Can you see how the molecular structure of this macromolecule is similar to that of nylon? To save time we often draw it like this:

tetramethylurea

Kwolek had not been trying to invent a liquid crystalline material. She had hypothesized that a macromolecule with the structure you see above would produce very strong fibers. To test the hypothesis, she synthesized the macromolecule. But sometimes scientific inquiry turns up more than anyone expects. Before Kwolek could make her new polymer into fibers, she noticed that when this polymer was dissolved in tetramethylurea and calcium chloride (CaCl₂), the polymer molecules did something very strange. The Kevlar^® macromolecules, which were long, straight, and stiff, lined up like logs floating down a river. Kwolek could tell the macromolecules were lined up because of the strange opalescent look of the solution.

Kevlar^® molecules lined up in solution.

This is unusual because normally, molecules in a solution or a pure liquid aren't arranged in any orderly fashion. Molecules of solid materials are often arranged in orderly fashions called crystals. Since a Kevlar^® solution is a liquid, but its molecules are ordered, the solution is called a liquid crystal.

This was weird, all right, but what does it have to do with life outside the lab? It turned out that Kevlar^® could do some really amazing things. But before we talk about that, we're going to learn a little bit about the woman who invented this unusual stuff.

Next: Meet Stephanie Kwolek

Aramids — a guide to the amazing polymers Kwolek synthesized, part of The Macrogalleria from the University of Southern Mississippi.

Polymers & Liquid Crystals — an excellent tutorial and resource from Case Western Reserve University.

References

Kwolek, Stephanie. Interview by Bernadette Bensuade-Vincent, 21 March 1998 at Wilmington, Delaware. Philadelphia: Chemical Heritage Foundation.