Selective Chain Transfer Reactions in Metallocene Catalyzed Copolymerization of Ethylene with Allylbenzene

Byun, Doo-Jin; Kim, Sang Youl

doi:10.1021/ma9913459

Cited by 65 publications

(37 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Both for early as well as late metal systems, significant amounts of chain transfer to aluminum are only observed when bulky ligands are employed. 108 In addition, catalyzed chain growth has only been observed with metal catalysts containing bulky ligands, such as 2,6-diisopropylphenyl or mesityl substituted bis(imino)-pyridine iron catalysts, in combination with dialkyl zinc, or pentamethylcyclopentadienyl lanthanide and actinide based systems with magnesium or aluminum alkyls, respectively. These bulky ligands are believed to destabilize the ground-state bimetallic species, i.e., disfavor the formation of too stable an adduct between the transition metal alkyl and the chain transfer agent (pathway C in Scheme 3).…”

Section: Discussionmentioning

confidence: 99%

Iron Catalyzed Polyethylene Chain Growth on Zinc: A Study of the Factors Delineating Chain TransferversusCatalyzed Chain Growth in Zinc and Related Metal Alkyl Systems

et al. 2004

View full text Add to dashboard Cite

The bis(imino)pyridine iron complex, [[2,6-(MeC=N-2,6-iPr2C6H3)2C5H)N]FeCl2] (1), in combination with MAO and ZnEt2 (> 500 equiv.), is shown to catalyze polyethylene chain growth on zinc. The catalyzed chain growth process is characterized by an exceptionally fast and reversible exchange of the growing polymer chains between the iron and zinc centers. Upon hydrolysis of the resultant ZnR2 product, a Poisson distribution of linear alkanes is obtained; linear alpha-olefins with a Poisson distribution can be generated via a nickel-catalyzed displacement reaction. Other dialkylzinc reagents such as ZnMe2 and ZniPr2 also show catalyzed chain growth; in the case of ZnMe2 a slight broadening of the product distribution is observed. The products obtained from Zn(CH2Ph)2 show evidence for chain transfer but not catalyzed chain growth, whereas ZnPh2 shows no evidence for chain transfer. The Group 13 metal alkyl reagents AlR3 (R = Me, Et, octyl, IBu) and GaR3 (R = Et, nBu) act as highly efficient chain transfer agents, whereas GaMe3 exhibits behavior close to catalyzed chain growth. LinBu, MgnBu2 and BEt3 result in very low activity catalyst systems. SnMe4 and PbEt4 give active catalysts, but with very little chain transfer to Sn or Pb. The remarkably efficient iron catalyzed chain growth reaction for ZnEt2 compared to other metal alkyls can be rationalized on the basis of: (1) relatively low steric hindrance around the zinc center, (2) their monomeric nature in solution, (3) the relatively weak Zn-C bond, and (4) a reasonably close match in Zn-C and Fe-C bond strengths.

show abstract

Section: Discussionmentioning

confidence: 99%

Iron Catalyzed Polyethylene Chain Growth on Zinc: A Study of the Factors Delineating Chain TransferversusCatalyzed Chain Growth in Zinc and Related Metal Alkyl Systems

et al. 2004

View full text Add to dashboard Cite

show abstract

“…For most metallocene‐based catalysts, β‐H transfer to a metal or monomer, producing equimolar unsaturated and saturated end groups, is the dominant chain‐transfer process, whereas chain transfer to aluminum and β‐methyl transfer to a metal play rather minor roles in polymerization reactions. There are several exceptional cases for which obvious chain transfer to aluminum or β‐methyl has been reported 1–6…”

Section: Introductionmentioning

confidence: 99%

Effect of alkylaluminum on ethylene polymerization catalyzed by 2,6‐bis(imino)pyridyl complexes of Fe(II)

Wang

Fan

2005

J. Polym. Sci. A Polym. Chem.

View full text Add to dashboard Cite

In the presence of tetraethylaluminoxane (TEAO), iron complexes were used to catalyze ethylene polymerizations with extremely high activities and generally produced polyethylene with a bimodal molecular weight distribution (MWD). This bimodal MWD of polyethylene was mainly derived from residual triethylaluminum in TEAO and was produced through a mechanism of chain transfer to aluminum. Ethylaluminoxane and tetraisobutylaluminoxane also were used to polymerize ethylene with high activities in the presence of iron complexes, and only polyethylene with a unimodal MWD was produced. The ratio of the rate constant of chain transfer to aluminum (ktrA) to the rate constant of chain propagation (kp) was determined to be 0.12 for {[ArNC(Me)]2C5H3N}FeCl2 when Ar was 2,6‐diisopropylphenyl (1) and 2.48 for {[ArNC(Me)]2C5H3N}FeCl2 when Ar was 2,6‐dimethylphenyl (2); these values are far larger than those for metallocene‐based catalysts. This explains why an iron complex usually produces polyethylene with a broader MWD than metallocene‐based catalysts. Additionally, it can be concluded from the great difference between 1 and 2 with respect to ktrA/kp that an iron complex with less congested aryl substituents is subjected to chain transfer to aluminum. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1599–1606, 2005

show abstract

“…This is in complete agreement with previously obtained information regarding comonomer distribution as a function of molar mass. 34,38 The lower M w of the copolymer is associated with more comonomer being used and can be directly related to the comonomer facilitating chain transfer reactions 39,40 , that is, b-H elimination, or chain transfer to aluminum.…”

Section: Chemical Composition Separationmentioning

confidence: 99%

Ethylene/1‐heptene copolymers as interesting alternatives to 1‐octene‐based LLDPE: Molecular structure and physical properties

Ndiripo

Joubert

Pasch

2015

J. Polym. Sci. Part A: Polym. Chem.

View full text Add to dashboard Cite

Classical linear low density polyethylenes (LLDPEs) are copolymers of ethylene and 1-octene or 1-hexene, respectively. In the past, other 1-olefins have been tested as comonomers but the resulting LLDPEs were never commercialized as large scale products. The present study focuses on the use of 1-heptene as an interesting comonomer for the synthesis of LLDPE. For a comparison of the molecular structure and the physical properties of 1-heptene-and 1-octene-based LLDPEs, five Ziegler-Natta LLDPEs of varying comonomer contents based on 1-heptene and 1-octene, respectively, were acquired and analysed using advanced methods. The comonomer contents of the resins were between 0.35 and 6.4 mol %. Crystallization-based techniques revealed similar bimodal distributions that are due to the formation of copolymer and polyethylene homopolymer fractions. The compositional distribution of the copolymers was studied by high-temperature (HT) HPLC and HT-2D-LC. The analytical results indicate similar chemical heterogeneities and molar mass distributions of the two sets of LLDPE up to a comonomer content of 3 mol %. Similar to the molecular structure, the physical properties of the materials are quite similar. At comonomer contents of 3 mol % differences between the two sets of samples are seen that are attributed to differences in the abilities of 1-heptene and 1-octene in disrupting the crystal arrangements of the polymer chains in solid state. V C 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 962-975

show abstract

Selective Chain Transfer Reactions in Metallocene Catalyzed Copolymerization of Ethylene with Allylbenzene

Cited by 65 publications

References 25 publications

Iron Catalyzed Polyethylene Chain Growth on Zinc: A Study of the Factors Delineating Chain TransferversusCatalyzed Chain Growth in Zinc and Related Metal Alkyl Systems

Iron Catalyzed Polyethylene Chain Growth on Zinc: A Study of the Factors Delineating Chain TransferversusCatalyzed Chain Growth in Zinc and Related Metal Alkyl Systems

Effect of alkylaluminum on ethylene polymerization catalyzed by 2,6‐bis(imino)pyridyl complexes of Fe(II)

Ethylene/1‐heptene copolymers as interesting alternatives to 1‐octene‐based LLDPE: Molecular structure and physical properties

Contact Info

Product

Resources

About