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A Density Functional Study on the Influence of the Molecular Flexibility of Donors on the Insertion Barrier and Stereoselectivity of Ziegler-Natta Propylene Polymerization

✍ Scribed by Toshiaki Taniike; Minoru Terano

Publisher
John Wiley and Sons
Year
2009
Tongue
English
Weight
410 KB
Volume
210
Category
Article
ISSN
1022-1352

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✦ Synopsis

Abstract

The performance of MgCl~2~‐supported Ziegler‐Natta catalysts for propylene polymerization is highly dependent on the molecular structures of donors. Density functional calculations were conducted to examine the molecular behaviors of ethylbenzoate (EB), which coadsorbed with an active Ti species during the propylene insertion. It was found that the degree of the molecular flexibility of EB dominated the catalytic nature of the Ti species. The Ti species with geometrically fixed EB was highly isospecific but poorly active, while that with free EB was active but non‐specific. An appropriate confinement of the flexibility was proposed to be essential for active and isospecific propylene insertion, which might be achieved by steric interference between EB molecules adsorbed close to each other on the MgCl~2~ surface.

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