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Propene polymerization with catalyst mixtures containing different ansa-zirconocenes : chain transfer to alkylaluminum cocatalysts and formation of stereoblock polymers

Propene polymerization with catalyst mixtures containing different ansa-zirconocenes : chain transfer to alkylaluminum cocatalysts and formation of stereoblock polymers

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LIEBER, Susanna, Hans-Herbert BRINTZINGER, 2000. Propene polymerization with catalyst mixtures containing different ansa-zirconocenes : chain transfer to alkylaluminum cocatalysts and formation of stereoblock polymers. In: Macromolecules. 33(25), pp. 9192-9199. ISSN 0024-9297. eISSN 1520-5835. Available under: doi: 10.1021/ma000691j

@article{Lieber2000Prope-23734, title={Propene polymerization with catalyst mixtures containing different ansa-zirconocenes : chain transfer to alkylaluminum cocatalysts and formation of stereoblock polymers}, year={2000}, doi={10.1021/ma000691j}, number={25}, volume={33}, issn={0024-9297}, journal={Macromolecules}, pages={9192--9199}, author={Lieber, Susanna and Brintzinger, Hans-Herbert} }

Lieber, Susanna Propene polymerization with catalyst mixtures containing different ansa-zirconocenes : chain transfer to alkylaluminum cocatalysts and formation of stereoblock polymers terms-of-use eng 2013-06-24T17:06:05Z Brintzinger, Hans-Herbert 2013-06-24T17:06:05Z Lieber, Susanna Macromolecules ; 33 (2000), 25. - S. 9192-9199 2000 Substantial transfer of growing polypropyl chains to methylalumoxane and trimethylaluminum occurs with the highly substituted, isospecific zirconocene catalyst Me<sub>2</sub>Si(2-Me-4-<sup>t</sup>Bu-C<sub>5</sub>H<sub>2</sub>)<sub>2</sub>ZrCl<sub>2</sub>/MAO, while little if any such chain transfer is observed for the more open isospecific catalyst Me<sub>2</sub>Si(2-MeInd)<sub>2</sub>ZrCl<sub>2</sub>/MAO, for aspecific H<sub>4</sub>C<sub>2</sub>(Flu)<sub>2</sub>ZrCl<sub>2</sub>/MAO, and for syndiospecific Ph<sub>2</sub>C(Cp)FluZrCl<sub>2</sub>/MAO. Propene polymerization with MAO-activated mixtures of Me<sub>2</sub>Si(2-MeInd)<sub>2</sub>ZrCl<sub>2</sub> and H<sub>4</sub>C<sub>2</sub>(Flu)<sub>2</sub>ZrCl<sub>2</sub> gives completely separable mixtures of the isotactic and atactic polymers characteristic for each of the individual catalysts. MAO-activated mixtures of Me<sub>2</sub>Si(2-Me-4-<sup>t</sup>Bu-C<sub>5</sub>H<sub>2</sub>)<sub>2</sub>ZrCl<sub>2</sub> and H<sub>4</sub>C<sub>2</sub>(Flu)<sub>2</sub>ZrCl<sub>2</sub>, however, give polypropene mixtures that contain, besides isotactic and atactic polymers, polymer fractions in which isotactic and atactic polypropene chain segments are inseparably linked. While clear evidence for isotactic−syndiotactic stereoblock formation was not obtained, some polymeryl exchange between isospecific and syndiospecific catalyst sites in MAO-activated mixtures of Me<sub>2</sub>Si(2-Me-4-<sup>t</sup>Bu-C<sub>5</sub>H<sub>2</sub>)<sub>2</sub>ZrCl<sub>2</sub> and Ph<sub>2</sub>C(Cp)FluZrCl<sub>2</sub> is indicated by increased stereoerror frequencies in some fractions of the polymer product mixture obtained by temperature-rising elution fractionation. Structural prerequisites for an efficient transfer of growing polymer chains between different types of catalyst centers are discussed. Brintzinger, Hans-Herbert

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