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Polymerization Activity (polymerization + activity)
Selected AbstractsSynthesis of polar vinyl monomer,olefin copolymers by ,-diimine nickel catalystPOLYMER INTERNATIONAL, Issue 5 2001Maria M Marques Abstract Vinyl acetate, methyl methacrylate, acrylonitrile and methyl vinyl ketone were investigated for co- and terpolymerization with ethylene and ethylene,propylene. Precursor [bis(N,N,,-dimesitylimino)acenaphthene]dibromonickel, activated by methylaluminoxane was used as a catalyst system and trialkylaluminium was employed to block the polar groups for these polymerizations. Polymerization activities of the order of magnitude of 106 in the case of vinyl acetate and methyl methacrylate, and 105 in the case of acrylonitrile were achieved. Microanalysis and GPC of acrylonitrile copolymers found about 17 units of acrylonitrile per polymer chain. Copolymers with very different properties from the parent homopolymers were obtained in all cases except that of methyl vinyl ketone. © 2001 Society of Chemical Industry [source] Ethene Polymerization Behavior of MAO-Activated Dichloridotitanium Complexes Bearing Bi- and Tetradentate Salicylaldimine DerivativesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 2 2010Antti Pärssinen Abstract New chiral bridged tetradentate (N2O2)TiIVCl2 -type complexes bearing dimethylbiphenyl (1-Ti,3-Ti) and previously published binaphthyl-bridged (4-Ti) complex were synthesized with high yields. This was achieved by treating the corresponding Schiff-base ligand (H2L) precursors with Ti(NMe2)4, followed by conversion of these diamido complexes to LTiCl2 derivatives by the addition of excess of Me3SiCl. A series of unbridged titanium complexes 5-Ti,8-Ti with similar substituents at the phenoxy group were studied and their polymerization properties, after methylaluminoxane (MAO) activation, compared with the above bridged complexes. It was found that the catalysts bearing chiral tetradentate biaryl-bridged salicylaldimine ligands produce multimodal polyethylene (PE) with low activity [below 10 kgPE/(molTi,h,bar)] while their unbridged analogues provide activities that are 10,1000 times greater under similar reaction conditions. The reasons for this dramatic difference in polymerization activities are discussed based on the stabilities of the different cationic species configurations. [source] Nickel(II) and palladium(II) complexes with ,-dioxime ligands as catalysts for the vinyl polymerization of norbornene in combination with methylaluminoxane, tris(pentafluorophenyl)borane, or triethylaluminum cocatalyst systems,JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2002Bernd Berchtold Abstract Nickel(II) and palladium(II) complexes with ,-dioxime ligands dimethylglyoxime, diphenylglyoxime, and 1,2-cyclohexanedionedioxime represent six new precatalysts for the polymerization of norbornene that can be activated with methylaluminoxane (MAO), the organo-Lewis acid tris(pentafluorophenyl)borane [B(C6F5)3], and triethylaluminum (TEA) AlEt3. The palladium but not the nickel precatalysts could also be activated by B(C6F5)3 alone, whereas two of the three nickel precatalysts but none of the palladium systems are somewhat active with only TEA as a cocatalyst. It was possible to achieve very high polymerization activities up to 3.2 · 107 gpolymer/molmetal · h. With the system B(C6F5)3/AlEt3, the activation process can be formulated as the following two-step reaction: (1) B(C6F5)3 and TEA lead to an aryl/alkyl group exchange and result in the formation of Al(C6F5)nEt3,n and B(C6F5)3,nEtn; and (2) Al(C6F5)nEt3,n will then react with the precatalysts to form the active species for the polymerization of norbornene. Variation of the B:Al ratio shows that Al(C6F5)Et2 is sufficient for high activation. Gel permeation chromatography indicated that it was possible to control the molar mass of poly(norbornene)s by TEA or 1-dodecene as chain-transfer agents; the molar mass can be varied in the number-average molecular weight range from 2 · 103 to 9 · 105 g · mol,1. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3604,3614, 2002 [source] Effects of MgCl2 Crystallographic Structure on Active Centre Formation in Immobilized Single-Centre and Ziegler,Natta Catalysts for Ethylene PolymerizationMACROMOLECULAR RAPID COMMUNICATIONS, Issue 21 2008Rubin Huang Abstract The ability of a MgCl2 support to activate a transition metal catalyst has been found to depend both on the crystallographic structure of the support and on the nature of the catalyst. A high degree of crystallographic disorder can be very effective for the immobilization and activation of titanium and vanadium complexes, but is not necessarily effective for zirconocene activation. A highly disordered support prepared by the reaction of MgBu2 with HCl gave high activity with TiCl4 but low activity with (n -PrCp)2ZrCl2. High polymerization activities with the zirconocene were only obtained with supports of type MgCl2/AlRn(OEt)3,n prepared from the reaction of AlR3 with MgCl2,·,1.1EtOH. These supports are characterized by additional peaks in the X-ray diffraction pattern, indicating the presence of a crystalline structure which is absent in the other supports and contains highly Lewis acidic sites able to generate the active metallocenium species. [source] Polymerization of methyl methacrylate using bis(,-ketoamino)nickel(II),MAO catalytic systemsAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 4 2006Xiaohui He Abstract The polymerization of methyl methacrylate (MMA) was investigated using a series of bis(,-ketoamino)nickel(II) complexes in combination with methylaluminoxane in toluene solution. The binary catalyst is necessary for initiating MMA polymerization and producing PMMA with high molecular weights but broad molecular weight distributions. The effects of reaction temperature and Al:Ni molar ratios on the polymerization of MMA were examined in detail. Both steric bulk and electronic effects of the substituents around the imino group in the ligand on MMA polymerization activities could be observed. Relative to electronic effects, the steric hindrance of the ligands displayed a more significant effect on the catalytic activities, with the catalytic activity sequence observed in the order 4 > 1 > 2 > 3 > 5 > 6. Structural analyses of the polymers by 13C NMR spectra indicate that polymerization yields PMMA with a syndiotactic-rich atactic microstructure. Copyright © 2006 John Wiley & Sons, Ltd. [source] Structures and styrene polymerization activities of a series of nickel complexes bearing ligands of pyrazolone derivativesAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 1 2006Feng Bao Abstract A series of nickel complexes with ,-ketoamine ligands based on pyrazolone derivatives were synthesized by condensing pyrazolone with aniline, 2-chloroaniline or naphthylamine and then reacting the produced ,-ketoamine with nickel halide. The solid-state structures of these three complexes were determined by single-crystal X-ray diffraction. The bis(,-ketoamine)nickel complexes are all air-stable and can act as highly active catalyst precursors for styrene polymerization with activation of methylaluminoxane under mild reaction conditions. The activity of the catalyst for styrene polymerization is as high as 2.10 × 105 g polymer/mol Ni h. Both steric and electronic effects were found to be important and influential for catalytic activity. Copyright © 2005 John Wiley & Sons, Ltd. [source] Synthetic Explorations Towards Sterically Crowded 1,2,3-Substituted Bis(indenyl)zirconium(IV) DichloridesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2005Andreas C. Möller Abstract The systematic synthesis of 1,3-dialkyl-substituted 2-silylindenes and their suitability as zirconocene ligands is discussed. Unexpected reactivities rendered a number of substitution patterns unfeasible, especially for alkyl groups other than methyl in 2-(trimethylsilyl)indene derivatives, and essentially for all derivatives of 2-(dimethylsilyl)indene. The syntheses of rac/meso -bis[1-methyl-2-(trimethylsilyl)indenyl]zirconium(IV) dichloride (12) and bis[1,3-dimethyl-2-(trimethylsilyl)indenyl]zirconium(IV) dichloride (13b) are described. The solid-state structure of the latter displays strong deformations within the ligand framework and an unusually large Cpcentroid -Zr,Cpcentroid angle. Both, 12/MAO and 13b/MAO, displayed ethene and ethene-co-1-hexene polymerization activity. Curiously, 13b/MAO shows an extraordinary monomer selectivity, which can be rationalized by means of DFT calculations on the active site. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Dimethylsilylbis(1-indenyl) zirconium dichloride/methylaluminoxane catalyst supported on nanosized silica for propylene polymerizationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2008Kuo-Tseng Li Abstract A dimethylsilylene-bridged metallocene complex, (CH3)2Si(Ind)2ZrCl2, was supported on a nanosized silica particle, whose surface area was mostly external. The resulting catalyst was used to catalyze the polymerization of propylene to polypropylene. Under identical reaction conditions, a nanosized catalyst exhibited much better polymerization activity than a microsized catalyst. At the optimum polymerization temperature of 55°C, the former had 80% higher activity than the latter. In addition, the nanosized catalyst produced a polymer with a greater molecular weight, a narrower molecular weight distribution, and a higher melting point in comparison with the microsized catalyst. The nanosized catalyst's superiority was ascribed to the higher monomer concentration at its external active sites (which were free from internal diffusion resistance) and was also attributed to its much larger surface area. Electron microscopy results showed that the nanosized catalyst produced polymer particles of similar sizes and shapes, indicating that each nanosized catalyst particle had uniform polymerization activity. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Artificial polymerases and molecular chaperonesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2009Akira Harada Abstract Cyclodextrins (CDs) were found to initiate polymerization of lactone to give polyesters with a CD ring at the end of the polymer chain in high yields only by mixing and heating with monomer without cocatalysts or solvents. CD-tethered polyester propagates with the formation of poly-pseudorotaxane, which is necessary to initiate further polymerization. CDs threaded onto the polymer chain are also essential for maintaining the propagating state of the polyester. By polymerizing with CD, switching the activity of the polymerization by photoisomerization was demonstrated. This polymerization system showed specific substrate recognition, releasing the products from the active site. By using the above polymerization system, ,-CD nanospheres which initiates the oligomerization of lactone were constructed. It was found that the formation of poly-pseudorotaxane on the nanosphere enabled further polymerization activity for lactone. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4469,4481, 2009 [source] High molar mass ethene/1-olefin copolymers synthesized with acenaphthyl substituted metallocene catalystsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 1 2008Erkki Aitola Abstract The influence of ligand structure on copolymerization properties of metallocene catalysts was elucidated with three C1 -symmetric methylalumoxane (MAO) activated zirconocene dichlorides, ethylene(1-(7, 9)-diphenylcyclopenta-[a]-acenaphthadienyl-2-phenyl-2-cyclopentadienyl)ZrCl2 (1), ethylene(1-(7, 9)-diphenylcyclopenta-[a]-acenaphthadienyl-2-phenyl-2-fluorenyl)ZrCl2 (2), and ethylene(1-(9)-fluorenyl-(R)1-phenyl-2-(1-indenyl)ZrCl2 (3). Polyethenes produced with 1/MAO had considerable, ca. 10% amount of trans -vinylene end groups, resulting from the chain end isomerization prior to the chain termination. When ethene was copolymerized with 1-hexene or 1-hexadecene using 1/MAO, molar mass of the copolymers varied from high to moderate (531,116 kg/mol) depending on the comonomer feed. At 50% comonomer feed, ethene/1-olefin copolymers with high hexene or hexadecene content (around 10%) were achievable. In the series of catalysts, polyethenes with highest molar mass, up to 985 kg/mol, were obtained with sterically most crowded 2/MAO, but the catalyst was only moderately active to copolymerize higher olefins. Catalyst 3/MAO produced polyethenes with extremely small amounts of trans -vinylene end groups and relatively low molar mass 1-hexene copolymers (from 157 to 38 kg/mol) with similar comonomer content as 1. These results indicate that the catalyst structure, which favors chain end isomerization, is also capable to produce high molar mass 1-olefin copolymers with high comonomer content. In addition, an exceptionally strong synergetic effect of the comonomer on the polymerization activity was observed with catalyst 3/MAO. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 373,382, 2008 [source] Novel cyclohexyl-substituted salicylaldiminato,nickel(II) complex as a catalyst for ethylene homopolymerization and copolymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2004Junquan Sun Abstract The cyclohexyl-substituted salicylaldiminato,Ni(II) complex [O(3-C6H11)(5-CH3)C6H2CHN-2,6-C6H3iPr2]Ni(PPh3)(Ph) (4) has been synthesized and characterized with 1H NMR and X-ray structure analysis. In the presence of phosphine scavengers such as bis(1,5-cyclooctadiene)nickel(0) [Ni(COD)2], triisobutylaluminum (TIBA), and triethylaluminum (TEA), 4 is an active catalyst for ethylene polymerization and copolymerization with the polar monomers tert -butyl-10-undecenoate, methyl-10-undecenoate, and 4-penten-1-ol under mild conditions. The polymerization parameters affecting the catalytic activity and viscosity-average molecular weight of polyethylene, such as the temperature, time, ethylene pressure, and catalyst concentration, are discussed. A polymerization activity of 3.62 × 105 g of PE (mol of Ni h),1 and a weight-average molecular weight of polyethylene of 5.73 × 104 g.mol,1 have been found for 10 ,mol of 4 and a Ni(COD)2/4 ratio of 3 in a 30-mL toluene solution at 45 °C and 12 × 105 Pa of ethylene for 20 min. The polydispersity index of the resulting polyethylene is about 2.04. After the addition of tetrahydrofuran and Et2O to the reaction system, 4 exhibits still high activity for ethylene polymerization. Methyl-10-undecenoate (0.65 mol %), 0.74 mol % tert -butyl-10-undecenoate, and 0.98 mol % 4-penten-1-ol have been incorporated into the polymer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6071,6080, 2004 [source] Studies of ethylene,styrene copolymerization with dinuclear constrained geometry complexes with methyl substitution at the five-membered ring in indenyl of [Ti(,5:,1 -C9H5SiMe2NCMe3)]2 [CH2]nJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 7 2004Seok Kyun Noh Abstract The new dinuclear half-sandwich CGC (constrained geometry catalyst) with methyl substitution in indenyl, [Ti(,5:,1 -2-methylindenyl)SiMe2NCMe3]2 [(CH2)n] [n = 6 (10), n = 9 (11), n = 12 (12)], have been synthesized, and structure of these complexes has been characterized by 1H and 13C NMR. The most important feature is that two protons of methylene directly bonded to the indenyl ring become inequivalent to be shown as two separated resonances at 2.9 and 3.0 ppm, probably due to the formation of planar chirality caused by a titanium complex formation. It has been found that the dinuclear CGCs with methyl substitution at an indenyl ring were very active catalysts for ethylene and styrene copolymerization. The activity increases in the order of 10 < 11 < 12, which indicates that the presence of a longer bridge between two active sites contributes to facilitate the polymerization activity of the dinuclear CGC more effectively. This result might be understood by the implication that the steric factor rather than the electronic factor may play a major role to direct the polymerization behavior of the dinuclear CGC. It is found that the dinuclear catalysts are very efficient to incorporate styrene in the polyethylene backbone. The styrene contents in the formed copolymers ranged from 5 to 40% according to the polymerization conditions. One can observe strong signals at 29.7 ppm of the polyethylene sequences, and, in addition, peaks at 27.5, 36.9, and 46. 2ppm (S,,, S,,, and T,,, respectively) of sequences of EESEE. Weak peak at 25.3 ppm are attributed to S,,, which represents SES sequence. The absence of a signal for T,, at 41.3 ppm and for S,, at 43.6 ppm shows there is no styrene,styrene sequences in copolymers. This result indicates that the dinuclear CGC are very effective to generate well-distributed poly(ethylene- co -styrene)s. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1712,1723, 2004 [source] Syndiospecific polymerization of styrene with BzCpTiCl3 and methylaluminoxane as cocatalystsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2001Constantin Schwecke Abstract Benzyl cyclopentadienyl titanium trichloride (BzCpTiCl3) was synthesized from benzyl bromide, cyclopentadienyl lithium, and titanium tetrachloride and used in combination with methylaluminoxane (MAO) for the syndiospecific polymerization of styrene. Kinetic measurements of the polymerization were carried out at different temperatures. The polymerization with BzCpTiCl3/MAO differs from the polymerization with cyclopentadienyl titanium trichloride in its behavior toward the Al/Ti ratio. In addition, high activities are observed at high Al/Ti ratios. By analyzing the polymerization runs and the physical properties of the polymers with differential scanning calorimetry, 13C NMR spectroscopy, wide-angle X-ray scattering measurements, and gel permeation chromatography, we found that the phenyl ring coordinates to the titanium atom during polymerization. Other known substitutions of the cyclopentadienyl ring (V. Scholz, Dissertation, University of Hamburg, 1998) in principle influence the polymerization activity. The physical properties of the polymers produced by the catalysts already known are nearly identical. BzCpTiCl3 is the first catalyst that leads to polystyrene obviously different from the polystyrene produced by other highly active catalysts. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2805,2812, 2001 [source] High-Throughput Synthesis of New Ni(II), Pd(II), and Co(II) Catalysts and Polymerization of Norbornene Utilizing the Self-Made Parallel Polymerization Reactor SystemMACROMOLECULAR RAPID COMMUNICATIONS, Issue 1 2004Hyun Yong Cho Abstract Summary: We report the development of new Ni(II), Pd(II), and Co(II) catalysts containing ligands of pyrazolylpyridine derivatives by combinatorial and high-throughput synthesis technology. Vinyl type polynorbornene was polymerized utilizing the self-made parallel polymerization reactor system. The Ni(II) catalyst 1 has a polymerization activity of 266.7 kgpolymer,·,molcat,1,·,h,1. We introduce a fast way to conduct catalyst synthesis and high-throughput screening for polymerization. The self-made parallel polymerization reactor system. [source] Ethylene polymerization over MgO-supported zirconocene catalystsPOLYMER ENGINEERING & SCIENCE, Issue 5 2003Soo Jin Kim Supported zirconcene catalysts on a new support, MgO, were prepared and tested in ethylene polymerization. Three types of impregnation methods were employed to find an optimum supporting method for MgO. The direct impregnation of Cp2ZrCl2 on MgO showed low metal loading and polymerization activity, while the catalyst had a higher metal loading and polymerization activity when MgO was treated with methylaluminoxane (MAO) before supporting. Treatment of MgO with MAO during the supporting step invoked two types of catalytic sites, which was evidenced by the bimodal molecular weight distribution of the polymer products. MgO is considered to have potential as a support for metallocenes. [source] UV,visible spectroscopy for zirconocene activation by MAO in olefin polymerization: activity versus wavenumberAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 6 2009Carlos Alonso-Moreno Abstract Activation of ansa -zirconocenes of the type Rac [Zr{1-Me2Si(3-R-(,5 -C9H5))(3-R,-(,5 -C9H5))}Cl2] [R = Et, R, = H (1); R = Pr, R, = H (2); and R = Et, R, = Pr (3), R, R, = Me (4) and R, R, = Bu (5)] by MAO has been studied by UV,visible spectroscopy. Compounds 1,3 have been tested in the polymerization of ethylene at different Al:Zr ratios. UV,vis spectroscopy was used to determine a correlation between the electronic structures of (1,5) and their polymerization activity. Copyright © 2009 John Wiley & Sons, Ltd. [source] | |||||||||||||