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Regio- and stereospecificity in propene polymerization with MgCl2-supported Ziegler-Natta catalysts: effects of hydrogen and the external donor

✍ Scribed by John C. Chadwick; Gerard M. M. Van Kessel; Olof Sudmeijer

Publisher
John Wiley and Sons
Year
1995
Tongue
English
Weight
335 KB
Volume
196
Category
Article
ISSN
1022-1352

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✦ Synopsis

Investigation of the effects of hydrogen and different external donors on the stereoregularity and chain-end distribution of polypropylene prepared using MgCl,/TiCl,/phthalate ester-AIEt,alkoxysilane catalyst systems has not only confirmed the importance of regiospecificity in relation to hydrogen activation but has also indicated a significant effect of stereospecificity. Alkoxysilanes giving high isospecificity also give high molecular weight polypropylene. Polymer stereoregularity also increases with increasing hydrogen concentration in polymerization. These effects indicate that not only regioirregular but also stereoirregular insertion slows down chain propagation. In each case the probability of chain transfer with hydrogen is higher than that following a stereoregular insertion, and in each case chain transfer with hydrogen leads to the regeneration of isospecific propagation.

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Hydrogen activation in propene polymeriz
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## Abstract ^13^C NMR analysis of poly(propylene) fractions of different tacticity, obtained using a catalyst system of type MgCl~2~/TiCl~4~/diisobutyl phthalate – AlEt~3~ – diether, has provided further evidence that the active species in this system are similar to those in which the ether is used