NEWS

By DAVID WILLIAMSON
UNC News Services

CHAPEL HILL -- University of North Carolina at Chapel Hill researchers have proven the existence of a long-sought-after chemical structure, or configuration, known as the biaxial nematic phase. Some earlier chemists did not believe that such an alignment of molecules could exist.

In work that might one day revolutionize liquid crystal displays (LCDs),
Dr. Edward T. Samulski, professor of chemistry, and his students found unequivocal evidence of a biaxial structure in nematic liquid crystals – a scientific achievment that has eluded researchers for more than 30 years.

The discovery of biaxial nematics could lead to more efficient LCDs with far lower power consumption, Samulski said.

"In 1970, IBM's Dr. Marvin Freiser predicted that some flat liquid crystal molecules could form a phase where both the sides of the molecules would be aligned, as well as being roughly parallel to one another lengthwise," he said. "Such a phase, if it existed, would actually constitute a new state of matter. Over the intervening years, scientists attempted to find experimental proof of Freiser’s prediction to no avail."

Under Samulski¹s direction, former graduate student Theo Dingemans created a new class of bent, boomerang-shaped molecules that they thought might form a biaxial nematic phase. Then, postdoctoral fellow Louis Madsen modified a spectrometer that could capture signs of such a structure in liquid crystal. His high-temperature nuclear magnetic resonance probe finally showed that Dingeman¹s new class of bent molecules indeed formed a biaxial phase.

A report on the discovery appears this month in Physical Review Letters, a scientific journal. Madsen and Samulski were the principal investigators. Graduate student Michi Nakata, who was visiting from Japan, also participated in the work.

Further evidence that the UNC team succeeded came from a team of scientists at Kent State University headed by physics professor Satyendra Kumar. Working with Samulski¹s compounds, his group confirmed that the molecules aligned along two axes by projecting X-rays through the liquid crystal and examining the resulting diffraction patterns.

Their report was published in the same issue of Physical Review Letters.

"This is a new state of soft matter, and it's important from a fundamental point of view, but it might also have technological applications," Samulski said. "On paper, it looks like it could create faster liquid crystal displays."

The UNC chemist said he and his students are not themselves investigating applications since they are basic -- not applied -- scientists.

"In a practical sense, to get this to work in everyday devices, it would have to function at room temperature," he said. "Our materials are liquid crystals at nearly 200 degrees Centigrade, so there is a long way to go."

That is a technical hurdle likely to be overcome by others one day, he said. "The fact that we have proven that this kind of liquid crystal can exist should inspire other chemists to try to make similar molecules that would be liquid crystals at room temperature," he said. "Still, people have been working in this area for some 35 years, and it's very pleasing to show that this theoretical possibility in fact exists."

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Note: Samulski can be reached at (919) 962-1561 or et@unc.edu.