Ziegler, Karl (tsēˈglər) [key], 1898–1973, German chemist. Educated at the Univ. of Marburg, he taught at Heidelberg and Halle and for a short period at the Univ. of Chicago. He became director of the Max Planck Institute for Coal Research at Mülheim an der Ruhr in 1944. He shared the 1963 Nobel Prize in Chemistry with Giulio Natta for developing a system to control polymerizing, or uniting, of simple hydrocarbons into large molecule substances. This had important commercial use in the development of plastics, particularly the polymerization of propene (see polypropylene).