Tantalum- and titanium-based catalytic systems for the synthesis of hyperbranched polyethene
Journal Article
·
· Journal of the American Chemical Society
Hyperbranched polyethene was synthesized using a novel TaCl{sub 5}/alkylaluminum halide catalyst system. The polymers were viscous oils with a ratio of methyl hydrogens/total alkyl hydrogens of 0.25--0.40 and weight-average molecular weights of 600--4,000 daltons. Both branching and molecular weight can be varied by changing reaction conditions and catalyst composition. the system can also be modified to synthesize 1-alkenes (principally, 1-hexene). A second system, involving TiCl{sub 4}/alkylaluminum halide, also gave hyperbranched polyethene, with a ratio of methyl hydrogens/total alkyl hydrogens of 0.10--0.25. Weight-average molecular weights varied from 900 to 1,800 daltons. Higher selectivity to liquid product was achieved through the addition of dihydrogen. The mechanism of the formation of branched polyethene appears to involve, for the most part, oligomerization of ethene to 1-alkenes (principally 1-hexene) by a transition metal alkyl species followed by cationic oligomerization of the 1-alkenes by Lewis acidic species. The addition of tetraalkylammonium chloride to the TaCl{sub 5}/Et{sub 3}Al system resulted in a change in product selectivity from all polyethene to .65% 1-hexene. The highly selective trimerization of ethene by the tantalum system is unusual.
- Research Organization:
- Pennsylvania State Univ., University Park, PA (US)
- Sponsoring Organization:
- US Department of Energy
- DOE Contract Number:
- FG02-84ER13295
- OSTI ID:
- 20017368
- Journal Information:
- Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 9 Vol. 122; ISSN JACSAT; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
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