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ORNL discovery may lead to new thinking, materials

OAK RIDGE, Tenn., March 30, 1999 -- Oil and water do mix after all, some chemists at the Department of Energy's Oak Ridge National Laboratory have discovered, and their finding may lead to new advanced materials and have other ramifications.

The key to their discovery lies in a technique involving micro-droplets of an evaporating solution. This process allows chemists to work at the molecular level with a variety of chemical compounds called polymers, which make up many of the products we use every day. By working with these minuscule particles, the chemists can blend two polymers within a single micro-particle, provided that the initial droplet is less than 10 micrometers in diameter.

"For small droplets of a solution, solvent evaporation takes place quickly enough to inhibit phase separation, producing dry polymer blend particles that have uniform structure to within molecular dimensions," said Mike Barnes of ORNL's Chemical and Analytical Sciences Division. "It's kind of like putting football fans of crosstown rivals in a huge room where they normally wouldn't mix, and then shrinking the room into the size of a phone booth before the fans can separate."

In addition to the academic significance of this discovery, the finding clears the way for development of new materials in the form of bulk composites and blends that can be used for coatings, opto-electronic components, magnetic media, ceramics and special materials, micro- or nano-manufacturing and bioengineering. The researchers see first applications in sophisticated drug delivery systems.

"Eventually, we believe this will lead to new high-strength materials, better paints and coatings and a number of other consumer products," said co-developer Don Noid of ORNL. "Initially, though, we see this technology being used to carry specially engineered molecules into cells within the body as part of medical treatments."

The discovery grew out of a basic energy science effort to probe single molecules. "There is great interest in isolating and manipulating single molecules," Barnes said, "and that's why we developed the droplet approach."

The different backgrounds of ORNL's Barnes, Noid and Bobby Sumpter and collaborator Joshua Otaigbe of Iowa State University also played an important role in the discovery. While Barnes' background is in the laboratory, Noid and Sumpter have expertise in computational modeling. Otaigbe is an expert in materials properties and characterization of polymer powders and it was through working with him that the importance of polymeric particles came to light.

The combination of expertise in theory and practical experience helped in developing the micro-droplet technique for polymer particle generation, Sumpter said. In addition, this finding, published in the Feb. 1 issue of Optical Society of America's "Optics Letters," could provide some new tools for understanding how to make composite materials from immiscible polymers.

"We use computational tools to study the properties of the experimentally generated nanoscale polymer particles," Sumpter said. "These simulations can provide useful insights to interpret the experimental data and behavior of ultra-fine polymer particles in new materials and devices."

The research was funded by DOE and the Laboratory Directed Research and Development program, an internal source of funding, at ORNL.

ORNL is a DOE multiprogram research facility managed by Lockheed Martin Energy Research Corporation.

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category: materials, physical sciences