Influence of Monomer Concentration on the Stereospecificity of 1-Alkene Polymerization Promoted by C2-symmetric ansa-Metallocene Catalysts

Busico, Vincenzo; Cipullo, Roberta

doi:10.1021/ja00099a060

Cited by 151 publications

(134 citation statements)

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“…Norbornene-ethylene copolymers were characterized with 1 H-NMR and 13 C-NMR methods. The spectra were recorded at 100ЊC with 1,1,2,2,-tetrachloroethane as solvent.…”

Section: Methodsmentioning

confidence: 99%

Investigation of the microstructure of metallocene-catalyzed norbornene-ethylene copolymers using NMR spectroscopy

Bergström¹,

Sperlich

Ruotoistenmäki

et al. 1998

J. Polym. Sci. A Polym. Chem.

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Norbornene–ethylene copolymers were prepared using the metallocene catalyst ethylene bis (indenyl) zirconium dichloride with MAO, and their microstructure was characterized with 1H‐NMR and 13C‐NMR methods. From a Cosy 1H‐NMR spectrum it was found that all norbornene units are enchained in the exo‐configuration. The sequence distribution of norbornene units was investigated using 13C‐1H correlations, hmqc for one‐bond correlations, and hmbc for two‐ or three‐bond correlations. It was shown that norbornene diads were formed at a high norbornene content (45 mol %). When further increasing the norbornene incorporation (66 mol %) a number of new signals were obtained. A Cosy 1H‐NMR spectrum revealed a new crosspeak which, according to the corresponding 13C‐NMR shifts (hmqc), correlated well with a terminal unit of a trimer of norbornene. This means that at very high norbornene contents, norbornene triads can be formed. Because the formation of isotactic norbornene triads is very difficult to understand from a sterical point of view, an epimerization process causing stereoirregularities in the norbornene triad is proposed. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1633–1638, 1998

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“…Norbornene-ethylene copolymers were characterized with 1 H-NMR and 13 C-NMR methods. The spectra were recorded at 100ЊC with 1,1,2,2,-tetrachloroethane as solvent.…”

Section: Methodsmentioning

confidence: 99%

Investigation of the microstructure of metallocene-catalyzed norbornene-ethylene copolymers using NMR spectroscopy

Bergström¹,

Sperlich

Ruotoistenmäki

et al. 1998

J. Polym. Sci. A Polym. Chem.

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show abstract

“…For chain-end control, the parameters Pm and Pr refer to the probability of meso and racemic placements, respectively. A Pm equal to 1 signifies isotacticity, while a Pr equal to 1 indicates syndiotacticity [9,10].…”

Section: Influence Of Structure and Composite Of Ansa-zirconcene Catamentioning

confidence: 99%

“…The racemic catalyst is capable of high enantioselectivity where enantiomorphic site control in propylene polymerization plays a most important role (Scheme 4), while the meso-catalyst obtains primarily atactic PP with the mechanism of chain-end control [10].…”

Section: -Symmetric Ansa-zirconcenementioning

confidence: 99%

“…• C, while the percentage of pentad (mmmm) is over 70% with the metalloene (2, MAO) catalyst system [9,10].…”

Section: -Symmetric Ansa-zirconcenementioning

confidence: 99%

“…In addition, polymerization temperature affects enantioselectivity. It was found that increasing temperature led to the decrease of enantioselectivity [10,14,15]. …”

Section: -Symmetric Ansa-zirconcenementioning

confidence: 99%

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Recent research progress in influence of the ansa-zirconcene catalytic system on the polypropylene microstructure

Xiao

Wang

Liu

et al. 2007

Designed Monomers and Polymers

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Abstract-In this paper, the recent development of ansa-zirconcene catalysts and their co-catalysts, the relationship between the structure of ansa-zirconcene catalytic system and the microstructure of the resultant polypropylene are reviewed. The forming mechanisms of resultant polypropylene microstructure are discussed in view of ansa-zirconcene catalyst structure and their co-catalyst structure.

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Homo- and copolymerization of ethylene at high temperature with cationic zirconocene catalysts

Yano¹,

Sone²,

Yamada³

et al. 1999

Macromol. Chem. Phys.

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SUMMARY: Homo-and copolymerization of ethylene with 1-hexene were conducted at different temperature and ethylene pressure with several zirconocenes activated with dimethylanilinium tetrakis(pentafluorophenyl)borate (Me 2 PhNH N B(C 6 F 5 ) 4 )/triisobutylaluminium (i-Bu 3 Al) to study the effect of ligand structure and polymerization conditions on catalytic activity, molecular weight and chain transfer reactions. At high temperature and low ethylene pressure, rac-ethylene(bisindenyl)zirconium dichloride (rac-Et(Ind) 2 ZrCl 2 ) activated with Me 2 PhNH N B(C 6 F 5 ) 4 /i-Bu 3 Al initially gives a highly active catalyst that is rapidly deactivated. trans-Vinylene double bonds, which were not formed at low temperature, were detected in polyethylene synthesized at high temperature and low ethylene pressure. They reasonably arise from b-H transfer after isomerization reaction. The molecular weight of ethylene/1-hexene copolymers decreases with increasing 1-hexene feed, followed by the formation of vinylidene end groups. This reveals that b-H transfer from propagating chains containing primary inserted 1-hexene as a terminal unit is predominant. This reaction is influenced by the ligand structure. At high temperature and high ethylene pressure, trans-vinylene and vinylidene contents decrease and the vinyl content increases, indicating that the high ethylene pressure controls b-H transfer after isomerization reaction.

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Influence of Monomer Concentration on the Stereospecificity of 1-Alkene Polymerization Promoted by C2-symmetric ansa-Metallocene Catalysts

Abstract: An influence of monomer concentration on the stereospecificity of group 4 ansa-metallocene catalysts for the polymerization of 1-alkenes1 2has been pointed out for Cs-symmetric syndiotacticspecific catalysts. [1][2][3]

Cited by 151 publications

References 0 publications

Investigation of the microstructure of metallocene-catalyzed norbornene-ethylene copolymers using NMR spectroscopy

Investigation of the microstructure of metallocene-catalyzed norbornene-ethylene copolymers using NMR spectroscopy

Recent research progress in influence of the ansa-zirconcene catalytic system on the polypropylene microstructure

Homo- and copolymerization of ethylene at high temperature with cationic zirconocene catalysts

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