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