Wallace Carothers conducted research at the DuPont Company that led to the discovery of two synthetic materials that radically transformed society through their versatility and utility: neoprene, a rubber analog, and nylon, a silk-like fiber. The advent of nylon freed manufacturers from dependence on natural fibers for the production of textiles; this development became increasingly significant during shortages of natural fibers, such as those experienced during World War II, when trade blockades made it impossible to access essential natural materials. The continued improvement of nylon has resulted in the tailoring of specific characteristics, such as insulation and water repulsion.
Wallace Hume Carothers is shown here in the early 1930s, demonstrating the elastic properties of neoprene.
Wallace Hume Carothers was born on April 27, 1896, in Burlington, Iowa, the eldest of four children. His mother was Mary Evalina McMullin, and his father, Ira Hume Carothers, taught at the Capital City Commercial College in Des Moines, Iowa, eventually ascending to the vice presidency there. Carothers attended public school in Des Moines, graduating from North High School in 1914. He then matriculated to Capital City Commercial College and completed the accounting curriculum in a mere year to graduate in 1915.
Tarkio College in Missouri granted Carothers teaching assistantships in English and commercial studies, thus underwriting his study of the sci-ences—particularly chemistry and physics. Carothers completed the entire chemistry curriculum by the time that Arthur M. Pardee, the head of Tarkio’s chemistry department, departed for World War I (Carothers did not qualify for military service due to his health), so the college appointed the undergraduate student to head the department. Carothers graduated with a bachelor of science degree in 1920.
Carothers completed a master’s degree in chemistry within the next year at the University of Illinois. Pardee, who had moved to the University of South Dakota upon his return from the war, persuaded his former student (and replacement) to teach chemistry there for a year, after which Carothers returned to the University of Illinois for doctoral study. He won the Carr fellowship, the highest award granted by the department of chemistry, to finance the writing of his dissertation under Roger Adams on aldehydes in reactions catalyzed by platinum. He earned his Ph.D. in 1924, and the university retained him to teach in the chemistry department. That same year, he also published his first paper, "The Double Bond," in the Journal of the American Chemical Society, applying physicist Irving Langmuir’s atomic concepts to organic chemistry.
In 1926, Harvard University hired Carothers as an organic chemistry instructor. After only three semesters there, Carothers was wooed by Charles Stine, research director for the DuPont Company, to join his fundamental research program as a director at the new Experimental Station in Wilmington, Delaware. What enticed Carothers away from one of the most prestigious institutions in the country was the prospect of conducting pure research supported by a team of postdoctoral associates using state-of-the-art equipment; furthermore, he would have no teaching duties, which had distracted him from his research.
Carothers and his team focused their research on acetylene, and by 1931, they had combined vinylacetylene with a chlorine compound to create a rubber analog, which DuPont marketed as "neoprene." However, Carothers had already conceived of the line of research that would earn him lasting fame. In a letter to Cornell University’s John R. Johnson dated February 14, 1928, Carothers outlined his theory of linear polymerization, or the stringing together of monomers into long chains, called macromolecules. He eventually published a series of 31 papers which presented this theory in its entirety and laid the foundation for polymer chemistry, a field that has had a profound impact not only on the world of science but also on mainstream society, which benefits immensely from these man-made fibers.
The disintegration of trade relations between the United States and Japan, its main source of silk, spurred Carothers and his colleagues to investigate the synthesis of an artificial fiber similar to silk. Toward this end, they developed the condensation reaction method of polymerization; Carothers honed this technique to distill the by-product of water, thereby preventing it from dripping back into the concoction and weakening it. He prepared a number of polyesters by this method, some of which seemed commercially unpromising, and some of which he stored in vials for future analysis.
Carothers married Helen Everett Sweet-man, an employee in DuPont’s patent division, on February 21, 1936. A little less than a year later, in January 1937, Carothers’s favorite sister, Isobel, who was a singer in the popular radio trio of Clara, Lu, and Em, died unexpectedly. Carothers, who was manic-depressive, fell into deep melancholia over the loss. Even the pregnancy of his wife could not buoy his spirits; he became obsessed with famous chemists who had committed suicide, and Julian Hill, a DuPont colleague, noticed a ration of cyanide in his briefcase. On April 29, 1937, Carothers administered himself a lethal dose of the poison and died in Philadelphia. His daughter, Jane, was born on November 27, 1937, half a year after his family had interred his ashes in Glendale Cemetery in Des Moines.
Carothers left behind him a legacy of 62 technical papers and more than 50 patents, enough to establish him as a significant contributor to science. However, his most significant contribution was only discovered posthumously, when DuPont tested the polyamide samples that Carothers had left in his lab. One, marked "Tiber 66" (after its dual-stranded structure containing six carbons on each side, created by the combination of adipic acid with hexamethy-lene-diamine), turned out to be a strong and versatile fiber, which DuPont marketed as "nylon" starting in 1938. Since then, DuPont has earned about $4 billion a year on this material that now sports innumerable diverse applications.
