CU chemist reports on new material production

Geoffrey Coates, assistant professor of chemistry and chemical biology, and his colleagues have harnessed CO2 feedstock, used by plants, to make synthetic polymers. Frank DiMeo/University Photography

By David Brand

By mimicking nature, a Cornell chemist has found a seemingly efficient way to create a new plastic material. It would be either biodegradable or able to react with water to convert into nontoxic materials, and it would have properties such as impact resistance.

The natural system being copied is photosynthesis, nature's efficient way of extracting carbon dioxide (CO2) from the atmosphere and turning it into both monomers and polymers in the form of sugars and polysaccharides. The breakthrough is tapping the same CO2 feedstock used by plants to make synthetic polymers.

The advance reported at the American Chemical Society meeting this week by Geoffrey Coates, assistant professor of chemistry and chemical biology, and his colleagues at Cornell is a zinc-based catalyst used to react CO2 and epoxide molecules to produce a class of materials called polycarbonates.

An epoxide is a three-membered ring molecule, such as ethylene oxide. The resulting complex has an activity that is significantly higher than any previous catalyst in copolymerizations of CO2, Coates said. This means that for the first time the process appears to be economical and have commercial possibilities.

One catalyst looks particularly promising, consuming more than 600 CO2 molecules an hour, Coates said. "We are at the point at which reactions now only take hours, compared to days for previous catalysts."

Coates noted that the new polymer has potential application as a biodegradable material in packaging or in agricultural or biomedical materials. Difficulty of manufacture has, to date, yielded such small amounts of the polymer that a comprehensive study of its properties has not been made. However, Coates said, because of the low cost and accessibility of CO2 and the attractive properties of polycarbonates, "the development of new, efficient catalysts for the polymerization process is a significant scientific goal."

Coates was assisted in this research by Cornell graduate student Ming Cheng and staff crystallographer Emil Lobkovsky.