Homopolymerization stereoregularity

Polymers account for about 3—4% of the total butylene consumption and about 30% of nonfuels use. Homopolymerization of butylene isomers is relatively unimportant commercially. Only stereoregular poly(l-butene) [9003-29-6] and a small volume of polyisobutylene [25038-49-7] are produced in this manner. High molecular weight polyisobutylenes have found limited use because they cannot be vulcanized. To overcome this deficiency a butyl mbber copolymer of isobutylene with isoprene has been developed. Low molecular weight viscous Hquid polymers of isobutylene are not manufactured because of the high price of purified isobutylene. Copolymerization from relatively inexpensive refinery butane—butylene fractions containing all the butylene isomers yields a range of viscous polymers that satisfy most commercial needs (see Olefin polymers Elastomers, synthetic-butylrubber). 

This paper is concerned with some of our experiments in this field. Our purpose was to obtain polymers with extremely high stereoregularity. In the first part we will report on the homopolymerization of butadiene with f-transition metal catalysts. 

Keywords metallocene catalyst, Ziegler-Natta catalyst, olefin polymerization, polyolefins, homogeneous catalysts, supported catalysts, stereoregularity, molecular weight distribution (MWD), chemical composition distribution, Unipol , Novolen , stereoselectivity, single site catalyst, multiple site catalyst, gas phase process, slurry process, homopolymerization, copolymerization. 

In nearly every polymerization system the influence of the solvent on the course of the reaction is important. Thus chain transfer reactions with active chain ends occur in radical polymerization. The solvent can also influence the stereoregularity of the product in anionic polymerizations. The boiling range of the solvents should correspond to that of the monomers and to the decomposition temperature of the initiators. Thus common polymerization temperatures are often between 60 and 120 °C (under reflux of the solvent). A general procedure for the radical homopolymerization of acrylates in solution is given in Ref [35]. 

However, the examination of the steric defects alone in the homopolymerization cannot be considered as fully demonstrative. In fact, it is difficult to deduce probative data on the stereospecific polymerization by examining just those units that are inserted in the chain in a disordered way. In order to obviate this difficulty we started research on stereoregular copolymers of propylene with a low amount of 60% enriched 1 ethylene. 

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