Key to this technology is the analytical information provided by small angle neutron scattering (SANS) at ORNL's High Flux Isotope Reactor (HFIR).
The collaborative effort, headed by Joseph M. DeSimone of the University of North Carolina, was honored for the innovative use of carbon dioxide in polymerization (bonding of small molecules to form polymers) processes.
Carbon dioxide has long been considered desirable for industry use as a solvent because it is a cheap, essentially benign substance that presents no disposal problems. Today's processes create undesirable by-products such as chlorofluorocarbons, contaminated water and waste solvents. Until recently, CO2 had not been used as a solvent because few polymers are soluble in it. However, supercritical CO2, which exists at a temperature and pressure where differences between the gaseous and liquid state disappear, is a better solvent because it retains properties of a liquid (suspension of molecules) and a gas (high rates of reaction).
The team created new surfactants it suspected would dissolve in supercritical CO2 and form microscopic clusters called micelles, where polymers could form. The team applied highly penetrating neutron beams at HFIR to study micelles on a microscopic level and better understand how to make polymers "dissolve" in CO2.
"SANS now makes it possible to measure these processes in situ and is the premier technique for measuring polymers, either as molecules or in clusters such as micelles" says George Wignall, group leader of ORNL's Small Angle Scattering Facilities. "Many important issues in developing polymerization processes can now be explored and developed, leading to cleaner polymerization processes for industry use."
The researchers were honored at the National Academy of Sciences in Washington, D.C. June 24. The annual award is presented to five groups that apply fundamental or innovative chemical methods to accomplish pollution prevention and have broad industry applications. President Clinton introduced the Presidential Green Chemistry Challenge in 1995 as part of an initiative to "promote pollution prevention and industrial ecology through a new Environmental Protection Agency Design for the Environment Partnership with the chemical industry."
Research results from the team have been reported in Science and will appear in an upcoming issue of Nature.
Wignall has been a senior researcher and group leader of ORNL's Small Angle Scattering Facilities since 1979. Previously, he was a project leader at Imperial Chemical Industries (ICI) in Brussels, Belgium, and a senior research scientist at ICI Corporate Laboratory in Runcorn, England. He received his doctorate in physics from Sheffield University, England, is a fellow of the American Physical Society and received the Lockheed Martin Research Award in 1996 for sustained achievement on polymer structures using SANS. Wignall and his wife, Andrea, live in Oak Ridge. They have two children.
Cochran is a group leader in the Chemical Technology Division and adjunct professor in the Department of Chemical Engineering at the University of Tennessee. Cochran is a winner of the 1997 Lockheed Martin Energy Research Technical Achievement Award. He received his doctorate in chemical engineering at the Massachusetts Institute of Technology. He and his wife, Betsy, live in Oak Ridge. They have two children.
Londono is a postdoctoral researcher in the Chemical and Analytical Sciences Division and research assistant professor in the Department of Chemical Engineering at the University of Tennessee. Before that he was a researcher at Rutherford Appleton Laboratory/University of London. He received his bachelor's in physics and doctorate in crystallography from the University of London. He was part of a group in 1996 recognized for Outstanding Scientific Accomplishment in Material Chemistry from the DOE. Londono lives in Oak Ridge with his wife, Marie, and their two children.
ORNL, one of DOE's multiprogram national research and development facilities, is managed by Lockheed Martin Energy Research Corporation.