"You can get a surprisingly large amount of chemical energy from a polymer under compression," Grzybowski said. "This energy is, in a sense, free for the taking. Under normal circumstances, the energy is virtually never retrieved from deformed polymers, which then age unproductively. But you could recharge a battery from the energy produced by walking or driving a car. And you could capture even more energy when compacting millions of plastic bags."
Grzybowski is also director of Northwestern's Non-Equilibrium Energy Research Center, which is funded by the U.S. Department of Energy.
"We are interested in new sources of chemical energy, and this energy from the simple breaking of polymers' bonds is not being used," he said. "By surrounding the polymer with a medium, such as water, we can produce environmentally friendly chemical energy. One direction we are pursuing is to use this energy to sanitize water in developing countries. This is possible because hydrogen peroxide produced by squeezed polymers kills bacteria."
The researchers confirmed that mechanical deformation -- moderate squeezing -- created free radicals in the polymers. They also determined the number of radicals produced in a polymer under pressure is approximately 1016 (10 to the 16th) radicals per cubic centimeter of polymer -- a substantial amount.
They next filled polymer tubes with water, squeezed the tubes and measured the total number of radicals that migrated into the surrounding solution. They found that nearly 80 percent of the radicals made the trip.
Grzybowski and his team demonstrated they can squeeze a polymer, such as what might be found in a shoe, tire or plastic bag, and get a mechanical-to-chemical energy conversion of up to 30 percent -- approaching the energy efficiency of a car engine.
The hydrogen peroxide produce
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