Mechanism Of Stereospecific Polymerization Research Articles

Active Sites Structure and Mechanism of Stereospecific Polymerization of α-Olefins and Dienes Employing Ziegler-Natta Catalysts

Abstract Stereospecific polymerization of α-olefin and diene hydrocarbons in the presence of catalysts of a new type proposed by Ziegler and Natta is a significant discovery of the twentieth century in the chemistry of macromolecular compounds. Heterogeneous Ziegler-Natta catalysts involving Ti and V trichlorides in combination with organoaluminum compounds have been widely used for nearly 30 years in commercial stereospecific polymerization of a number of o-olefins (propylene, hexene-l,4-methyl-pentene-1, etc.) and dienes (butadiene, isoprene, etc.). However, despite the great success achieved in practical implementation of the processes there is no common point of view so far and broad discussions are still under way as to the mechanism of polymerization and stereoregulation in the presence of the above catalysts.

Polymerization Mechanism in Methyl Methacrylate–Grignard Reagent System. I. Phenylmagnesium Bromide

The mechanism of stereospecific polymerization in a methyl methacrylate–Grignard reagent (C6H5MgBr) system is studied as a function of polymerization temperature with high-resolution nuclear magnetic resonance (NMR) spectroscopy for obtained polymers. It is found that the maximum temperature during the reaction in our experiments is appropriate for adoption as the polymerization temperature rather than the commonly used setting temperature.As a result it is found that the mechanism is different at temperatures higher and lower than about 266°K. Also, the NMR spectra of C6H5MgBr in a deuterated toluene-d8 are measured over a wide range of temperatures and remarkable change is observed in the vicinity of about 266°K. It may reflect the above difference in polymerization mechanisms on both sides of about 266°K.

Stereoregular polymers and polymerization

The historical development is traced of processes leading to the stereoregular polymerization of various substances with a view to indicating lines of interest for further exploratory work. Principal subdivisions of the text include: types of steric arrangements experimentally obtained, general considerations on the mechanism of stereospecific polymerization, some properties of stereoregular polymers, and future developments and applications.

Mechanism of stereospecific polymerization

Mechanism of stereospecific polymerization