ISSN:
0887-624X
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Bis(arene) complexes of zerovalent titanium, zirconium, and hafnium supported on partially dehydroxylated, fumed alumina are effective catalysts for the polymerization of olefins. The zerovalent complexes react with surface hydroxyls with loss of one equivalent of arene to yield the active species. The polyethylenes derived from these catalysts are very high molecular weight. Polymerization of propylene yields elastomeric stereoblock polymers which are composed of isotactic and stereoirregular sequences. The polymers are stiffer than polypropylenes obtained with similar catalysts derived from tetra(neophyl)zirconium. The chain microstructures of the various components of the whole polymers have been characterized by 13C-NMR and solvent extraction studies. The ether soluble component of these polymers is of a relatively high molecular weight and the microstructure of the backbone is largely stereoirregular. It is the cocrystallization of this fraction of the polymer with the crystalline, isotactic fractions which is critical to the observed elastomeric properties.
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pola.1989.080270916
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