Polymerization of propylene catalyzed by α-diimine nickel complexes/methylaluminoxane: catalytic behavior and polymer properties (original) (raw)
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Polymerization of ethylene with nickel α-diimine catalysts
Macromolecular Rapid Communications, 1997
Br or CH3) were tested in ethylene polymerization after activation with different co-catalysts, such as methylaluminoxane, AI(C2H5)zCl or other aluminium alkyls, and ionizing reagents like B(C&)3, [CPh3][B(C6F5)4] or HBF,. The performances of the different catalytic systems were compared with reference to polymer productivity and structure. The degree of branching of the obtained polyethylenes was shown to depend not only on the ligand environment at the Ni centre but also on the type of co-catalyst.
Polymer, 2004
Ethylene polymerization was carried out using three nickel a-diimine catalysts ((ArNaC(An)-C(An)aNAr)NiBr 2 (1), (ArNaC(CH 3)-C(CH 3)aNAr)NiBr 2 (2) and (ArNaC(H)-C(H)aNAr)NiBr 2 (3); where AnZacenaphthene and ArZ2,6-(i-Pr) 2 C 6 H 3) activated with modified methylaluminoxane (MMAO) in a slurry semi-batch reactor. We investigated the effects of ethylene pressure, reaction temperature, and a-diimine backbone structure variation on the catalyst activity and polymer properties. Changes in the a-diimine backbone structure had remarkable effect on the polymer microstructure as well as the catalyst activity. Catalyst 2 produced polymer with the highest molecular weight, while Catalyst 3 produced polymer with the lowest molecular weight. In addition, Catalyst 2 produced polymer with the lowest melting point, while Catalyst 3 produced the highest melting level exhibiting a melting behavior typical of high-density polyethylene (HDPE). With all the three catalysts, polymer molecular weight tended to decrease with increasing polymerization temperature due to the increase in chain transfer rates. In general, there was no clear and consistent trend observed for the effects of ethylene pressure on the polymer molecular weight. However, in polyethylene produced with Catalyst 2, the molecular weight was independent of ethylene pressure suggesting that chain transfer to ethylene may be a dominant mechanism for this catalyst.
Highly active new α-diimine nickel catalyst for the polymerization of α-olefins
Journal of Organometallic Chemistry, 2005
A new silylated a-diimine ligand, bis[N,N 0 -(4-tert-butyl-diphenylsilyl-2,6-diisopropylphenyl)imino]acenaphthene 3, and its corresponding Ni(II) complex, {bis[N,N 0 -(4-tert-butyl-diphenylsilyl-2,6-diisopropylphenyl)imino]acenaphthene}dibromonickel 4, have been synthesized and characterized. The crystal structures of 3 and 4 were determined by X-ray crystallography. In the solid state, complex 4 is a dimer with two bridging Br ligands linking the two nickel centers, which have square pyramidal geometries. Complex 4, activated either by diethylaluminum chloride (DEAC) or methylaluminoxane (MAO) produces very active catalyst systems for the polymerization of ethylene and moderately active for the polymerization of propylene. The activity values are in the order of magnitude of 10 7 g PE (mol Ni [E] h) À1 for the polymerization of ethylene and of 10 5 g PP (mol Ni [P] h) À1 for the polymerization of propylene. NMR analysis shows that branched polyethylenes (PE) are obtained at room or higher temperatures and almost linear PE is obtained at 0°C with 4/DEAC.
Propylene polymerization with nickel-diimine complexes containing pseudohalides
Journal of Polymer Science Part A: Polymer Chemistry, 2006
DADNiX 2 nickel-diimine complexes [DAD ¼ 2,6-iPr 2 À ÀC 6 H 3 À ÀN¼ ¼C(Me)À À C(Me)¼ ¼NÀ À2,6-iPr 2 À ÀC 6 H 3 ] containing nonchelating pseudohalide ligands [X ¼ isothiocyanate (NCS) for complex 1 and isoselenocyanate (NCSe) for complex 2] were synthesized, and the propylene polymerization with these complexes and also with the Br ligand (X ¼ Br for complex 3) activated by methylaluminoxane (MAO) were investigated (systems 1, 2, and 3/MAO). The polypropylenes obtained with systems 1, 2, and 3 were amorphous polymers and had high molecular weights and narrow molecular weight distributions. Catalyst system 1 showed a relatively high activity even at a low Al/Ni ratio and reached the maximum activity at the molar ratio of Al/Ni ¼ 500, unlike system 3. Increases in the reaction temperature and propylene pressure favored an increase in the catalytic activity. The spectra of polypropylenes looked like those of propylene-ethylene copolymers containing syndiotactic propylene and ethylene sequences. At the same temperature and pressure, system 2 presented the highest number of propylene sequences, and system 3 presented the lowest. V V C 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 458-466, 2006
Polymer Engineering & Science, 2010
This article regards the ethylene polymerization catalyzed by a nickel catalyst and activated by ethylaluminum sesquichloride (EASC). The effects of the reaction conditions [polymerization temperature, cocatalyst (EASC) concentration, and ethylene concentration] on the average molecular weights of the final polymers and reaction yields were evaluated with the help of empirical statistical models. It is shown that reaction temperature and cocatalyst (EASC) concentration exert the most important effects on average molecular weights and catalyst activity. The polydispersities of the obtained polyethylenes are larger than the polydispersities of polyethylenes obtained with typical Brookhart catalysts. The analysis of polymer branching frequencies shows new types of short branching and significant amounts of long branches, which may explain the relatively large polydispersities of the obtained polymer samples.
Polymer Bulletin, 2017
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2000
This article deals with the ethylene polymerization with nickel catalyst activated by ethyl- aluminum sesquichloride (EASC). The effects of the reaction conditions (polymerization temperature, co- catalyst (EASC) concentration, ethylene concentration) on the polymer molecular weight distribution and the reaction yield were evaluated using empirical models. The temperature and the co-catalyst (EASC) concentration showed the largest effect on polymer molecular weight
Polymerization of styrene with nickel complex/methylaluminoxane catalytic systems
Journal of Polymer Science Part A: Polymer Chemistry, 1998
Polymerization of styrene using catalytic systems based on nickel derivatives and methylaluminoxane (MAO) was studied. Among tested catalysts, nickel bis-(acetylacetonate) and nickel dichloride show the maximum activity. Bis(phosphine)nickel dichlorides exhibit lower activity, depending on the nature of the phosphine ligand. Polymer yields decrease by lowering the catalyst concentration, by increasing the reaction temperature, or by carrying out the polymerization in a polar donor solvent. Weight average molecular weight of most of the prepared polystyrenes ranges from 9000 to 25,000, with polydispersity indexes of 1.6-3.8. However, polystyrene prepared in dioxane solvent exhibits a small fraction of very high molecular weight (about 140,000). From NMR analysis, the products seem generally to be constituted of two polymers with different steric microstructure: atactic polystyrene and partially isotactic polystyrene (ca. 75-85% meso diads). Catalytic site specificity is correlated with the type of nickel ligand, while the effect of reaction temperature is less defined. ᭧ 1998
Journal of Polymer Research, 2012
Ethylene (E), propylene (P), and 1-pentene (A) terpolymers differing in monomer composition ratio were produced, using the metallocenes rac-ethylene bis(indenyl) zirconium dichloride/methylaluminoxane (rac-Et(Ind) 2 ZrCl 2 /MAO), isopropyl bis(cyclopentadienyl)fluorenyl zirconium dichloride/methylaluminoxane (Me 2 C(Cp)(Flu)ZrCl 2 /MAO, and bis(cyclopentadienyl)zirconium dichloride, supported on silica impregnated with MAO (Cp 2 ZrCl 2 /MAO/SiO 2 /MAO) as catalytic systems. The catalytic activities at 25 8C and normal pressure were compared. The best result was obtained with the first catalyst. A detailed study of 13 C NMR chemical shifts, triad sequences distributions, monomer-average sequence lengths, and reactivity ratios for the terpolymers is presented. V V C 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 947-957, 2008