Energy Squeezed Out Of Polymers

Generating chemical energy to run reactions in the lab could be as easy as squeezing a spongy stress ball, according to researchers at Northwestern University. H. Tarik Baytekin, Bilge Baytekin, and Bartosz A. Grzybowski have shown that, by compressing polymers in contact with water, they can generate hydrogen peroxide to drive various reactions at a mechanical-to-chemical energy conversion efficiency of up to 30% (Angew. Chem. Int. Ed., DOI: 10.1002/anie.201108110). By comparison, typical power plants generate energy with 30 to 40% efficiency. When polymers are compressed, some of their bonds cleave homolytically, generating radicals. If water is present at the polymer surface, H₂O₂ is produced when the radicals diffuse to the interface. The researchers demonstrated this mechanochemical phenomenon by injecting an aqueous solution of a nonfluorescent boronic ester of 7-hydroxycoumarin into the sole of a sneaker. After being walked on for two hours, the polymeric sole fluoresced brightly, indicating the generation of H₂O₂ and the compound’s subsequent cleavage of the boronic ester and release of the fluorescent 7-hydroxycoumarin. “When you look at all the polymers out there—in car tires, soles, and plastic bags—just aging unproductively, it is such a wide-open opportunity for energy retrieval,” Grzybowski says.