So the researchers investigated its interactions with clay, which shares some properties with glass. Using an additional chemical that disperses clay nanosheets in water, they were able to get their dendritic macromolecule to form a structural framework with the clay. The hydrophilic portion of the framework attracts and retains water molecules.
This notably improved mechanical properties over other hydrogels, as it could be molded into shapes that are free-standing and relatively robust and would undergo self-healing when cut. Less than 0.4 percent of it is petroleum-derived, so improved versions may provide an appealing green alternative to polymers. The best aspect, however, may be its simplicity: all you need are three ingredients, a beaker of water, and something to stir with.
Nature 463, 339-343 (21 January 2010). nature.com