Experimental and theoretical investigations of the structure of methylaluminoxane (MAO) cocatalysts for olefin polymerization

Ystenes, Martin; Eilertsen, Jan L.; Liu, Jianke; Ott, Matthias; Rytter, Erling; St�vneng, Jon A.

doi:10.1002/1099-0518(20000901)38:17<3106::aid-pola120>3.0.co;2-t

Cited by 95 publications

(44 citation statements)

References 51 publications

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“…Rytter is convinced that three units are sufficient because bridging methyl groups are already existing. 57 By IRand UV-investigations we found that the metallocene and MAO rapidly form a complex (Fig. 10).…”

Section: Activation Mechanismmentioning

confidence: 99%

The discovery of metallocene catalysts and their present state of the art

Kaminsky

2004

J. Polym. Sci. A Polym. Chem.

361

221

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Metallocene and other transition metal complexes activated by methylaluminoxane are highly active catalysts for the polymerization of olefins, diolefins, and styrene, which was discovered at the University of Hamburg about 25 years ago. These catalysts allow the synthesis of polymers with a highly defined microstructure, tacticity, and stereoregularity, as well as new copolymers with superior properties such as film clarity, tensile strength, and lower extractables. A better understanding of the mechanism of olefin polymerization leads to findings of other new single site catalysts. The development of the metallocene/MAO-catalysts from their discovery to their present state of the art is presented. Keywords:metallocene catalysts; methylaluminoxane; olefin polymerization; zirconocene complexes; polyolefins; single site catalysis Dr. Kaminsky received his Ph.D. and degree in chemistry from Hamburg University, Germany in 1971 for investigating the side reactions of biscyclopentadienyl-zirconiumdichloride and triethylaluminum. He then served as lecturer and continued his research on the determination of zirconocene/aluminumalkyl-complexes and recycling of polymers by pyrolysis in a fluidized bed process. During that time he and Hansjörg Sinn discovered that the activity of metallocenes and other transition metals can be increased extremely by the addition of MAO as a cocatalyst. In 1979 he became full professor at the University of Hamburg for Technical and Macromolecular Chemistry and has served as director, dean, and president of German chemical society, Hamburg section. Dr. Kaminsky has received the following honors and rewards: elected to the

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Section: Activation Mechanismmentioning

confidence: 99%

The discovery of metallocene catalysts and their present state of the art

Kaminsky

2004

J. Polym. Sci. A Polym. Chem.

361

221

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“…Concerning TMA effects on copolymerization by homogeneous metallocenes, there are not many reports in the literature, but for supported metallocene catalysts, such studies have been reported 19, 20. However, for ethene homopolymerization, several authors have discussed the effect of TMA 21–26. The influence of TMA is catalyst‐specific.…”

Section: Introductionmentioning

confidence: 99%

Pressure and trimethylaluminum effects on ethene/1‐hexene copolymerization with methylaluminoxane‐activated (1,2,4‐Me₃Cp)₂ZrCl₂: Trimethylaluminum suppression of standard termination reactions after 1‐hexene insertion

Bruaseth

Bahr

Gerhard

et al. 2005

J. Polym. Sci. A Polym. Chem.

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Ethene homopolymerizations and copolymerizations with 1-hexene were catalyzed by methylaluminoxane-activated (1,2,4-Me 3 Cp) 2 ZrCl 2 . Investigations of the effects of various pressures on the homopolymerizations and copolymerizations and of the effects of different concentrations of trimethylaluminum (TMA) on the copolymerizations were performed. The characteristics of the ethene/1-hexene copolymers agreed with expectations for changes in the ethene concentration: the incorporation of 1-hexene decreased, whereas the melting point and crystallinity increased, with increasing pressure. The main termination mechanism of the homopolymerizations was ␤-hydrogen transfer to the monomer. Termination mechanisms resulting in vinylidene unsaturations dominated in the copolymerizations. Standard termination mechanisms producing vinyl and trans-vinylene unsaturations occurred in parallel and were not influenced by the ethene or TMA concentration. In addition, some chain transfer to TMA, producing saturated end groups after hydrolysis, occurred. Copolymerizations with different additions of TMA, with the other polymerization conditions kept constant, showed that the catalytic productivity [tons of polyethylene/(mol of Zr h)], the 1-hexene incorporation, and the molecular weight (from gel permeation chromatography) were independent of the TMA concentration. Surprisingly, the vinylidene content decreased almost linearly with increasing TMA concentration. TMA might have coordinated to the catalytic site after 1-hexene insertion and rotation to the ␤-agostic state and, therefore, suppressed the standard termination reactions after 1-hexene insertion.

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“…The observed common composition distribution broadness demonstrates the presence of strong micromixing/segregation effect [58][59][60]. This phenomenon can be ascribed to the three-dimensional MAO cage structures that feature the following [61][62][63][64][65][66][67][68]:…”

Section: Copolymer Inter-chain Composition Distribution and Copolymermentioning

confidence: 99%

Metallocene-catalyzed ethylene−α-olefin isomeric copolymerization: A perspective from hydrodynamic boundary layer mass transfer and design of MAO anion

Adamu

Atiqullah

Malaibari

et al. 2016

Journal of the Taiwan Institute of Chemical Engineers

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Keywords:Metallocene catalyst Pseudo-homogeneous and in-situ heterogeneous isomeric ethylene−α-olefin copolymerization Hydrodynamic boundary layer mass transfer Inter-and intra-chain backbone composition distribution Lamellar thickness distribution Thermal properties a b s t r a c t This study reports a novel conceptual framework that can be easily experimented to evaluate the effects of hydrodynamic boundary layer mass transfer, methylaluminoxane (MAO) anion design, and comonomer steric hindrance on metallocene-catalyzed ethylene polymerization. This approach was illustrated by conducting homo-and isomeric copolymerization of ethylene with 1-hexene and 4-methyl-1-pentene in the presence of bis(n-butylcyclopentadienyl) zirconium dichloride ( n BuCp) 2 ZrCl 2 , using (i) MAO anion 1 (unsupported [MAOCl 2 ] − ) and pseudo-homogeneous reference polymerization, and (ii) MAO anion 2 (supported Si−O−[MAOCl 2 ] − ) and in-situ heterogeneous polymerization. The measured polymer morphology, catalyst productivity, molecular weight distribution, and inter-chain composition distribution were related to the locus of polymerization, comonomer effect, in-situ chain transfer process, and micromixing effect, respectively. The peak melting and crystallization temperatures and %crystallinity were mathematically correlated to the parameters of microstructural composition distributions, melt fractionation temperatures, and average lamellar thickness. These relations showed to be insightful. The comonomer-induced enchainment defects and the eventual partial disruption of the crystal lattice were successfully modeled using Flory and GibbsThompson equations. The present methodology can also be applied to study ethylene−α-olefin copolymerization, performed using MAO-activated non-metallocene precatalysts.

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Experimental and theoretical investigations of the structure of methylaluminoxane (MAO) cocatalysts for olefin polymerization

Cited by 95 publications

References 51 publications

The discovery of metallocene catalysts and their present state of the art

The discovery of metallocene catalysts and their present state of the art

Pressure and trimethylaluminum effects on ethene/1‐hexene copolymerization with methylaluminoxane‐activated (1,2,4‐Me₃Cp)₂ZrCl₂: Trimethylaluminum suppression of standard termination reactions after 1‐hexene insertion

Metallocene-catalyzed ethylene−α-olefin isomeric copolymerization: A perspective from hydrodynamic boundary layer mass transfer and design of MAO anion

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Experimental and theoretical investigations of the structure of methylaluminoxane (MAO) cocatalysts for olefin polymerization

Cited by 95 publications

References 51 publications

The discovery of metallocene catalysts and their present state of the art

The discovery of metallocene catalysts and their present state of the art

Pressure and trimethylaluminum effects on ethene/1‐hexene copolymerization with methylaluminoxane‐activated (1,2,4‐Me3Cp)2ZrCl2: Trimethylaluminum suppression of standard termination reactions after 1‐hexene insertion

Metallocene-catalyzed ethylene−α-olefin isomeric copolymerization: A perspective from hydrodynamic boundary layer mass transfer and design of MAO anion

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Pressure and trimethylaluminum effects on ethene/1‐hexene copolymerization with methylaluminoxane‐activated (1,2,4‐Me₃Cp)₂ZrCl₂: Trimethylaluminum suppression of standard termination reactions after 1‐hexene insertion