Soluble neodymium chloride 2-ethylhexanol complex as a highly active catalyst for controlled isoprene polymerization

Soluble NdCl₃·3EHOH (2-ethyl hexanol) in hexane combined with AlEt₃ is highly active for isoprene polymerization in hexane. The NdCl₃·3EHOH/AlEt₃ has higher activity than the typical binary catalyst NdCl₃·3ⁱPrOH (isopropanol)/AlEt₃ and ternary catalyst NdV₃ (neodymium versatate)/AlEt₂Cl/Al(i-Bu)₂H. The molecular weight of polyisoprenes can be controlled by variation of [Nd], [Al]/[Nd] ratio and polymerization temperature and time. The NdCl₃·3EHOH/AlEt₃ catalyst polymerized isoprene to afford products featuring high cis-1,4 stereospecificity (ca. 96%), high molecular weight (ca. 10⁵) and relatively narrow molecular weight distributions (M_w/M_n = 2.0-2.8) simultaneously. More importantly, some living polymerization characteristics were demonstrated: (a) absence of chain termination; (b) linear correlation between M_n and polymer yield; (c) increment of molecular weight in the ‘seeding’ polymerization. Though some deviation from the typical living polymerization such as molecular weight distribution is not narrow enough and the line of M_n and polymer yield does not extrapolate to zero, controlled polymerization with the current catalyst can still be concluded.     

Novel Neodymium-Based Ternary Catalyst, Nd(Oi-Pr)3/[HNMe2Ph]+[B(C6F5)4]-/i-Bu3Al, for Isoprene Polymerization

Summary Polymerization of isoprene was investigated by using a novel ternary catalyst system composed of neodymium(III) isopropoxide (Nd(OiPr)₃), dimethylphenylammonium tetrakis(pentafluorophenyl)borate ([HNMe₂Ph]⁺[B(C₆F₅)₄]^-; borate), and triisobutylaluminum (i-Bu₃Al). The mole ratios of borate and aluminum compounds to Nd catalyst significantly affected the polymerization behavior. Both yield and cis-1,4 content of polyisoprene decreased in the case of [borate]/[Nd] < 1.0, while at [borate]/[Nd] > 1.0 the formation of multiple active species resulted in the polymer showing bimodal peaks in GPC. When the [Al]/[Nd] ratio was lower than 30, the polymer yield sharply decreased, whereas the cis-1,4 content became relatively low with use of a large excess of Al ([Al]/[Nd] > 50). Thus, the optimal catalyst composition was [Nd]/[borate]/[Al] = 1/1/30, which gave in > 97% yield polyisoprene with high molecular weight (M_n2×10⁵) and relatively narrow molecular weight distribution (M_w/M_n2.0) and mainly cis-1,4 structure (90%).     

Polymerization of vinyl chloride with butyllithiums and metallocene catalysts

Polymerizations of vinyl chloride (VC) with butyllithium (BuLi) and metallocene catalysts were investigated. In the polymerization of VC with BuLi, the activity for polymerization decreased in the following order; t‐BuLi > n‐BuLi > s‐BuLi. A polymer controlled structurally in the main chain was found to be synthesized from the polymerization of VC with BuLi. The molecular weights of polymers obtained in bulk polymerization were higher than those of polymers obtained in solution. A linear relationship of the M_n of the polymer and the polymer yields was observed. The M_w/M_n of the polymer did not change significantly during polymerization, although the M_w/M_n was around 2. Thermal stability of the polymer obtained with BuLi was higher than that of polymer obtained with radical initiators, as determined by TGA measurements. In the polymerization of VC with Cp*TiX₃/MAO (X: Cl and OCH₃) catalysts, polymers were obtained with both catalysts, although the rate of polymerization was slow. The Cp*Ti(OCH₃)₃//MAO catalyst in CH₂Cl₂ gave higher‐molecular‐weight polymers in a better yield than in toluene. From elemental analysis and the NMR spectra of the polymers, the Cp*Ti(OCH₃)₃/MAO catalyst gave polymers consisting of repeating regular head‐to‐tail units, in contrast to the Cp*TiCl₃/MAO catalyst, which gave polymers having anomalous units.     

Polymerization of styrene using bis(β‐ketoamino)nickel(II)/methylaluminoxane catalytic systems

Styrene (St) was polymerized in toluene solution by using bis(β‐ketoamino)nickel(II) complex as the catalyst precursor and methylaluminoxane (MAO) as the cocatalyst. The polymerization conditions, such as Al : Ni ratio, monomer concentration, reaction temperature, and polymerization time, were studied in detail. Both of the bis(β‐ketoamino)nickel(II)/MAO catalytic systems exhibited higher activity for polymerization of styrene, and polymerization gave moderate molecular weight of polystyrene with relatively narrow molecular weight distribution (M_w/M_n < 1.6). The obtained polymer was confirmed to be atactic polystyrene by analyzing the stereo‐triad distributions mm, mr, and rr of aromatic carbon C¹ in NMR spectrum of the polymer. The mechanism of the polymerization was also discussed and a metal–carbon coordination mechanism was proposed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

An activated neodymium‐based catalyst for styrene polymerization

Coordination polymerization of styrene with a ternary catalyst system composed of catalyst neodymium tricarboxylate (Nd), co‐catalyst Al(i‐Bu)₃ (Al) and chlorinating agent trichloroethane (Cl) was carried out in cyclohexane. The effects of the catalyst system preparation procedure and of the reaction conditions on catalytic activity, molecular weight and molecular weight distribution of the resultant polymers were investigated. The catalytic activity depended mainly on the molar ratios of Al/Nd and of Cl/Nd and on the ageing temperature and polymerization temperature. High polymerization conversion and high catalytic activity could be obtained at high Al/Nd ratios and/or at high ageing temperature. The catalyst system exhibited high activity of 8.32 × 10⁴ g polystyrene (mol Nd h)^?1 at 50 °C. The molecular weight of the polymers obtained reached high weight‐average (M_w) values (M_w = 4.35 × 10⁵ g mol^?1) when Al/Nd = 8, but relatively low values (6000–11 000 g mol^?1) at high Al/Nd ratios. Copyright © 2005 Society of Chemical Industry     

Homogeneous neodymium iso-propoxide/modified methylaluminoxane catalyst for isoprene polymerization

The neodymium iso-propoxide [Nd(Oi-Pr)₃] catalyst activated by modified methylaluminoxane (MMAO) is homogeneous and effective in isoprene polymerization in heptane to provide polymers with high molecular weight (M_n∼10⁵), narrow molecular weight distribution (M_w/M_n=1.1-2.0) and mainly cis-1,4 structure (82-93%). The polymer yield increased with increasing [Al]/[Nd] ratio (50-300 mole ratio) and polymerization temperature (0-60 °C), while the molecular weight and cis-1,4 content decreased. On the other hand, the same catalyst resulted in relatively low polymer yield and low molecular weight in toluene. The cyclized polyisoprene was formed in dichloromethane, which is attributable to the cationic active species derived from MMAO alone. When chlorine sources (Et₂AlCl, t-BuCl, Me₃SiCl) were added, the cis-1,4 stereoregularity of polymer improved up to 95% even at a high temperature of 60 °C, though the polymer yield decreased.     

Structure of active centers,their stereospecificity distribution,and multiplicity in diene polymerization initiated by NdCl3‐based catalytic systems

On the basis of quantum‐chemical calculations, it was shown that among six types of active centers (ACs) that can form during the polymerization of butadiene with lanthanide‐based catalytic systems, five types (containing electron‐accepting chlorine atoms in the coordination sphere of a lanthanide) exhibit a π‐allyl binding of the terminal unit of a growing polymer chain to a lanthanide atom and function as cis‐regulating. The sixth type of ACs is characterized by a σ‐alkyl structure and shows a trans‐stereospecificity. This results was used to interpret the data on the microstructure of polybutadiene prepared using NdCl₃ · 3TBP‐Al(iso‐C₄H₉)₃, NdCl₃ · 3TBP–Mg(n‐C₄H₉)(iso‐C₈H₁₇) catalytic systems and their combinations (TBP is tributyl phosphate). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 601–603, 2003     

Morphology and activity of nanosized NdCl3 catalyst for 1,3‐butadiene polymerization

The binary lanthanide catalyst for 1,3‐butadiene was invented for 40 years ago. However, it has not been employed in commercial application due to its poor solubility and low activity. Nanosized neodymium chloride (NdCl₃) was prepared in tetrahydrofuran (THF) medium through dissolution, chelation, and colloidal formation steps. Anhydrous NdCl₃ was dissolved in THF, and ca. 1.5 THF molecules were coordinated. In the colloidal formation step, THF was slowly replaced with the addition of cyclohexane, and pale blue nuclei, nanosize below 200 nm, were formed. The structural studies for NdCl₃ · xTHF using X‐ray powder diffraction (XRD) and scanning electron microscope (SEM) indicate that high ordered crystallinity is decreased with reduced particle size from trigonal prismatic to porous sphere structure. Nano NdCl₃, obtained as colloidal state in cyclohexane, was activated with Al(iBu)₃ and Al(iBu)₂H at room temperature and employed for 1,3‐butadiene solution polymerization. The nanosized Nd catalysts showed high activity (1.0 ～ 1.3 × 10⁵ g/Nd mol · h), which is comparable to that of the ternary neodymium catalyst Nd(neodecanoate)₃/AlEt₂Cl/Al(iBu)₃. The microstructures of polybutadiene, cis, trans, and vinyl, are about 96.0, 3.5, and 0.5%, respectively. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1279–1283, 2005     

Polymerization of vinyl chloride with Cp*Ti(OPh)3/MAO catalyst in toluene

Polymerization of vinyl chloride (VC) with a Cp*Ti(OPh)₃/MAO catalyst in toluene was investigated. The polymerization rate was lower than that in CH₂Cl₂, and the mm triad concentration of the PVC obtained in toluene was somewhat higher than that of the PVC obtained in CH₂Cl₂. As the polymerization in toluene proceeded at a considerable rate, a kinetic study of this polymerization was undertaken. The polymer yield increased with reaction time, and the molecular weight of the polymer increased with increasing polymer yield. The M_w/M_n ratio of the polymer decreased with increasing polymerization temperature. The initiator efficiency of the catalyst was low at the initial stage of the polymerization in toluene, but it reached nearly 100% when the polymerization was carried out for more than 30 h. The control of both themolecular weight of PVC and its main‐chain structure was found to be possible in the polymerization of VC with the Cp*Ti(OPh)₃/MAO catalyst in toluene. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers     

Comparative study of propylene polymerization using monosupported and bisupported titanium‐based Ziegler–Natta catalysts

Heterogeneous Ziegler–Natta systems—MgCl₂ (ethoxide type)/TiCl₄/di‐n‐butyl phthalate (DNBP)/triethylaluminum (TEA)/dimethoxymethylcyclohexylsilane (DMMCHS) and SiO₂/MgCl₂ (ethoxide type)/TiCl₄/DNBP/TEA/DMMCHS—were studied for the polymerization of propylene. The slurry polymerization of propylene was carried out with the catalyst systems in n‐heptane. Both systems performed with optimum activity at a particular [Al]/[DMMCHS]/[Ti] molar ratio. The ratio to reach the highest activity was much lower for the bisupported catalyst system. The productivity of the bisupported catalyst was higher than that of the monosupported one. Polypropylene of a high isotacticity index (II; >96%) was obtained with both systems and did not significantly change with an increasing [Al]/[DMMCHS]/[Ti] molar ratio. The addition of hydrogen as a chain‐transfer agent reduced II of the polymers obtained with both systems. The effect of the polymerization temperature (40–75°C) on the viscosity‐average molecular weight (M_v) and II showed a decrease in both cases. The bisupported catalyst system produced a polymer with higher M_v. The effect of temperature on II was similar for both the monosupported and bisupported systems. A monomer pressure of 2.02 × 10⁵ to 0.8 × 10⁶ Pa increased M_v of the obtained polymer. II of the polymer slightly decreased with increasing monomer pressure. The titanium content of the catalyst was 1.70 and 3.55% for the monosupported and bisupported systems, respectively. The surface area of the bisupported catalyst was higher than that of the monosupported catalyst. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2220–2226, 2006     

Bulk polymerization of vinyl chloride with half-titanocene/MAO catalyst

Bulk polymerization of vinyl chloride (VC) with Cp^∗Ti(OPh)₃/MAO catalyst was investigated. The bulk polymerization of VC with Cp^∗Ti(OPh)₃/MAO catalyst proceeded to give poly(vinyl chloride) (PVC) with high molecular weight in good yields. The M_n of the polymer increased in direct proportion to polymer yields and the line passed through the origin. The M_w/M_n of the polymer decreased with an increase of polymer yield. The GPC elution curves were unimodal and the whole curves shifted clearly to the higher molecular weight as a function of reaction time. This indicates that the control of molecular weight can be achieved in the polymerization of VC with Cp^∗Ti(OPh)₃/MAO catalyst even in bulk. The structure of PVC obtained from the bulk polymerization of VC with Cp^∗Ti(OPh)₃/MAO catalyst consists of a regular structure. The thermal stability of the polymer obtained with Cp^∗Ti(OPh)/MAO catalyst was higher than that of PVC obtained from radical polymerization and depended on the molecular weight of the polymer. In contrast to that, the initial decomposition temperature of the polymer obtained from a radical polymerization did not depend on the molecular weight. We presumed that the decomposition of the polymer obtained with Cp^∗Ti(OPh)₃/MAO catalyst initiated at the chain end.     

Nanosized silica‐supported metallocene/MAO catalyst for propylene polymerization

A nanosized silica particle was used as the support to prepare an Et[Ind]₂ZrCl₂/MAO catalyst for propylene polymerization of polypropylene. The catalyst and the polymer produced were characterized with nitrogen adsorption, ICP, DSC, SEM, TEM, XRD, solution viscometer, ¹³C NMR and optical microscopy. The effects of polymerization temperature and [Al]/[Zr] ratio on catalyst activity and polymer melting point were investigated. Under identical reaction conditions, nanosized catalyst exhibited better polymerization activity than the microsized catalyst (e.g., the former had 64% higher activity than the latter at the optimum polymerization temperature (50°C) and [Al]/[Zr] = 570). DSC results indicated that polymer melting point increased with the increase of [Al]/[Zr] ratio and with the decrease of polymerization temperature. XRD results showed that the percentage of γ crystals increased with decreasing [Al]/[Zr] ratio. Electron microscopic results showed that the polymer particle size increased with increasing polymerization temperature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2573–2580, 2006     

New fluorine‐containing bissalicylidenimine–titanium complexes for olefin polymerization

Three new titanium complexes bearing salicylidenimine ligands—bis[(salicylidene)‐2,3,5,6‐tetrafluoroanilinato]titanium(IV) dichloride ( 1 ), bis[(3,5‐di‐tert‐butylsalicylidene)‐2,3,5,6‐tetrafluoroanilinato]titanium(IV) dichloride ( 2 ), and bis[(3,5‐di‐tert‐butylsalicylidene)‐4‐trifluoromethyl‐2,3,5,6‐tetrafluoroanilinato]titanium(IV) dichloride ( 3 )—were synthesized. The catalytic activities of 1 – 3 for ethylene polymerization were studied with poly(methylaluminoxane) (MAO) as a cocatalyst. Complex 1 was inactive in ethylene polymerization. Complex 2 at a molar ratio of cocatalyst to pre catalyst of Al_MAO/Ti = 400–1600 showed very high activity in ethylene polymerization comparable to that of the most efficient metallocene complexes and titanium compounds with phenoxy imine and indolide imine chelating ligands. It gave linear high‐molecular‐weight polyethylene [weight‐average molecular weight (M_w) ≥ 1,700,000. weight‐average molecular weight/number‐average molecular weight (M_w/M_n) = 4–5] with a melting point of 142°C. The ability of the 2 /MAO system to copolymerize ethylene with hexene‐1 in toluene was analyzed. No measurable incorporation of the comonomer was observed at 1:1 and 2:1 hexene‐1/ethylene molar ratios. However, the addition of hexene‐1 had a considerable stabilizing effect on the ethylene consumption rate and lowered the melting point of the resultant polymer to 132°C. The 2 /MAO system exhibited low activity for propylene polymerization in a medium of the liquid monomer. The polymer that formed was high‐molecular‐weight atactic polypropylene (M_w ～ 870,000, M_w/M_n = 9–10) showing elastomeric behavior. The activity of 3 /MAO in ethylene polymerization was approximately 70 times lower than that of the 2 /MAO system. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1040–1049, 2005     

Copolymerization of phenylisocyanate and ϵ‐caprolactone with rare earth chloride systems

A copolymer of phenylisocyanate (PhNCO) and ε‐caprolactone (CL) was synthesized by the rare earth chloride systems lanthanide chloride isopropanol complex (LnCl₃·3iPrOH) and propylene epoxide (PO). Polymerization conditions were investigated, such as lanthanides, reaction temperature, monomer feed ratio, La/PO molar ratio, and aging time of catalyst. The optimum conditions were: LaCl₃ preferable, [PhNCO]/[CL] in feed = 1 : 1 (molar ratio), 30°C, [monomer]/[La] = 200, [PO]/[La] = 20, aging 15 min, polymerization in bulk for 6 h. Under such conditions the copolymer obtained had 39 mol % PhNCO with a 78.2% yield, M_n = 20.3 × 10³, and M_w/M_n = 1.60. The copolymers were characterized by GPC, TGA, ¹H‐NMR, and ¹³C‐NMR, and the results showed that the copolymer obtained had a blocky structure with long sequences of each monomer unit. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2135–2140, 2007     

Polymerization of n-Hexyl Isocyanate with Rare Earth Catalyst Composed of Nd(P204)3/Al(i-Bu)3

Summary Rare earth catalyst system: lanthanide phosphonate/tri-i-butyl aluminum (Nd(P₂₀₄)₃/Al(i-Bu)₃) has been found for the first time as a novel catalyst for the polymerization of n-hexyl isocyanate (HNCO). Nd(P₂₀₄)₃ and Nd(P₅₀₇)₃ are the commercial names of neodymium 2-ethylhexyl phosphonates, their formulas are shown in table 1. The catalyst can be prepared easily by mixing Nd(P₂₀₄)₃ and Al(i-Bu)₃. The effects of catalyst, solvent, reaction temperature and time on the polymerization of HNCO were studied. The obtained poly (n-hexyl isocyanate) (PHNCO) was characterized by GPC, FT-IR, ¹H-NMR and TGA. The resulting PHNCO had molecular weight (Mn=39.6×10⁴, Mv=67.2×10⁴), molecular weight distribution (MWD=2.44) and yield (82.7%) under the moderate reaction conditions: catalyst concentration [Nd]=6.65×10^-2mol/L, Al/Nd=10 molar ratio, [HNCO]/[Nd]=100 molar ratio, at -10^oC for 10h in bulk. Relatively high reaction temperature (-10^oC) is the most distinct virtue. The IR and NMR analyses show that the polymer obtained is not polyether but polyisocyanate.     

Polymerization of 1,3‐butadiene with VO(P204)2 activated by methylaluminoxane,purified methylaluminoxane,and trimethylaluminum

The effect of different aluminum‐based cocatalysts (MAO, pMAO, and TMA) on butadiene (Bd) polymerization catalyzed by VO(P204)2 was investigated. The bimodal dependence of the polymer yield on the [MAO]/[V] molar ratio was revealed, and an highest polymer yield was achieved at a rather low [MAO]/[V] molar ratio ([MAO]/[V] = 13). The microstructures of the resulting poly(Bd)s were also significantly influenced by the ratio. In the TMA or pMAO system, the polymer yields were also very sensitive to the [Al]/[V] molar ratio. However, the microstructures of the resulting poly(Bd)s were almost independent of the ratio. In relation to the microstructures of poly(Bd)s obtained by the MAO and TMA systems at various temperatures, the 1,2‐unit contents were found to be the most abundant microstructure for both systems. In the pMAO system, the trans‐1,4‐units were the most abundant. The results of the additions of Lewis bases (THF and TPP) into Bd polyerization system comfirmed the existing of the two types of the reactions of VO(P₂₀₄)₂‐MAO catalyst and had the polymerization process controlled to some extent. The different thermal behaviors of these catalytic systems also show that multiple types of active centers were formed during the reaction between VO(P₂₀₄)₂ and MAO. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Reversible coordinative chain transfer polymerization of isoprene and copolymerization with ε-caprolactone by neodymium-based catalyst

Coordinative chain transfer polymerization (CCTP) of isoprene was investigated by using the typical Ziegler–Natta catalytic system [Nd(Oi-Pr)₃/Al(i-Bu)₂H/Me₂SiCl₂] with Al(i-Bu)₂H as cocatalyst and chain transfer agent (CTA). The catalyst system exhibited high catalytic efficiency for the reversible CCTP of isoprene and yielded 6–8 polymer chains per Nd atom due to the high chain transfer ability of Al(i-Bu)₂H. The narrow molecular weight distribution (M_w/M_n = 1.22–1.45) of the polymers, the good linear relationship between the M_n and yield of the polymer, and the feasible seeding polymerization of isoprene indicated the living natures of the catalyst species. Moreover, the living Nd-polyisoprene active species could further initiate the ring-opening polymerization of polar monomer (ε-caprolactone) to afford an amphiphilic block copolymer consisting of cis-1,4-polyisoprene and poly(ε-caprolactone) with controllable molecular weight and narrow molecular weight distribution.     

Concentration effects of methylalumoxane, palladium and nickel pre-catalyst and monomer in the vinyl polymerization of norbornene

Summary The vinyl polymerization of norbornene with di-μ-chloro-bis-(6-methoxybicyclo-[2.2.1]hept-2-ene-5σ,2π)-palladium(II), Ni(acetylacetonate)₂ and Ni(2-ethylhexanoate)₂ in combination with methylalumoxane (MAO) was investigated by varying the molar MAO:metal-complex ratio, the norbornene:metal ratio and the metal concentration. The effects on the catalyst activity could be explained with a complexation equilibrium for the active homogeneous complex. Activity data in combination with polymer analyses suggest that at low, yet economical Al(MAO):metal ratios of 100 the fraction of active metal centers is less than 15%. The turnover frequency for the monomer insertion was found to reach 50 s⁻¹. Polydispersities around M_w/M_n= 2 indicate a coordination polymerization with chain transfer and a single-site character of the active centers. Received:27 February 2001/Revised version:11 November 2001/ Accepted: 20 November 2001     

The synthesis of high molecular weight polybutene‐1 catalyzed by Cp★ Ti(OBz)3/MAO

A new stereoregular polybutene‐1 was synthesized with a novel catalyst precursor η⁵‐pentamethyl cyclopentadienyl titanium tribenzyloxide (CpTi(OBz)₃) and methylaluminoxane (MAO). The effects of polymerization conditions on the catalytic activity, molecular weight and stereoregularity of the products were investigated in detail. It was found the catalyst exhibited highest activity of 91.2 kgPB mol Ti⁻¹ h⁻¹ at T = 30 °C, Al/Ti = 200. The catalytic activity and molecular weight were sensitive to the Al/Ti (mole/mole), polymerization temperature; they also depended on the Ti concentration. The molecular weight of the products increased with decreasing temperature. The structure and properties of the polybutene‐1 were characterized by ¹³C NMR, GPC, DSC and WAXD. The result showed the microstructure of polybutene‐1 extracted by boiling heptane was stereoregular, whereas the ether‐soluble fraction was atactic. The molecular weight of polybutene‐1 was over one million g mol⁻¹ and its molecular weight distribution ( M _w/ M _n) was from 1.1 to 1.2. © 2001 Society of Chemical Industry     

Cocatalytic activities of methylaluminoxane prepared by direct water addition method in ethylene polymerization over Cp2ZrCl2

The characterization of ethylene polymerization behaviors catalyzed over Cp₂ZrCl₂/MAO homogeneous system using methylaluminoxanes prepared by the direct hydrolysis of AlMe₃ (Me=methy1) were reported. The MAO was prepared at the ratio of [H₂O]/[A1]=1 and 0.5 and at three different temperatures, i.e., −40, −60 and −80 °C. The polymerization rate was not decreased with polymerization time when the MAO prepared at the ratio of [H₂O]/[AlMe₃]=l at −60 °C was used as a cocatalyst regardless of the ratio of Al/Zr and the polymerization temperature. The polymerization rate drastically decreased with polymerization time above 60 °C in case of using MAO prepared at the ratio of [H₂O]/[AlMe₃]=l at −80 °C. However, in case of the MAO prepared at the ratio of [H₂O]/ [AlMe₃]=0.5 at −80 °C, the rate continuously increased with polymerization time at the polymerization temperature of 70 °C and 80 °C. The amount of MAO needed to activate Cp₂ZrC1₂ was larger than that of MAO prepared at the ratio of [H₂O]/[A1]=1. The viscosity molecular weight of polyethylene (PE) cocatalyzed with MAO prepared at the ratio of [H₂O]/[Al]=0.5 was lower than that of polyethylene obtained with MAO prepared at the ratio of [H₂O]/[A1]=1.