Wallace Carothers was 32 years old when he was appointed director of Du Pont Corporation’s research center. He had studied and taught organic chemistry before that, with a specialization in polymers, molecules composed of long chains of repeating units of atoms. Polymers were little-understood molecules when Carothers began his work. He made major contributions to the understanding of their structure and of polymerization, how these long chain molecules form.
Du Pont’s goal was basic research with possible industrial applications, especially in the field of artificial materials. Carothers’ team first investigated the acetylene family of chemicals. He published papers and obtained patents, and in 1931, Du Pont started to manufacture neoprene, a synthetic rubber (commonly used in wetsuits) created by Carothers’ lab.
The search was on for a synthetic fiber. By 1934, Carothers had a promising development: He combined the chemicals amine, hexamethylene diamine, and adipic acid. It created fibers! But they were weak. They had formed by the polymerizing process known as a condensation reaction, in which individual molecules join together, with water as a byproduct. Carothers’ breakthrough came when he realized the water produced by the reaction was dropping back into the mixture and getting in the way of more polymers forming. He adjusted his equipment so that the water was distilled and removed from the system. It worked!
Carothers drew out fibers that were long, strong, and very elastic. Du Pont named this product nylon. The chemists called it Nylon 66 because the adipic acid and hexamethylene diamine each contain 6 carbon atoms per molecule. Each molecule consisted of 100 or more repeating units of carbon, hydrogen, and oxygen atoms, strung in a chain. A filament of nylon may have a million or more molecules, each taking some of the strain when the filament is stretched.
It was exactly what Du Pont had hoped for, and nylon was patented in 1935. It hit the markets in 1939 and was an instant hit, especially as a replacement for silk in hosiery. In fact, before long “nylons” and “stockings” were synonyms in everyday speech. Carothers did not see the widespread application of his work — in consumer goods such as toothbrushes, fishing lines, and lingerie, or in special uses such as surgical thread, parachutes, or pipes — nor the powerful effect it had in launching a whole era of synthetics. He died in April, 1937.