How it began
Giulio Natta and his coworkers in Milan obtained polypropylene with a regular structure on March 11, 1954. It was the first polymer to show that stereospecific polymerization catalysts existed. Natta worked closely with the Italian chemical company Montecatini, which registered the first patent on isotactic polypropylene in Italy on June 8, 1954, in the names of Natta, Piero Pino and Giorgio Mazzanti.
Before it existed
The discovery had its roots in the work of Karl Ziegler in Germany on the polymerization of ethylene with a titanium compound. Natta saw that the metal chloride acted as a catalytic activator and reasoned that the same activation should apply to propylene and other olefins. In the early 1950s large molecules with very regular structures, such as cellulose and some natural rubbers, were known, but nobody knew how to make such regularity synthetically.
How it works
In the isotactic polymer, identical propylene units join head to tail in a very regular chain, with the methyl groups all on the same side. Natta's group also described syndiotactic chains, in which the groups alternate from side to side, and atactic chains with no regular order. The regular chains form crystals, which the team observed under the microscope and by X-ray diffraction.
What lasted
The isotactic polymer was soon recognized to have much better properties than the atactic form, especially mechanical ones. Montecatini produced it under the trade name Moplen, and by the 1960s it was being molded into shiny plastic household goods. The discovery proved revolutionary for the chemical industry worldwide and focused research on catalysts that place atoms precisely in space. Natta and Ziegler shared the Nobel Prize in 1963. Montecatini became Montedison in 1970.
