Another major category of high performance materials is that of synthetic polymers, commonly known as plastics. Unknown before the 20th century, they are now ubiquitous and immensely varied. The first of the breed was created in 1907 by a Belgium-born chemist named Leo Baekeland. Working in a suburb of New York City, he spent years experimenting with mixtures of phenol (a distillate of coal tar) and formaldehyde (a wood-alcohol distillate). Eventually he discovered that, under controlled heat and pressure, the two liquids would react to yield a thick brownish resin. Further heating of the resin produced a powder, which became a useful varnish if dissolved in alcohol. And if the powder was remelted in a mold, it rapidly hardened and held its shape. Bakelite, as the hard plastic was called, was an excellent electrical insulator. It was tough; it wouldn't burn; it didn't crack or fade; and it was unaffected by most solvents. By the 1920s the translucent, amber-colored plastic was everywhere—in pipe stems and toothbrushes, billiard balls and fountain pens, combs and ashtrays. It was "the material of a thousand purposes," Time magazine said.

Other synthetic polymers soon emerged from research laboratories in the United States and Europe. Polyvinyl chloride, useful for adhesives or in hardened sheets, appeared in 1926. Polystyrene, which yielded very lightweight foams, was introduced in 1930. A few years later came a glass substitute, chemically known as polymethyl methacrylate but sold under the name of Plexiglas.

During this period of plastics pioneering, many chemists were convinced that the new materials were composed of small molecules of the sort familiar to their science. A German researcher named Hermann Staudinger had a very different vision, however. Polymers, he said, were made up of extremely long molecules comprising thousands of subunits linked together in various ways by chemical bonding between carbon atoms. His insight, ultimately honored with a Nobel Prize, won general acceptance by the mid-1930s and gave new momentum to the polymer hunt.