Recent developments in the polymerization of olefins with organometallic catalysts

Some recent developments in basic research on the polymerization of olefins to linear polymers are reviewed, including progress in preparation of catalytic systems, advances in knowledge about the mechanism of polymerization and attempts to control molecular weight distribution. For the catalytic systems of the type TiCl4/MgCl2/AIR3/Lewis bases indirect methods for the characterization of the active centers are considered. Dissimilarities in the time dependence of the rate of polymerization and changes in the productivity as a function of the Lewis base-to-aluminum alkyl ratio indicate that ethylene and propylene polymerize, at least in a large part, on different active centers. However, productivity of the highly stereospecific centers synthesizing isotactic poly(α-olefin)'s is of the same order of magnitude for ethylene and propylene.