Ethylene polymerization and copolymerization with 10-undecen-1-ol using the catalyst system DADNi(NCS)2/MAO (original) (raw)
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Journal of Polymer Science Part A-polymer Chemistry, 2008
The catalyst DADNi(NCS) 2 (DAD ¼ (ArN¼ ¼C(Me)À ÀC(Me)¼ ¼ArN); Ar ¼ 2,6-C 6 H 3 ), activated by methylaluminoxane, was tested in ethylene polymerization at temperatures above 25 8C and variable Al/Ni ratio. The system was shown to be active even at 80 8C and when supported on silica. However, catalyst activity decreased. The catalyst system was also tested in ethylene and 10-undecen-1-ol copolymerization at different ethylene pressures. The best activities were obtained at low polar monomer concentration (0.017 mol/L), using triisopropylaluminum (Al-i-Pr 3 ) to protect the polar monomer. The incorporation of the comonomer increased with the increase of polar monomer concentration. According to 13 C NMR analyses, all the resulting polyethylenes were highly branched and the polar monomer incorporation decreased as ethylene pressure increased. V V C 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5199-5208, 2007
Journal of Molecular Catalysis A: Chemical, 2003
The combination of the neutral compound (η 3 :η 0 -Ind(CH 2 ) 2 NMe 2 )Ni(PPh 3 )Cl (1) and methylaluminoxane (MAO) produces catalysts for the dimerization and the polymerization of ethylene. On the other hand, activation of the cationic complex [(η 3 :η 1 -Ind(CH 2 ) 2 NMe 2 )Ni(PPh 3 )][BPh 4 ] (2) by MAO or trimethylaluminum leads to a system which dimerizes ethylene with high turnover frequencies (2 × 10 3 s −1 ), but does not promote its polymerization. The effects of parameters such as ethylene pressure, reaction temperature and time, solvent type, and the type and amount of activator used have been studied in order to optimize the conditions for the formation of polyethylene. In addition, a number of reactions have been studied by NMR and GC-MS analysis in an effort to identify the catalytically active species. The results of these studies point to the involvement of cationic species in the dimerization of ethylene, whereas, the active catalyst for the polymerization of ethylene appears to be a non-cationic species.
Journal of the Brazilian Chemical Society, 2005
Blendas de polietileno ramificado/polietileno de alta densidade (BPE/HDPE) foram preparadas usando uma combinação de catalisadores [NiCl 2 (diimina-α)] (1) (diimina-α = 1,4-bis(2,6diisopropilfenila)-acenafeteno) e [Tp Ms* VCl 2 (N t Bu)] (2) (Tp Ms* = hidridobis(3-mesitilapirazol-1il)(5-mesitilapirazol-1-il)). As reações de polimerização foram realizadas em hexano ou tolueno em três diferentes temperaturas (0, 30 e 50 °C), utilizando várias razões molares de níquel (x Ni), na presença de metilaluminoxano (MAO) como cocatalisador. Em todas as temperaturas, as atividades mostraram uma correlação aproximadamente linear com x Ni , indicando o não aparecimento de um efeito sinérgico entre as espécies de níquel e vanádio. Altas atividades foram obtidas a 0 °C. As temperaturas de fusão (T m) das blendas de polietileno produzidas a 0 °C diminuem conforme a x Ni aumenta no meio reacional, indicando uma boa miscibilidade entre as fases de polietileno produzidas por ambos catalisadores. A morfologia da superfície das blendas de BPE/HDPE estudadas por microscopia eletrônica de varredura (MEV) revelou uma baixa miscibilidade entre as fases de PE, principalmente no caso das blendas poliméricas produzidas a alta temperatura (50 ºC). Branched polyethylene/high-density polyethylene blends (BPE/HDPE) were prepared using the combined [NiCl 2 (α-diimine)] (1) (α-diimine = 1,4-bis(2,6-diisopropylphenyl)acenaphthenediimine) and [Tp Ms* VCl 2 (N t Bu)] (2) (Tp Ms* = hydridobis(3-mesitylpyrazol-1-yl)(5mesitylpyrazol-1-yl)) catalysts. The polymerization reactions were performed in hexane or toluene at three different polymerization temperatures (0, 30 and 50 °C) and several nickel molar fractions (x Ni), using MAO as cocatalyst. At all temperatures, the activities show an approximate linear correlation with x Ni , indicating a non-synergistic effect between the nickel and the vanadium species. Higher activities were found in toluene at 0 °C. The melting temperatures for the polyethylene blends produced at 0 °C decrease as x Ni increases in the medium indicating good miscibility between the polyethylene phases made by both catalysts. The surface morphology of the BPE/HDPE blends studied by scanning electron microscopy (SEM) revealed low miscibility between the PE phases mainly in the case of the polymer blends produced at high temperature (50 ºC).
Macromolecular Chemistry and Physics, 2014
An anilinonaphthoquinone-ligated nickel complex [Ni(C 10 H 5 O 2 NC 6 H 3-2,6-iPr 2)(Ph)(PPh 3)] (1) activated with silica-supported modifi ed methylaluminoxane is found to be effective for ethylene polymerization under atmospheric pressure at low Al/Ni ratio. The activity of this system becomes maximal at 60 °C with a steady polymerization rate. The molecular weight of the produced polymer monotonously decreases with raising polymerization temperature, but the high-molecularweight polymer with the number-average molecular weight of 119 000 g mol −1 is obtained even at 80 °C. The produced polymer possesses methyl branches, the content of which is increased by raising the polymerization temperature. Consequently, the melting point of the produced polymer decreases from 130 to 120 °C by raising the polymerization temperature from 40 to 80 °C. Many papers have been reported on the heterogenization of homogeneous metallocene catalysts from the industrial point of view. [ 4 ] Nickel diimine catalysts were also supported on solid carriers, of which methods can be classifi ed into two categories. One is to heterogenize activators, and the other is to heterogenize nickel complexes. A typical procedure for the former is a combination of silica-supported methylaluminoxane (MAO) with a nickel complex. [ 5 ] This procedure is very simple, but often causes the decrease of activity compared with the corresponding homogeneous system. The low activity of the silica-supported MAO system should be ascribed to the steric hindrance around the active species because the counter anion locates on the bulky solid surface. In order to overcome this demerit, the other type of supported catalyst has been developed, where the ligand of the nickel complex is supported on the solid surface through a linker. [ 6 ] The nickel catalysts thus prepared were reported to show good activity for ethylene polymerization, although the synthetic routes of the catalysts usually become more complicated.
Ethylene Polymerization Catalyzed by Neutral Nickel(II) Complex with O^N-Chelating Ligand
Polymer Journal, 2004
We have achieved the synthesis of neutral nickel catalyst with the modified O^N-chelating ligand for the ethylene polymerization. The activity of the catalyst, and the molecular weight and the branching structure of the polymer obtained strongly depend on the ligand structure as well as the presence of Ni(COD) 2 which is used as an activator. The crystal structure of the catalyst was determined and the long nickel-phosphine bond length seems to play an important role for increasing the polymerization activity.
Journal of Organometallic Chemistry, 2013
A series of 2,6-dibenzhydryl-N-(2-phenyliminoacenaphthylenylidene)-4-chloroanilines (L1eL5) and their nickel halide complexes LNiX 2 (X ¼ Br, C1eC5; X ¼ Cl, C6eC10) were synthesized. All organic compounds were characterized by FT-IR and NMR spectroscopy and elemental analysis. The nickel complexes were characterized by FT-IR spectroscopy, elemental analysis and their structures were determined by single-crystal X-ray diffraction. Upon activation with MAO, all of these nickel complexes showed high activities (up to 10 7 g of PE (mol of Ni) À1 h À1) for ethylene polymerization. The resulting polyethylenes possess high molecular weights (M w up to 10 6 g mol À1) and feature high degrees of branching. The MM-QEq method was employed to assess the ligands' effects on catalytic activities. The results show that higher net charges on the nickel core correlate directly with higher measured activities.
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.
Ethylene polymerization by sterically and electronically modulated Ni(II) α-diimine complexes
Journal of Polymer Science Part A: Polymer Chemistry, 2008
A series of highly active ethylene polymerization catalysts based on bidendate a-diimine ligands coordinated to nickel are reported. The ligands are prepared via the condensation of bulky ortho-substituted anilines bearing remote pushpull substituents with acenaphthenequinone, and the precatalysts are prepared via coordination of these ligands to (DME)NiBr 2 (DME ¼ 1,2-dimethoxyethane) to form complexes having general formula [ZN ¼ C(An)-C(An) ¼ NZ]NiBr 2 [Z ¼ (4-NH 2-3,5-C 6 H 2 R 2) 2 CH(4-C 6 H 4 Y); An, acenaphthene quinone; R, Me, Et, iPr; Y ¼ H, NO 2 , OCH 3 ]. When activated with methylaluminoxane (MAO) or common alkyl aluminiums such as ethyl aluminium sesquichloride (EAS) all catalysts polymerize ethylene with activities exceeding 10 7 g-PE/ mol-Ni h atm at 30 8C and atmospheric pressure. Among the cocatalysts used EAS records the best activity. Effects of remote substituents on ethylene polymerization activity are also investigated. The change in potential of metal center induced by remote substituents, as evidenced by cyclic voltammetric measurements, influences the polymerization activity. UV-visible spectroscopic data have specified the important role of cocatalyst in the stabilization of nickel-based active species. A tentative interpretation based on the formation of active and dormant species has been discussed. The resulting polyethylene was characterized by high molecular weight and relatively broad molecular weight distribution, and their microstructure varied with the structure of catalyst and cocatalyst.