Ethylene polymerization of the new titanium complexes bearing a phosphine oxide‐bridged bisphenolato ligand

A series of novel titanium(IV) complexes combining a phosphine oxide‐bridged bisphenolato ligand TiCl₂{2,2′‐O?P‐R₃ (4‐R₂‐6‐R₁‐C₆H₂O)₂}(THF) ( 6a : R₁ = tBu, R₂ = H, R₃ = Ph; 6b : R₁ = Ph, R₂ = H, R₃ = Ph; 6c : R₁ = R₂ = tBu, R₃ = Ph; 6d : R₁ = R₂ = cumyl, R₃ = Ph; 6e : R₁ = tBu, R₂ = H, R₃ = PhF₅) were prepared by the reaction of corresponding bisphenolato ligands with TiCl₄ in THF. X‐ray analysis reveals that complex 6a adopts distorted octahedral geometry around the titanium center. These catalysts were performed for ethylene polymerization in the presence of modified methyaluminoxane (MMAO). The effects of reaction parameters on ethylene polymerization behaviors, such as cocatalyst concentration, polymerization temperature, and reaction time were studied in detail. In general, these new complexes exhibited high catalytic activity, good temperature tolerance, and long lifetime for ethylene polymerization. The resulting polymers possess high molecular weight, unimodal distribution, and linear structure. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7062–7073, 2008     

Synthesis and characterization of phosphorous-bridged bisphenoxy titanium complexes and their application to ethylene polymerization

Phosphorous-bridged bisphenoxy titanium complexes were synthesized and their ethylene polymerization behavior was investigated. Bis[3-tert-butyl-5-methyl-2-phenoxy](phenyl)phosphine tetrahydrofuran titanium dichloride (4a) was obtained by treatment of 3 equiv of n-BuLi with bis[3-tert-butyl-2-hydroxy-5-methylphenyl](phenyl)phosphine hydrochloride salt (3a) followed by TiCl₄(THF)₂ in THF. THF-free complexes 5a-5d were synthesized more conveniently by the direct reaction of MOM-protected ligands (2a-2d) with TiCl₄ in toluene. X-ray analysis of 4a revealed that the ligand is bonded to the octahedral titanium (IV) center in a facial fashion and two chlorine atoms possess cis-geometry. Complexes 4a and 5a-5d were utilized as catalyst precursors for ethylene polymerization. Complex 5c gave high molecular weight polyethylene (M_w = 1,170,000, M_w/M_n = 2.0) upon activation with Al(ⁱBu)₃/[Ph₃C][B(C₆F₅)₄] (TB). Ethylene polymerization activity of 5d activated with Al(ⁱBu)₃/TB reached 49.0 × 10⁶ g mol (cat) ⁻¹ h⁻¹.     

Ethylene polymerization by the new chromium catalysts based on amino‐pyrrolide ligands

A series of amino‐pyrrolide ligands ( 1–4a ) and their derivatives amino‐thiophene ligand ( 5a ), amino‐indole ligand ( 6a ) were prepared. Chromium catalysts, which were generated in situ by mixing the ligands with CrCl₃(thf)₃ in toluene, were tested for ethylene polymerization. The preliminary screening results revealed that the tridentate amino‐pyrrolide ligands containing soft pendant donor, 3a, 4a /CrCl₃(thf)₃ systems displayed high catalytic activities towards ethylene polymerization in the presence of modified methyaluminoxane. The electronic and steric factors attached to the ligand backbone significantly affected both the catalyst activity and the polymer molecular weight. Complex 4b was obtained by the reaction of CrCl₃(thf)₃ with one equivalent of the lithium salts of 4a , which was the most efficient ligand among the tested ones. The effect of polymerization parameters such as cocatalyst concentration, ethylene pressure, reaction temperature, and time on polymerization behavior were investigated in detail. The resulting polymer obtained by 4b display wax‐like and possess linear structure, low molecular weight, and unimodal distribution. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 713–721, 2009     

Ethylene and propylene polymerization by the new substituted bridged (cyclopentadienyl)(fluorenyl) zirconocenes

Eight Cs‐symmetric complexes, R₁R₂C(Cp)(Flu)MCl₂ [R₁ = R₂ = CH₃CH₂CH₂, M = Zr (1), Hf (2); R₁ = R₂ = p? CH₃OC₆H₄, M = Zr (3), Hf (4); R₁ = p? ^tBuC₆H₄, R₂ = Ph, M = Zr (5), Hf (6); R₁ = R₂ = p? ^tBuC₆H₄, M = Zr (7); R₁ = R₂ = PhCH₂, M = Zr (8)] have been synthesized and characterized. Zirconocenes all showed the same high catalytic activities in ethylene polymerization as complex Ph₂C(Cp)(Flu)ZrCl₂ (9). However, in the propylene polymerization, the catalytic activities decreased in the order 5 ≈ 9 > 7 > 8. Introduction of ^tBu decreased the activities, probably due to the bulk steric hindrance. The polypropylene produced by 5 and 7 with ^tBu substituent showed a higher molecular weight (Mη) than that produced by 9. The ¹³C NMR spectrum revealed the polymers from 7 and 8 to have shorter average syndiotactic block length than polymer produced by 9. It was noted that [mm] stereodefect of polypropylene by 8 could not be observed from ¹³C NMR, which showed that the benzyl on bridge carbon 8 prevented chain epimerization and enatiofacial misinsertion in polymerization. Copyright © 2005 John Wiley & Sons, Ltd.     

Ethylene (co-)polymerization by long-lifetime half-sandwich zirconium catalyst bearing a [SSO]-carborane ligand

Half-sandwich zirconium complex 3 containing tridentate carborane [S,S,O] ligand 2 [(HOC6H2R2-4,6)(CH2)SC(B10H10) C(Ph)2P=S, R=tBu] was synthesized by the reaction of CpZrCl3(Cp=η5-C5H5) with sodium salt of ligand 2. Zirconium complex 3 was characterized by elemental and NMR analyses. DFT calculations were also performed on complex 3 to analyze the stereochemistry. The results from DFT calculations indicate that structure S1, in which no sulfur atom bonds to the zirconium atom, exists at the lowest energy level. In the presence of methylaluminoxane(MAO), complex 3 exhibited good catalytic activities for ethylene polymerization and long life-time up to 10 h. Moreover, the complex 3/MAO system displayed excellent catalytic activities toword ethylene copolymerization with 1-hexene or polar olefins.     

Synthesis,structure characterization and catalytic activity of lanthanide complexes containing an ansa carbonous‐bridged cyclopentadienyl—thienyl ligand

A kind of new lanthanocene complex with an ansa carbonous‐bridged cyclopentadienyl/aromatic heterocycle ligand was prepared and characterized. Based on the data of elemental analyses, MS and IR, they were presumed to be solvent‐free complexes (cyclo‐C₄H₃SCMe₂C₅H₄)₂LnCl [Ln = Er (1), Dd ( 2 ), Y ( 3 ), Sm ( 4 )]. These complexes were effective for the polymerization of methyl methacrylate in the presence of co‐catalyst. When AlEt₃ and NaH (nanometric) were used as different co‐catalysts, the lanthanocene complexes 1–4 showed different catalytic behavior. These differences resulted from the formation of different active species. The catalyst system (cyclo‐C₄H₃SCMe₂C₅H₄)₂LnCl/NaH (nanometric) showed high catalytic activity (yield ≥ 95% and Mη > 10⁵) in a short time at the ambient temperature. Copyright © 2008 John Wiley & Sons, Ltd.     

Ethylene polymerization reactions with Ziegler–Natta catalysts. I. Ethylene polymerization kinetics and kinetic mechanism

Kinetics of ethylene homopolymerization reactions and ethylene/1-hexene copolymerization reactions using a supported Ziegler–Natta catalyst was carried out over a broad range of reaction conditions. The kinetic data were analyzed using a concept of multicenter catalysis with different centers that respond differently to changes in reaction parameters. The catalyst contains five types of active centers that differ in the molecular weights of material they produce and in their copolymerization ability. In ethylene homopolymerization reactions, each active center has a high reaction order with respect to ethylene concentration, close to the second order. In ethylene/α-olefin copolymerization reactions, the centers that have poor copolymerization ability retain this high reaction order, whereas the centers that have good copolymerization ability change the reaction order to the first order. Hydrogen depresses activity of each type of center in the homopolymerization reactions in a reversible manner; however, the centers that copolymerize ethylene and α-olefins well are not depressed if an α-olefin is present in the reaction medium. Introduction of an α-olefin significantly increases activity of those centers, which are effective in copolymerizing it with ethylene but does not affect the centers that copolymerize ethylene and α-olefins poorly. To explain these kinetic features, a new reaction scheme is proposed. It is based on a hypothesis that the Ti—C₂H₅ bond in active centers has low reactivity due to the equilibrium formation of a Ti—C₂H₅ species with the H atom in the methyl group β-agostically coordinated to the Ti atom in an active center. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4255–4272, 1999     

Ethylene polymerization with long‐lifetime monopendant thienyl‐substituted group 4 metallocenes

A series of group 4 metallocenes (RCp)[Cp―(bridge)―(2‐C₄H₃S)]MCl₂ [M = Ti ( C1 , C2 , C3 , C4 ); M = Zr ( C5 , C6 , C7 , C8 )] bearing a pendant thiophene group on a cyclopentadienyl ring have been synthesized, characterized and tested as catalyst precursors for ethylene polymerization. The molecular structures of representative titanocenes C2 and C4 were confirmed by single‐crystal X‐ray diffraction and revealed that both complexes exist in an expected coordination environment for a monomeric bent metallocene. No intramolecular coordination between the thiophene group and the titanium center could be observed in the solid state. Upon activation by methylaluminoxane (MAO), titanocenes C1 , C2 , C3 , C4 showed moderate catalytic activities and produced high‐ or ultra‐high‐molecular‐weight polyethylene (M_v 70.5–227.1 × 10⁴ g mol^?1). Titanocene C3 is more active and long‐lived, with a lifetime of nearly 9 h at 30 °C. At elevated temperatures of 80–110 °C, zirconocenes C5 , C6 , C7 , C8 displayed high catalytic activities (up to 27.6 × 10⁵ g PE (mol Zr)^?1 h^?1), giving high‐molecular‐weight polyethylene (M_v 11.2–53.7 × 10⁴ g mol^?1). Even at 80 °C, a long lifetime of at least 2 h was observed for the C8/MAO catalyst system. Copyright © 2014 John Wiley & Sons, Ltd.     

Ethylene polymerization by sterically and electronically modulated Ni(II) α‐diimine complexes

A series of highly active ethylene polymerization catalysts based on bidendate α‐diimine ligands coordinated to nickel are reported. The ligands are prepared via the condensation of bulky ortho‐substituted anilines bearing remote push–pull substituents with acenaphthenequinone, and the precatalysts are prepared via coordination of these ligands to (DME)NiBr₂ (DME = 1,2‐dimethoxyethane) to form complexes having general formula [ZN = C(An)‐C(An) = NZ]NiBr₂ [Z = (4‐NH₂‐3,5‐C₆H₂R₂)₂CH(4‐C₆H₄Y); An, acenaphthene quinone; R, Me, Et, iPr; Y = H, NO₂, OCH₃]. When activated with methylaluminoxane (MAO) or common alkyl aluminiums such as ethyl aluminium sesquichloride (EAS) all catalysts polymerize ethylene with activities exceeding 10⁷ g‐PE/ mol‐Ni h atm at 30 °C 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. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1066–1082, 2008     

Half‐titanocene complexes bearing dianionic 6‐benzimidazolylpyridyl‐2‐carboximidate ligands: Synthesis,characterization, and their ethylene polymerization

6‐Benzimidazolylpyridyl‐2‐carboximidic half‐titanocene complexes, Cp′TiLCl (Cp′ = C₅H₅, MeC₅H₄, C₅Me₅, L = 6‐benzimidazolylpyridine‐2‐carboxylimidic, C1–C13 ), were synthesized and characterized along with single‐crystal X‐ray diffraction. The half‐titanocene chlorides containing substituted cyclopentadienyl groups, especially pentamethylcyclopentadienyl groups were more stable, while those without substituents on the cyclopentadienyl groups were easily transformed into their dimeric oxo‐bridged complexes, (CpTiL)₂O ( C14 and C15 ). In the presence of excessive amounts of methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all half‐titanocene complexes showed high catalytic activities for ethylene polymerization. The substituents on the Cp groups affected the catalytic behaviors of the complexes significantly, with less substituents favoring increased activities and higher molecular weights of the resultant polyethylenes. Effects of reaction conditions on catalytic behaviors were systematically investigated with catalytic systems of mononuclear C1 and dimeric C14 . With C1 /MAO, large MAO amount significantly increases the catalytic activity, while the temperature only has a slight effect on the productivity. In the case of C14 /MAO catalytic system, temperature above 60 °C and Al/Ti value higher than 5000 were necessary to observe good catalytic activities. In both systems, higher reaction temperature and low cocatalyst amount gave the polyethylenes with higher molecular weights. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3396–3410, 2008     

Dichlorovanadium (IV) complexes with salen‐type ligands for ethylene polymerization

Vanadium complexes with tetradentate salen‐type ligands were first time explored in ethylene polymerizations. The effects of the vanadium complex structure, the alkyl aluminum cocatalysts type (EtAlCl₂, Et₂AlCl, Et₃Al, and MAO), and the polymerization conditions (Al/V molar ratio, temperature) on polyethylene yield were explored. It was found that EtAlCl₂ in conjunction with investigated vanadium complexes produced the most efficient catalytic systems. It was shown, moreover, that the structural changes of the tetradentate salen ligand (type of bridge which bond donor nitrogen atoms and type of substituent on aryl rings) affected activity of the catalytic system. The complexes containing ligands with cyclohexylene bridges were more active than those with ethylene bridges. Furthermore, the presence of electron‐withdrawing groups at the para position and electron‐donating substituents at the ortho position on the aryl rings of the ligands resulted in improved activity in relation to the systems with no substituents (with the exception of bulky t‐Bu group). The results presented also revealed that all vanadium complexes activated by common organoaluminum compounds gave linear polyethylenes with high melting points (134.8–137.6 °C), high molecular weights, and broad molecular weight distribution. The polymer produced in the presence of MAO possesses clearly lower melting point (131.4 °C) and some side groups (around 9/1000 C). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6940–6949, 2008     

Copolymerization of ethylene with 1‐hexene promoted by novel multi‐chelated non‐metallocene complexes with imine bridged imidazole ligand

A series of novel bridged multi‐chelated non‐metallocene catalysts is synthesized by the treatment of N,N‐imidazole, N,N‐dimethylimidazole, and N,N‐benzimidazole with n‐BuLi, 2,6‐dimethylaniline, and MCl₄ (M = Ti, Zr) in THF. These catalysts are used for copolymerization of ethylene with 1‐hexene after activated by methylaluminoxane (MAO). The effects of polymerization temperature, Al/M molar ratio, and pressure of monomer on ethylene copolymerization behaviors are investigated in detail. These results reveal that these catalysts are favorable for copolymerization of ethylene with 1‐hexene featured high catalytic activity and high comonomer incorporation. The copolymer is characterized by ¹³C NMR, WAXD, GPC, and DSC. The results confirm that the obtained copolymer features broad molecular weight distribution (MWD) about 33–35 and high 1‐hexene incorporation up to 9.2 mol %, melting temperature of the copolymer depends on the content of 1‐hexene incorporation within the copolymer chain and 1‐hexene unit in the copolymer chain isolates by ethylene units. The homopolymer of ethylene has broader MWD with 42–46. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 417–424, 2010     

Study of the Crystal Structure of Oxo‐bridged Binuclear FeIII Complex with Chiral Salen Ligand

A oxo‐bridged binuclear iron complex with chiral salen ligand [Fe₂L₂]O (H₂L = R, R'‐N, N'‐bis (3,5‐di‐tert‐butylsalicylaldene)‐1, 2‐cyclohexanediamine) has been synthesized and the structure has been determined by X‐ray diffraction analysis. The title complex crystallizes in triclinic system with space group P‐1. Crystal data: a = 1.42555(14) nm, b = 1.54889 (15) nm, c = 1.83662 (17) run, = 103.873(2)°, β = 100.506(2)°, 7=101.840(2)°, V = 3.7371 nm³, D_c = 1.082 g/cm³ and Z = 2. In the complex, each iron center is penta‐coordination and in distorted square‐pyramidal environment. Two Fe^m atoms are intramolecularity bridged by an oxygen atom with Fe‐Fe nonbond distance of 0.3517(3) nm.     

Well‐controlled ring‐opening polymerization of cyclic esters catalyzed by aluminum amido complexes: Kinetics and mechanism

A series of aluminum dimethyl complexes 1 – 6 bearing N‐[2‐(pyrrolidinyl)benzyl]anilido ligands were synthesized and well characterized. The molecular structure of complex 1 determined by an X‐ray diffraction study indicates the bidentate chelating mode of the pyrrolidinyl‐anilido ligand. In the absence of a coinitiator, these complexes exhibited excellent control toward the polymerizations of ε‐caprolactone and rac‐lactide, affording polyesters with quite narrow molecular weight distributions (M_w/M_n = 1.04–1.26). The end group analysis of ε?CL oligomer via ¹H NMR and ESI‐TOF MS methods gave strong support to the hypothesis that the polymerization catalyzed by these aluminum complexes proceeds via a coordination‐insertion mechanism involving a unique Al? N (amido) bond initiation. Via ¹H NMR scale oligomerization studies, it is suggested that the insertion of the first lactide monomer into Al? N bond of the complex is much easier than the insertion of lactide monomer into the newly formed Al? O (lactate) bond and might also be easier than the insertion of the first ε?CL monomer into Al? N bond. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3096–3106     

Synthesis,Structures and DFT Studies of Imido‐bridged and (Bis)ligand‐coordinated Titanium Complexes

Syntheses and structures of five imido‐bridged dinuclear titanium complexes and two (bis)ligand‐coordinated mononuclear titanium complexes are reported. Addition of 1 or 2 equiv. of Schiff base ligand (((1H‐pyrrol‐2‐yl)methylene)amino)‐2,3‐dihydro‐1H‐inden‐2‐ol (H₂L) to Ti(NMe₂)₄ resulted in transamination with 4 equiv. of dimethylamides generating a (bis)ligand‐coordinated complex Ti(L)₂ ( 1 ). Treatment of Ti(NMe₂)₄ with 1 equiv. of ^tBuNH₂ followed by addition of 1 equiv. of H₂L afforded an imido‐bridged complex [Ti(L)(N^tBu)]₂ ( 2 ). 1:1:1:1 reaction of Ti(NMe₂)₄/RNH₂/H₂L/py(or phen) produced imido‐bridgedcomplexes [Ti(L)(NPh)(py)]₂ ( 3 ), [Ti(L)(4‐F‐PhN)(py)]₂·Tol ( 4 ·Tol), [Ti(L)(4‐Cl‐PhN)(py)]₂·Tol·THF ( 5 ·Tol·THF), [Ti(L)(4‐Br‐PhN)(py)]₂·Tol ( 6 ·Tol) and a (bis)ligand‐coordinated complex Ti(L)₂·phen ( 7 ) (py = pyridine, phen = 1,10‐phenanthroline). Attempts to prepare the monomeric titianium imido complexes were unsuccessful. DFT studies show that the assumed compound which contains Ti = N species is less stable than imido‐bridged Ti‐N(R)‐Ti complexes, providing the better understanding of the experimental results.     

Ethylene polymerization with imine and phosphine nickel complexes containing isothiocyanate

Three isothiocyanate complexes of nickel(II) containing diimine [ArN?C(Me)? C(Me)?NAr]Ni‐ (NCS)₂ (1), iminophosphine [Ph₂PC₆H₄CH?NAr]Ni(NCS)₂ (2), or diphosphine (dppe)Ni(NCS)₂ (3), [Ar = 2, 6‐ⁱPr‐C₆H₃; dppe = 1, 2‐bis(diphenylphosphine)ethane] were synthesized and examined for ethylene polymerization activated by methylaluminoxane (MAO). Their behavior was compared with those of the corresponding halide analogues [ArN?C(Me)? C(Me)?NAr]NiBr₂ (4), [Ph₂PC₆H₄CH?NAr]NiBr₂ (5), and (dppe)NiCl₂ (6). The diimines showed the highest polymerization activity. Replacement of the halide for the NCS pseudo halide affected the activity and decreased the molecular weight of the polymer formed. The highest molecular weights were obtained with the diimine complexes. Highly branched polyethylenes were obtained with the bulkier complexes 1 and 4. Replacement of the halide for NCS in the diimine complexes also caused an increase in the branching content, whereas the opposite occurs for the iminophosphine complexes. The different activities and behavior of the catalyst systems with halide versus NCS in the polymerization of ethylene and the characteristics of the final products suggest a modification in the active species caused by the non‐chelating ligand. Polymer molecular weight and branching content is dependent on the MAO/Ni molar ratio and on the working temperature. Copyright © 2004 John Wiley & Sons, Ltd.     

Ethylene polymerization by novel 4,4′-bis(methylene)biphenylene bridged homodinuclear titanocene and zirconocene combined with MAO

4,4′-Bis(methylene)biphenylene bridged homodinuclear titanocene (3) and zirconocene (4) have been synthesized by treatment of CpTiCl₃ and CpZrCl₃ · DME with Na₂[C₅H₄CH₂C₆H₄-p-C₆H₄CH₂C₅H₄], respectively, in THF and characterized by ¹H NMR and element analysis. After activation with methyl aluminoxane (MAO), these catalysts were used for the homogeneous polymerization of ethylene. The influences of reaction conditions, such as temperature, time, catalyst concentration and molar ratio of MAO/Cat. on ethylene polymerization were investigated in detail. The catalytic activities of 3 and 4 are more than three times higher than that of the phenyldimethylene bridged homodinuclear metallocene of titanocene (5) and zirconocene (6), respectively, and also twice higher than that of Cp₂TiCl₂/MAO and Cp₂ZrCl₂/MAO, respectively. However, the catalytic activity of 3 is nearly half as high as that of 4, which reached 1.31 × 10⁶ g PE/mol cat h. The molecular weight of polyethylene increases simultaneously with prolongation of polymerization time. GPC spectra show that 3 and 4 produce polyethylene with broad molecular weight distribution (4.28 and 3.18). The high melting points of the products (131-134 °C) indicate that the polyethylene formed is highly linear and highly crystalline.     

Ethylene polymerization using novel titanium catalytic precursors bearing N,N‐dialkylcarbamato ligands

Polymerization catalysts based on N,N‐dialkylcarbamato complexes of titanium(IV) appear particularly interesting, because these novel catalytic precursors are rather cheap and easy to synthesize and handle. This contribution reports ethylene polymerization behavior of titanium(IV) complexes of general formula Ti(O₂CNR₂)₄ R = Me ( I ) and Et ( II ) and TiCl₂(O₂CNMe₂)₂ ( III ). These precursors in conjunction with methylaluminoxane resulted active catalysts for the polymerization of ethylene, affording high‐density polyethylene with limited branch content. The influence of the polymerization parameters was studied with particular reference to the type of catalyst components, solvent, temperature, monomer concentration, and Al/Ti ratio. The nature of the solvent appears crucial for catalytic performances: when toluene was replaced by chlorobenzene, a significant increase of the productivity was ascertained. The obtained polymers were characterized by DSC, size exclusion chromatography, FTIR, and NMR techniques. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Effect of experimental conditions on ethylene polymerization with in‐situ‐supported metallocene catalyst

Ethylene polymerization was carried out with a novel in‐situ‐supported metallocene catalyst that eliminates the need for a supporting step before polymerization. The influence of the metallocene amount, aluminum to zirconium mole ratio, temperature, pressure, and cocatalyst type on polymerization kinetics and molecular weight distribution of the produced polyethylene was studied. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1803–1810, 2000