Wallace Hume Carothers

The American chemist Wallace Hume Carothers (1896-1937) was an experimentalist in the organic and industrial branches. His researches into polymerization led to the invention of nylon, the first truly synthetic fiber.

Artificial fibers, in the sense of being man-made, had been known since the closing decades of the 19th century; the first patents for processes resulting in fibers of the type later known as rayon were taken out as early as 1885. Once it had been discovered by x-ray analysis that natural fibers were composed of molecules that were themselves long and narrow, the possibility of building up such long molecules from small units, so producing new fibers, had been envisaged. Wallace Carothers, who more than anyone enabled this possibility to be realized, died the year before the creation of nylon was announced by E. I. du Pont de Nemours and Company, whose research team he had led with such distinction.

Carothers was born on April 27, 1896, in Burlington, lowa, to Ira Hume Carothers, teacher of commercial subjects, and Mary McMullin Carothers. In 1915 he entered Tarkio College, Mo., specializing in chemistry. After the outbreak of World War I he was asked to teach chemistry, no experienced instructor being available. After he obtained his bachelor of science degree in 1920, he enrolled in the chemistry department of the University of Illinois.

In 1921-1922 Carothers taught analytical and physical chemistry at the University of South Dakota. About this time he began to pursue independent research problems. He became interested in the recent valency theory of lrving Langmuir and investigated its relevance to organic chemistry. After receiving his doctorate in 1924 for research on the reduction of aldehydes with a platinum catalyst, he stayed on at Illinois for 2 years, teaching organic chemistry, and in 1926 moved to Harvard.

In 1928 the Du Pont Company, which had planned a new program of fundamental research, selected Carothers to lead the team in organic chemistry at its experimental station at Wilmington, Del. He was allocated a small group of trained research chemists to work on problems of his own choice. In the 9 years that followed, he made several major contributions to fundamental theory, as well as laying the foundations for the development of new materials.

Synthetic Rubbers

After the discovery in the 19th century that rubber on heating yields the liquid hydrocarbon isoprene, it gradually became apparent that its molecules were long chains of isoprene units; attempts to polymerize isoprene, however, merely produced sticky, rubbery substances of no commercial value. The exhaustive studies of acetylene compounds made by Carothers's team led to the crucial step about 1931, when they found a workable process for converting the hitherto little-known and unstable substance monovinyl acetylene to chloroprene (closely related to isoprene). This, on polymerization, yielded what is now known as neoprene, superior in many respects to the natural product.

Discovery of Nylon

Carothers's greatest accomplishment was his work in the related field of polycondensation, that is, the linkage of pairs of compounds, instead of identical units, with the elimination of some simple substance such as water. He prepared a number of polyester fibers, but these seemed to be unpromising, chiefly owing to their low melting points (later, however, this road led to Dacron and Terylene). The polyamide Carothers produced from adipic acid and hexamethylenediamine was eventually selected by Du Pont's textile experts for development and became known as Nylon-66 ("six-six"), since each of the constituent molecules contains six carbon atoms.

Carothers was elected to the National Academy of Sciences in 1936. He suffered from periodic fits of depression, which steadily grew worse; during one of these he ended his own life.

Further Reading

• Roger Adams wrote a short biography of Carothers which was published in the National Academy of Sciences, Biographical Memoirs, vol. 20 (1939); this biography, slightly shortened and lacking the bibliography of Carothers's papers, is reprinted in Eduard Farber, ed., Great Chemists (1961). The development of synthetic rubbers and fibers, including the work of Carothers, is discussed in John Jewkes, David Sawers, and Richard Stillerman, The Sources of Invention (1958), and in James G. Raitt, Modern Chemistry: Applied and Social Aspects (1966); both books give useful references for further reading. For a history of chemistry which includes the work of Carothers see Aaron J. Ihde, The Development of Modern Chemistry (1964).
• Hermes, Matthew E., Enough for one lifetime: Wallace Carothers, inventor of nylon, Washington, D.C.: American Chemical Society, 1996.