Carothers, Modern Polymer Science, and the Development of Nylon

Wallace Carothers

In late 1926, Charles M. A. Stine, director of the E.I. du Pont de Nemours and Company's chemical department in Wilmington, Delaware, convinced the company's executive committee to establish a continuing program in fundamental research. Only a handful of industrial firms had such farsighted programs. For most firms, research simply meant problem solving and process improvement. But Stine proposed what he called "a radical departure from previous policy" - a program of "pure science" with "the object of establishing or discovering new scientific facts" without obvious practical applications. Stine argued that DuPont's support of work in pure science would enhance the company's prestige, make recuiting Ph.D. scientists easier, and cement bonds to academic chemistry departments. Finally, he added, something of practical value might come out of it.

Stine chose five lines of study -- colloid chemistry, catalysis, the generation of chemical and physical data, organic synthesis, and polymerization -- and set out to recruit the very best chemists to head each field. In 1927, he persuaded Wallace H. Carothers, a brilliant young instructor in organic chemistry at Harvard University, to head the program in organic synthesis.

Wallace Carothers was born in Burlington, Iowa, on April 27, 1896, the son of Presbyterians of modest means. His father taught at the Capital City Commercial College in Des Moines, Iowa, and young Carothers spent a year there. In 1915 he enrolled at Tarkio College, a small Presbyterian-supported school in northwestern Missouri. There he majored in chemistry while helping in the school's floundering commercial department. When the chemist who ran the college's one-man science department departed in 1918, Carothers, then a senior, took over the college's chemistry classes.

After graduating from Tarkio in 1920, Carothers continued his studies at the University of Illinois, at the time the preeminent school in the United States for training organic chemists. There, he earned a Master's degree in 1921 and a Ph.D. under Roger Adams in 1924. Years later, Adams characterized Carothers as "the best organic chemist in the country."

While an instructor at Illinois, Carothers became interested in the electronic theory of valence to explain how atoms in organic molecules bond together. It was a theory propounded by the physical chemist G. N. Lewis of the University of California at Berkeley. But most organic chemists of the time ignored that theory, if they did not dismiss it outright. Carothers published a paper on the electronic nature of the carbon-carbon double bond in the Journal of the American Chemical Society in 1924. It marked his growing interest in theoretical as well as experimental organic chemistry.

In 1926, Carothers accepted a teaching post in organic chemistry at Harvard University, but he was uncomfortable as a classroom lecturer. When DuPont offered Carothers the opportunity to do fundamental research, at first he was reluctant to accept. He agreed to do so once convinced that he would be free to work on whatever interested him and that he would command an ample budget for supplies and equipment. Stine also provided Carothers with a staff of newly minted Ph.D.s from Colorado, Johns Hopkins, Illinois, MIT, and Michigan. Besides, his $6,000 a year salary would nearly double what Harvard was paying him.

Shortly after arriving at the newly constructed laboratory (later dubbed "Purity Hall") on February 6, 1928, Carothers began to study the structure and synthesis of polymers. He concluded from the literature that long molecules could be strung together from small organic compounds that had a reactive (functional) group at each end. He called these resulting products "condensation polymers" because another compound (such as water) would be split off as a byproduct. Carothers and a small group of young Ph.D. chemists began by reacting dibasic acids (containing two carboxylic acid, -COOH groups) with diols (two alcohol, -OH groups). This reaction, known as esterfication, was roughly akin to linking together a chain of paper clips. The resulting long chain molecules were polyesters.

Progress was rapid, and the resulting polymers theoretically interesting. But their molecular weights were 4,000 or less. Carothers was aiming for larger molecules. He concluded that the water formed during the esterfication reaction was limiting the chain length.

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