For immediate release: September 27, 2002.
For more information, contact Susan Griffith, 216-368-1004 or sbg4@po.cwru.edu

CLEVELAND—Molecular electronics got a boost with the discovery of a new class of liquid crystalline materials that has potential use in electronic devices such as light emitting diodes (LED), solar cells, optical switches and transistors.

The new molecules are called supramolecular helical dendrimers.

The molecules making up liquid crystal are based on highly branched polymers called dendrimers that assemble themselves into arrays of semiconducting columns, each with a structure reminiscent of DNA. The high degree of molecules' abilities to organize leads to efficient transport of electrical signals.

Kenneth Singer, Case Western Reserve University professor of physics; Virgil Percec, University of Pennsylvania professor of macromolecular chemistry; and a team of researchers described these dendrimers, their structures and properties in the September 26th Nature article, "Self-organization of supramolecular helical dendrimers into complex electronic materials."

Interest in organic materials as electronic materials has grown rapidly with the introduction of electronic displays made from luminescent organic crystals and polymers. Highly organized fluids, such as those described in the Nature article, combine the important properties of efficient electrical transport with the ability to easily and cheaply produce devices.

These new materials represent a significant advance in that they allow unprecedented flexibility in the design of materials to be custom-tailored in order to precisely match the electronic function needed, according to Singer.

"The dedrimers are very robust at driving self-assembly of arrays of columns, seeming to almost grow themselves into electronic devices," he said. "This property enables the self-organization of nearly any electronically active molecule, even ones that would never be expected to organize in such an ordered array.

"This concept might enable a new generation of low-cost, light-weight and easier to produce electronic devices," added Singer, whose lab conducted the measurements of the electrical properties of the dendrimers.

Over the past five years, Singer collaborated with Percec, who is a pioneer in dendrimers and was responsible for advancing the material concept. Dendrimers are molecules with branched tails of hydrocarbons and fluorocarbons. These tails link to the electronically functional molecules and force them to stack like poker chips in a column, enhancing their electronic interactions. The columns then self-organize into an ordered array.

"This concept is particularly exciting since one can imagine the same material forming a device made from a single molecular column up to a gigantic array of columns the size of computer screens," Singer said.

The research by Singer and Percec, who was a former faculty member in macromolecular science at CWRU, has the support of a grant from the U.S. Air Force's Office for Scientific Research.

Other collaborators are Irina Shiyanovskaya from CWRU's physics department; Martin Glodde, T.K. Bera, and Y. Miura from Penn's chemistry department; V.S. K. Balagurusamy and Paul A. Heiney from Penn's department of physics and astronomy; A. Rapp and H. W. Spiess from the Max Planck Institute for Polymer Research in Germany; and S. D. Hudson and H. Duan from the National Institute of Standards and Technology in Maryland.

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