Karl Ziegler was born in Helsa, Germany, on November 26, 1898. At age eighteen he entered the University of Marburg/Lahn to begin advanced courses in chemistry. In 1920 he received his doctorate in organic chemistry. Following a brief stint at the University of Frankfurt/Main, he became a professor at the University of Heidelberg, where he remained for 10 years. He married Maria Kurz in 1922.
Ziegler became interested in trivalent carbon compounds--carbon molecules with three functional groups. Because these compounds are free radicals with an unbonded electrons, they tend to be highly reactive. Ziegler was specifically interested in carbons with aromatic rings as substituents because they tend to be more stable. He studied the steric and electronic effectsof substituents on reactions, proving through systematic studies that stablefree radicals could be formed even if the ring substituents were not present, and that larger substituents led to more stable free radicals. For the nextthirty years Ziegler and his colleagues studied the effects of functional groups on reactions and the formation of free radicals. Their research showed that organometallic compounds --organic compounds with carbon-metal bonds--are instrumental in forming free radicals.
In 1928, while Professor of Chemistry at the University of Heidelberg, he discovered that by combining an organometallic compound containing potassium with an olefin, he could insert the olefin between the compound and the potassium, thereby lengthening the carbon chain. When an excess of olefin was used, apolymer would result as the addition reaction repeated itself. Ziegler went on to research the formation of carbon rings, succeeding in creating rings that contained up to 30 carbon atoms with very high yields. He was appointed Professor of Chemistry and Director at the University of Halle/Saale in1936. From 1943 until 1969 he was Director of the Max-Planck-Institut fur Kohlenforschung (formerly the Kaiser-Wilhelm-Institut fur Kohlenforschung. In 1953, while doing research at the institute, Ziegler discovered, mostly throughserendipity, a process for generating high-molecular weight polyethylene using metallic catalysts. While trying to obtain it, Ziegler and Heinz Martin, ended up with a dimer--a short-chain polymer composed of two molecules of thesame chemical composition--of ethylene. After some investigation they surmised that the reaction vessel they had used had contained a small amount of nickel. Realizing that other metals could also affect the reaction and inhibit polymerization, they began to investigate. To their surprise they foundthat while some metals were found to inhibit polymerization, others enhancedit. They also found that a metal chloride used with organoaluminum compoundscaused the rapid low-temperature polymerization of ethylene into a very highmolecular weight linear chain. The discovery of catalysts that made possiblelow-temperature polymerization revolutionized the chemical industry.
Karl Ziegler was unique in that he contributed both to theoretical knowledgeand practical industrial chemistry. He shared the Nobel Prize in chemistry in1963 with the Italian chemist Giulio Natta (1903-1979) and went on to research electrolytic processes. He died in 1973 after a short illness.