Modification of the Bridge and Syndiotactic Polymer Molecular Weight

1 Modification of the Bridge and Syndiotactic Polymer Molecular Weight 

Based on a series of molecular mechanic calculations and polymerization experiments performed with a number of ania-bis-(fluorenyl)zirconium dichloride complexes, Alt et al. [109-112] demonstrated that the size of the bridging unit plays an important role in the final catalytic activity of these complexes towards ethylene polymerization. A bigger bite angle, i.e., bigger opening around the active site, is supposed to increase the catalytic activity because of a less-hindered monomer 

10 Top view of the molecular structure of complex (q -CsELi-p-Et-q -C,3H8)ZrCl2, 5 

Little was known about the influence of the bridge and bridge substituent(s) on the catalytic performance with respect to the molecular weight of the resulting polymer until the advent of the syndiotactic-selective metallocene catalyst systems. The following two sections describe the modifications of the size and substituents of the inter-annular bridge in complex 1 and their impact on the catalytic performance and resulting s-PP. 

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