William Dichtel is as much builder as chemist, combining molecules to create larger structures. But the work that made him a MacArthur fellow caught the mysterious selection committee’s eye as much for its empty spaces as its shape. That’s because Dichtel specializes in porous polymers: tiny structures that are mostly made of empty holes. If Dichtel has anything to do with it, those pores might someday put bomb-sniffing dogs out of business.
“These holes are roughly the same size as the molecules that make up the polymer,” he explains. “It would be normal for one gram of our material — about the weight of a dollar bill — to have the surface area of somewhere between an Olympic-sized swimming pool and a football field.”
The polymers that Dichtel creates in his lab at Cornell University are more than chemical curiosities. In fact, their holes are what make them such intriguing substances. Given such huge surface areas, they can reflect light, conduct electricity and store gases and other molecules. They can also amplify infinitesimal amounts of other chemicals, even when those chemicals are only contained in the air.
It’s that capacity that could eventually put bomb-sniffing dogs out of business. Dichtel explains that when they’re designed the right way, porous polymers can trap even the smallest traces of RDX and other “compounds of interest” — chemicals associated with landmines, IEDs and other weapons used by “people up to no good.” RDX is extremely powerful, but it’s also much harder to detect than TNT. That is, unless it comes up against wee porous polymers, which could someday be put in devices that detect the compounds.
The potential of these miniature marvels goes far beyond the battlefield. Recently, Dichtel has been spending his time figuring out how to turn them into the world’s tiniest water filters, sifting traces of things like pharmaceuticals and flame retardants out of water. “There are compounds in our life that protect us or have some biological function,” he says, but we don’t necessarily want them in the water we drink. Rather than rely on imperfect treatment options, why not rely on newfangled polymers instead? “High-surface polymers can outperform current technologies,” he says. His research group plans to publish an article on their water filtration findings soon.
It can be hard to wrap your mind around miniscule crystals made of lightweight elements and held together by tough chemical bonds. But really, you just need to envision a honeycomb to get the idea. Dichtel thinks of porous polymers as molecules “you can just program” to assemble bigger structures. “I think people can relate to them a lot,” he says. “They can see that it’s so obviously chemistry, but also how the shape of the molecule can give rise to other structures, too. It helps that they’re very beautiful. Humans love symmetry.”
Humans love adventure stories, too, and much of Dichtel’s work takes place on the cutting edge of research. Those take him into interdisciplinary territory, stretching his communication skills and pushing him to think about new ways to communicate about chemistry. “When you’re out there on the research frontier, sometimes the problems you face look like chemistry,” he says. “Sometimes they look like physics. Sometimes they look like other things.”
But just because Dichtel is tiptoeing along the boundaries of science doesn’t mean he’s doing it alone. “I think there’s a misconception about science that can be somewhat reinforced by the concept of a genius grant,” he muses. “I’m not here alone working in a room and coming up with a big idea.” In fact, he says, most of his work involves teaching his young colleagues how to tackle what he calls “the hardest problems they’ll ever encounter” — problems that skirt the edges of comfort, feasibility and even comprehension. “Science is a very social endeavor,” says Dichtel. Even if it contains lots and lots of empty space.