Investigating organometallic compounds using the tri-methylaluminium compound, Ziegler had unexpected results. Tracking this down to nickel impurities, he experimented with many alkylaluminium compounds. Titanium compounds led to the production of long, unbranched, polymer chains.
In the search for understanding and control of Ziegler-Natta polymerization at the molecular level, a number of metallocene catalysts have been developed, often offering fine control over the composition and tacticity of the polymer chain so produced.