Polymers have become indispensable in the 21st century, andtoday we cannot imagine life without them. However, tillaround the beginning of the last century, the science of polymerswas considered a very primitive discipline, and majorityof the scientific community did not believe that polymers evenexisted. Hermann Staudinger, among others, fought a longbattle to convince the scientific community that polymers arereal and that they are long chain molecular entities. Buildingon this rational bedrock of polymer science, Prof. KarlZiegler laid the foundation of ethylene polymerization. Asoutlined by Dr. Sivaram in his articles on Ziegler and Natta,careful observations and systematic analyses of serendipitousresults enabled Ziegler to develop the enormously significant

‘M¨ulheim atmospheric polyethylene process’. A decade later,Cossee and Arlman revealed the mechanism of this polymerizationreaction, which is called ‘insertion polymerization’.Insertion polymerization is popularly known as the ‘Ziegler–Natta polymerization’, in recognition of its founding fathers.Today, the world produces about 180 million tons of polyolefinsannually, and polyethylene or polythene has become ahousehold name.

In this article, I shall present an overview of Ziegler–Nattapolymerization. I will highlight the mechanism of this reaction,and outline the progress made in the last seven decadesusing some real-world examples. The last part of this article will take a stock of the unresolved challenges posed byZiegler–Natta polymerization, briefly discuss current solutions,and reiterate the enormous potential of this seventyyear-old reaction to meet contemporary challenges.