Olefin polymerization by (cyclopentadienyl)(ketimide)titanium(IV) complexes of the type, Cp′TiCl2(N=CBu2)-methylaluminoxane (MAO) catalyst systems |
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Authors: | Kotohiro Nomura Kazuya Fujita Michiya Fujiki |
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Affiliation: | Graduate School of Materials Science, Nara Institute of Science and Technology (NAIST), 8916-5 Takayama, Ikoma Nara 630-0101, Japan |
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Abstract: | Effects of substituents on cyclopentadienyl group for homopolymerization of ethylene, 1-hexene, and for ethylene/1-hexene copolymerization using a series of nonbridged (cyclopentadienyl)(ketimide)titanium complexes of the type, Cp′TiCl2(N=CtBu2) [Cp′ = Cp (1), tBuC5H4 (2), C5Me5 (Cp*, 3), and indenyl (4)] have been explored in the presence of methylaluminoxane (MAO) cocatalyst. Complexes 1–3 showed the similar catalytic activities for ethylene polymerization although the activity by 4 was somewhat low, whereas the activity for 1-hexene polymerization increased in the order 1 > 4 2 > 3. These complexes showed significant activities for ethylene/1-hexene copolymerization affording high molecular weight poly(ethylene-co-1-hexene)s with unimodal molecular weight distributions, and the activity increased in the order: 4 > 1 2, 3. The rErH values in the polymerization by 1–3 at 40 °C were 0.35–0.52 which clearly indicate that the 1-hexene incorporation in the copolymerization did not proceed in a random manner. The rE values by 1–3 were 6.0–6.4 and the values were independent upon the cyclopentadienyl fragment employed; the rE values by 4 at 40 °C were 10.2–10.9 which were close to those by ansa-metallocene complex catalysts. These values were influenced by the polymerization temperature, and the 1-hexene incorporation by 1–4 became inefficient at higher temperature, although the observed activities especially by 1, 4 were highly remarkable. |
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Keywords: | Titanium Polymerization Homogeneous catalysis Ethylene Microstructure |
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