perkin medal
able quantities of ether and hydrogen chloride gas in the middle of a hot and humid Delaware summer," she recalls. From there, she worked on lowtemperature polymerization to reach high molecular weights. And she arrived at the right solvent for the resin, aqueous tetramethylurea and lithium chloride. "But here was a surprise," she says. "When I dissolved the PBA polymer at 10% concentration in tetramethylurea with 6.5% LiCl, the solution was unusually fluid (low viscosity), turbid, stir-opalescent [opalescent when stirred], and buttermilk-like in appearance. "Conventional polymer solutions are
matter that would plug the holes of the spinneret." Kwolek persisted in getting the fiber spun, though, and the fiber turned out to be extremely strong without any optimization, with a modulus (measure of stiffness) of 430 g per denier (gpd). A denier is a unit of fineness of fiber, such that 1 g per 9,000 meters is 1 denier. By comparison, glass fiber has a modulus of 300 gpd, DuPont's Nomex brand of poly-m-phenyleneisophthalamide has 100 gpd, and textile polyester has 70 gpd. Kwolek's first thought was surprise at having reached such heights of modulus and tensile strength. But her second thought was anxiety about speedy filings for patents. "You know that if you've thought about something, then somebody else has probably thought about it too," she explains. It is Kwolek who will receive the Perkin Medal this Wednesday night at a dinner in New York City. But as she tells
usually clear or translucent and have the viscosity of molasses, more or less. The solution that I prepared looked like a dispersion but was totally filterable through a fine-pore filter. This was a liquid crystalline solution, but I didn't know it at the time. "This solution gave me considerable trouble, because the person in charge of the spinning unit refused to spin a cloudy polymer solution that he said, 'flowed like water.' Furthermore, he was afraid that the cloudiness of the solution indicated the presence of particulate
stories from those pioneering days, she makes it clear that she was surrounded and supported by numerous coworkers. She speaks of laboratory directorJohn Griffing, who thought the future lay with "intractable" polymers. Paul Morgan and Eugene E. Magat were among those who pushed the poly-^-phenyleneterephthalamide effort. And Joseph Rivers developed the test methods to evaluate fibers for end uses in radial tire cord, composites, rope, thermal insulating clothing, and bulletproof vests. Stephen Stinson
Stephanie Kwolek Wins 1997 Perkin Medal
S
tephanie L. Kwolek, a retired chemist from DuPont, wiJl receive the 1997 Perkin Medal for her outstanding achievements in applied chemistry. She is only the second woman to receive the prize in its 91-year history. The medal especially recognizes her inventions of liquid-crystal aromatic polyamides. In particular, her pioneering research on poly-^-aminobenzamide (PBA) resin and fibers paved the way for understanding of that liquid crystalline polymer and for the development of polyp-phenyleneterephthalamide, which DuPont markets under the trade name Kevlar. The American Section of the Society of Chemical Industry awards the Perkin Medal annually to an outstanding chemist chosen by officers of the Society of Chemical Industry, the American Chemical Society, the Electrochemical Society, the American Section of the Société de Chemie Industrielle, and the American Institute of Chemists. Stephanie Louise Kwolek was born in 1923 in New Kensington, Pa. She received a bachelor's degree from Carnegie Institute of Technology, Pittsburgh, in 1946. She joined DuPont's textile fibers department in Buffalo, N.Y., in 1946 as a chemist and rose through the ranks to research associate at the company's experimental station in Wilmington, Del., before her retirement in 1986. As Kwolek recalls: "In 1964, I was asked to scout for the next-generation fiber. Nylon, Dacron polyester, Lycra spandex, and Nomex aramid had already been commercialized by DuPont. Now, high-performance fibers from intractable polymers became the goal." In the case of PBA, the problem was making pure intermediates and reaching high molecular weights. Reactive intermediates tended to hydrolyze or prematurely polymerize. Her solution was to treat ^-aminobenzoic acid with thionyl chloride. This gave a purifiable intermediate, p-sulfinylaminobenzoyl chloride (0=SNH-C6H4-C0C1). She dissolved the purified intermediate in diethyl ether and bubbled hydrogen chloride into the solution to obtain jD-aminobenzoyl chloride hydrochloride. "This was not particularly easy with a reaction involving consider-
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