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Modified Methylaluminoxane (modified + methylaluminoxane)
Selected AbstractsPreparation of linear ,-olefins to high-molecular weight polyethylenes using cationic ,-diimine nickel(II) complexes containing chloro-substituted ligands,JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2006Chun-Lei Song Abstract A series of ,-diimine nickel(II) complexes containing chloro-substituted ligands, [(Ar)NC(C10H6)CN(Ar)]NiBr2 (4a, Ar = 2,3-C6H3Cl2; 4b, Ar = 2,4-C6H3Cl2; 4c, Ar = 2,5-C6H3Cl2; 4d, Ar = 2,6-C6H3Cl2; 4e, Ar = 2,4,6-C6H2Cl3) and [(Ar)NC(C10H6)CN(Ar)]2NiBr2 (5a, Ar = 2,3-C6H3Cl2; 5b, Ar = 2,4-C6H3Cl2; 5c, Ar = 2,5-C6H3Cl2), have been synthesized and investigated as precatalysts for ethylene polymerization. In the presence of modified methylaluminoxane (MMAO) as a cocatalyst, these complexes are highly effective catalysts for the oligomerization or polymerization of ethylene under mild conditions. The catalyst activity and the properties of the products were strongly affected by the aryl-substituents of the ligands used. Depending on the catalyst structure, it is possible to obtain the products ranging from linear ,-olefins to high-molecular weight polyethylenes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1964,1974, 2006 [source] Ethylene/,-olefin copolymerization with bis(,-enaminoketonato) titanium complexes activated with modified methylaluminoxaneJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2005Li-Ming Tang Abstract Copolymerizations of ethylene with ,-olefins (i.e., 1-hexene, 1-octene, allylbenzene, and 4-phenyl-1-butene) using the bis(,-enaminoketonato) titanium complexes [(Ph)NC(R2)CHC(R1)O]2TiCl2 (1a: R1 = CF3, R2 = CH3; 1b: R1 = Ph, R2 = CF3; and 1c: R1 = t -Bu, R2 = CF3), activated with modified methylaluminoxane as a cocatalyst, have been investigated. The catalyst activity, comonomer incorporation, and molecular weight, and molecular weight distribution of the polymers produced can be controlled over a wide range by the variation of the catalyst structure, ,-olefin, and reaction parameters such as the comonomer feed concentration. The substituents R1 and R2 of the ligands affect considerably both the catalyst activity and comonomer incorporation. Precatalyst 1a exhibits high catalytic activity and produces high-molecular-weight copolymers with high ,-olefin insertion. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6323,6330, 2005 [source] Effect of Solvents on Living Polymerization of Propylene with [t -BuNSiMe2Flu]TiMe2 -MMAO Catalyst SystemMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 3 2004Kei Nishii Abstract Summary: Batchwise polymerization of propylene was conducted at 0,°C in heptane using [tert -BuNSiMe2Flu]TiMe2 (1) combined with dried methylaluminoxane (MAO) and dried modified methylaluminoxane (MMAO), which were prepared from the toluene solutions of MAO and MMAO by removing the solvent and the free trialkylaluminium. The dried MMAO system quantitatively gave the polymer with higher molecular weight and narrower molecular weight distribution (MWD), ca. 1.3, compared with the dried MAO system. In addition, the polymerization with dried MMAO in toluene, chlorobenzene (CB) and ortho -dichlorobenzene (o -DCB), as solvent, also produced polymers quantitatively with MWD of ca. 1.1,1.3. The number-average molecular weight () of the polymers, obtained with these systems, increased linearly against the polymer yield, while the narrow MWD was retained and the number of polymer chains was almost constant. The results of post-polymerization in heptane and o -DCB proved that the living polymerization proceeded irrespective of the solvent used. The semi-batch polymerizations under an atmospheric pressure of propylene indicated that the propagation rate was more than 10 times higher in o -DCB than in heptane. The 13C NMR analysis of the polymers indicated that the syndiotacticity also depended on the polarity of the solvent and increased in the following order: CB,,,o -DCB,<,toluene,<,heptane. A plausible scheme for the interaction between active species and solvents. [source] A Novel Synthetic Procedure for Stereoblock Poly(propylene) with a Living Polymerization System,MACROMOLECULAR RAPID COMMUNICATIONS, Issue 10 2004Kei Nishii Abstract Summary: Propylene polymerization was conducted at 0,°C in heptane or chlorobenzene (CB) by an ansa -fluorenylamidodimethyltitanium complex combined with dried, modified methylaluminoxane that had been treated by dilution with heptane and successively repeatedly vacuum dried to remove any free trialkylaluminiums. The post-polymerizations testified that the living polymerization proceeded irrespective of the solvent used. The heptane system gave the syndiotactic poly(propylene)s (PPs), whereas the CB system gave almost atactic PPs. After the first polymerization in heptane had been completed, the same amounts of propylene and CB were added for the second polymerization. This procedure gave the syndiotactic-atactic stereoblock PP with narrow molecular-weight distributions. Structure of the ansa -fluorenylamidodimethyltitanium complex and its application to the synthesis of syndiotactic-atactic stereoblock poly(propylene)s reported here. [source] Synthesis, structure and ethylene polymerization of group 4 complexes with phosphinoamide ligandsAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 2 2006Changhe Qi Abstract Group 4 complexes containing diphosphinoamide ligands [Ph2PNR]2MCl2 (3: R = tBu, M = Ti; 4: R = tBu, M = Zr; 5: R = Ph, M = Ti; 6: R = Ph, M = Zr) were prepared by the reaction of MCl4 (M = Ti; Zr) with the corresponding lithium phosphinoamides in ether or THF. The structure of [Ph2PNtBu]2TiCl2 (3) was determined by X-ray crystallography. The phosphinoamides functioned as ,2 -coordination ligands in the solid state and the TiN bond length suggests it is a simple single bond. In the presence of modified methylaluminoxane or i -Bu3Al/Ph3BC(C6F5)4, catalytic activity of up to 59.5 kg PE/mol cat h bar was observed. Copyright © 2005 John Wiley & Sons, Ltd. 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