Karl Ziegler & Giulio Natta

The year 1953 could hardly sit still. Stalin died in March; in April, Watson and Crick unveiled the double helix; in May, Hillary and Norgay stood atop Everest; in June, a young queen was crowned in Westminster Abbey while the world watched on flickering television sets; in July, the guns of Korea finally fell silent. And in the coal-country town of Mülheim an der Ruhr, in a laboratory officially devoted to coal research, a German chemist ran an experiment that would put more plastic into the everyday world than perhaps any other single discovery: ethylene, polymerizing briskly into long, orderly chains, at ordinary pressure, in ordinary glassware.

The Aufbau Master of Mülheim

Karl Ziegler, born in 1898 in the village of Helsa near Kassel, was the sort of student who made universities feel slow; he skipped early coursework at Marburg and had his doctorate by 1920, at twenty-one. He built his reputation on the exotic frontier of organometallic chemistry: stabilized radicals, lithium alkyls, and eventually the “Aufbau” (growth) reaction, in which organoaluminum compounds stitched ethylene units one by one onto a growing chain. In 1943 he became director of the Kaiser Wilhelm (later Max Planck) Institute for Coal Research in Mülheim, where he enjoyed a freedom rare in industrial Germany: the freedom to follow the chemistry wherever it wandered.

In 1953 it wandered somewhere remarkable, by way of a mishap. A polymerization run produced not the expected long chains but a flood of useless 1-butene, and the culprit turned out to be a trace of nickel lingering in the equipment. Where others might have scrubbed the reactor and moved on, Ziegler saw the deeper message: if an accidental trace of one metal could redirect the whole reaction, a deliberately chosen metal might supercharge it. His team hunted through the periodic table, and with his student Heinz Breil found the answer in titanium. Titanium salts plus aluminum alkyls polymerized ethylene at atmospheric pressure into high-molecular-weight, beautifully linear polyethylene, with no thousand-atmosphere reactors, no tangle of branches. The age of high-density polyethylene had begun in a modest German flask.

The Architect of Order in Milan

Giulio Natta, born in 1903 in the Ligurian coastal town of Imperia, was Ziegler’s temperamental opposite: where Ziegler was a maestro of reactive metal compounds, Natta was a structuralist, a chemical engineer (Politecnico di Milano, class of 1924) who had mastered X-ray and electron diffraction, the art of seeing how molecules pack. In the early 1930s he had already broken a German industrial monopoly by developing a methanol synthesis process with the Italian chemical giant Montecatini. By 1938 he headed chemical engineering at his alma mater in Milan, with Montecatini as his industrial partner.

In 1952, Ziegler disclosed his organometallic work to Montecatini, where Natta was a consultant, and Natta immediately saw what the new catalysts might do for molecular architecture. His target was propylene, ethylene’s unrulier sibling, whose dangling methyl groups had always produced sticky, amorphous messes. On March 11, 1954, Natta’s group in Milan produced isotactic polypropylene: every methyl group marching down the same side of the chain, a crystalline, tough, gloriously useful plastic. Where Ziegler’s catalysts had made polymer chains long and straight, Natta’s work made them stereoregular, introducing an entirely new dimension of control that chemists now call tacticity.

Two Labs, One Revolution

The two men’s contributions interlock so tightly that this Atlas gives them a single page, just as Stockholm gave them a single prize. Ziegler supplied the catalytic engine; Natta supplied the stereochemical steering wheel and the X-ray evidence to prove it. By 1956, Ziegler–Natta catalysts were in commercial polyolefin production, and the world began filling up with the results: HDPE pipes and jerrycans, polypropylene chairs, ropes, carpets, car bumpers, and the humble bottle cap. That is billions of tonnes of the most-produced plastics on Earth, all descended from that contaminated Mülheim reactor.

In 1963 the pair shared the Nobel Prize in Chemistry. For Natta the podium came at a cruel price: Parkinson’s disease, diagnosed in 1956, had advanced so far that he needed assistance to deliver his Nobel address. Ziegler, whose patent agreements had made him genuinely wealthy, poured some 40 million deutsche marks back into his institute’s research and, with his wife Maria, assembled a splendid collection of German Expressionist paintings (Nolde, Heckel, Kokoschka) later bequeathed to a Mülheim museum. Ziegler died in 1973; Natta followed in 1979. Their catalysts, refined through five generations and still evolving, remain the workhorses of the polyolefin industry. This is chemistry’s finest reminder that a “failed” experiment is sometimes the most valuable kind.