August 2001

From Virginia Tech

Researchers develop ultra-thin heat protective coatings for rockets, insulating coatings for microelectronics

(Blacksburg, Va., Aug. 27, 2001) -- What if you could protect surfaces from extreme heat with coatings many times thinner than the surface of a soap bubble? You could increase the load capacity of rockets and jets. The U.S. Air Force is betting it can be done.

Virginia Tech researchers will report dramatic discoveries in designing such materials at the 222nd national meeting of the American Chemical Society, Aug. 26-30 in Chicago.

A Virginia Tech - Air Force research team lead by chemistry professor Alan R. Esker has studied very thin films of hybrid organic/inorganic molecules (polyhedral oligomeric silsequioxanes -- or POSS -- derivatives) that can be converted to a heat and fire resistant coating. The organic part of the molecule is burnt off to leave behind an inorganic polymer less than two nanometers thick (a nanometer is about the size of 10 atoms, or a billionth of a meter).

"The composites are used in engines," Esker says. "The Air Force is testing them as a coating for the cone where the exhaust comes out of rockets. The aim is to reduce weight, which improves fuel efficiency and allows for a bigger pay load in space."

Wherever possible, airplanes and rockets are assembled with adhesives rather than bolts and screws for weight reduction. The researchers have been looking at different organic groups to control the compatibility of the POSS molecule with the polymers used as adhesives, and to control other attributes of the molecule.

"Whether or not you get something that is homogeneous depends on the organic groups," says Esker. The organic component affects how you process the materials and the final properties, such as transparency for optical coatings or conductivity for microelectronic coatings. Other applications are spin-on glass for dielectric (insulating) coatings.

The Virginia Tech researchers are taking a unique approach to studying the morphology or distribution of POSS blended with polymers. They are the first group to study the compounds as "soaps." The organic/inorganic molecule looks like a cube. "We take a cube, which is hydrophobic, and break it to get something that is partially hydrophobic and partially hydrophilic," Esker explains. "It's a surfactant, like soap, so it will assemble on the air-water interface as a monolayer one to two nanometers thick."

The researchers will report on the dramatic differences in the morphology resulting from various POSS-polymer blends due to differences in surface chemistry of both the POSS and the polymer.

The paper, "Morphology of polymer/POSS blends at the air/water interface (MTLS 11)," will be presented by Esker at 2 p.m. Monday, Aug. 27, as part of the symposium on "3-D Silicon-Oxygen Cages (Polyhedral Oligomeric Silsesquioxanes): Materials for the 21st Century" in room S106A, Level 1 of McCormick Place South. Authors of the paper are Catherine E. Farmer of Buford, S.C., a recent master's degree recipient at Virginia Tech; Brent Viers of the Engineering Resource Center /PRSM, Air Force Research Laboratory; and Esker. Very recent results from work by a Virginia Tech undergraduate, Joe T. Polidan and another Virginia Tech graduate student Jianjun Deng will also be presented.

PR CONTACT: Susan Trulove
540-231-5646 STrulove@vt.edu












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