Coordination Polymerization

In the early 1950's a major new polymerization tecnique was dissolved that led to the production of polymers with unusual stereospecific structures. Although there were earlier indications of this type of polymerization, the field actually came into existence with the work of Ziegler (1955) and Natta (1955), who developed new polymerization catalyst with unique stereoregulating powers. Their Nobel Prize addresses (Ziegler 1964, Natta 1965) form excellent introductions to the field.

Since the earliest days, a number of names have been applied to the polymerization technique using what have become known as Ziegler or Ziegler Natta catalyst. Some have emphasized the stereoregulating features of certain of these polymerization, but that is not an essential feature. The term polyinsertion is still used, suggestive of chain propagation by the insertion of a monomer between the catalyst and the polymer chain to which it is attached, but the term coordination polymerization, used early to suggest the essential feature of a coordination complex with the catalyst, has remained and has been justified by mechanistic studies.

Coordination polymerization is far from simple in term of mechanism, kinetics, or application. The most important catalyst systems are known. Additional complications to the study of coordination systems arise because the same catalysts, under other conditions, can initiate polymerization by cationic, anionic, or even free radical mechanisms. One often coordination polymerization is carried out using a catalyst in the form of a slurry of small solid particles in an inert medium or a supported solid catalyst. Heterogeneous polymerization is not essential for coordination and the development of stereospecificity, however, for sufficient polar monomers.