Scientia: Research at the University of Tennessee
Stretching the Limits
By ASHLEY YEAGER
UT scientist Jimmy Mays is a polymer chef—some of his creations contribute to new energy sources; others may improve the performance of automobile tires and even the common rubber band
In a metaphoric sense, Jimmy Mays plays with food for a living.
“We make molecules that are like spaghetti,” says Mays, a Distinguished Scientist in chemistry with a joint appointment at the University of Tennessee and Oak Ridge National Laboratory. “They’re long molecules that can get tangled up with one another.” Mays says that these long molecules, known as polymers, make up much of our natural world. Hair, clothing, and many human body structures contain these stringy nanoparticles, and after studying natural polymer designs, Mays develops ideas for synthesizing new ones.
“Just like a chef might think of a new ingredient that might taste good, we think of a new ingredient that might perform a specific function,” he says. “We’re looking for ingredients that have unusual shapes or characteristics.”
Enter Mays’s Kitchen
Mays synthesizes these polymers in laboratories at UT and ORNL. Like most chefs, he uses a basic recipe when creating a new molecule and then experiments with it by making small changes in the formulation. Working with Mark Dadmun, another UT chemistry professor, the two begin by sketching the desired polymer’s structure, guided by the properties they want the polymer to have.
Dadmun says that the polymer’s surface properties are most important because that’s where the polymer interacts with other molecules. His job is to predict how they can control the molecules’ surface structure as Mays concocts the polymer. Such control allows the scientists to make new and better materials, among them, a membrane that will play a role in producing energy from hydrogen.
Hydrogen fuel cells have the potential to be lightweight, very low-pollution sources of energy. A hydrogen fuel cell is similar to a battery in which the hydrogen gas is stripped of its positively charged protons on the anode-side of a polymer membrane. The protons are transported to the cathode, where they react with oxygen to produce energy and water.
Power Play
The idea for the polymer membrane for the fuel cell struck Mays during a conversation with fellow ORNL scientist Mike Simonson. Mays’s colleague wanted to harvest energy from hydrogen but needed a polymer membrane that could function in a fuel cell’s electrically charged high-heat environment.
Intrigued by the challenge, Mays set to work. Combining ingredients from flasks of colorful polymer concoctions, he developed his concept by producing a filmy material to function in the cell. The Department of Energy has since rewarded Mays’s concept with a $1.5-million grant to further develop the membrane.
To build this polymer membrane, Mays began by mixing hydrogen and carbon to create chains of molecules that look like spaghetti strands. Then, he chemically modifies the polymer until he has a structure with the desired properties.
The Proof Is in the Polymer
Using chemistry-based tests, Mays determines whether his new polymer could withstand the high temperatures and the flow of charged particles present in the fuel cell. “Our structures are mostly solids—usually forming a filmlike material,” he says. “In fact, the material used for the fuel cell looks like black plastic wrap.”
Mays’s gift for polymer synthesis has attracted the attention of other UT and ORNL scientists. Just as Simonson approached Mays with an idea, other scientists frequently ask Mays if he can construct a molecule to perform a specific function; Mays and Dadmun then go to work on the sketches. “Sometimes a concept will look good on paper, but the chemistry won’t go the way you want it,” Mays says. “Either it doesn’t work, or, in some cases, you end up with something better.”
A Better Rubber Band
Mays’s elastomers are one example of such serendipity. These super-stretchy materials look like ordinary rubber bands, but they can stretch farther and retain their shape better than anything currently on the market.
Mays says that existing rubber bands and other elastomer products can stretch to about 10 times their normal size, but they don’t fully recover their original shape when the stretching force is removed. But Mays’s materials can stretch up to 16 times their original size and recover almost completely. “Think doctor’s gloves or any rubbery material that you can pull [out of shape] and then have it snap back,” Mays says. “The end result of this work might be better rubber bands or automobile tires.” Besides being fully functional, Mays’s elastomers can also be made recyclable—and that’s better in every way.
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For more information, contact Jimmy Mays, (865) 974-0747, e-mail jimmymays@utk.edu.