D/A‐metallocenes: the new dimension in catalyst design

Starzewski, Aleksander Ostoja

doi:10.1002/masy.200450906

Cited by 11 publications

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“…Other nontraditional bridges include R 2 E (E = Ge, Sn) (35), as well as an alkyl boryl (36), and one with nitrogen that can bind directly to the transition metal (37). The bridge shown in 6 employs a Lewis acid-Lewis base interaction between P and B atoms; the metallocene gives highly isotactic polypropylene (iPP) at low temperatures, indicating the bridge can be robust under polymerization conditions (38,39 (44), which is proposed (45) to have a half-sandwich chromium center as shown in equation 7. This catalyst exhibits facile chain transfer to H 2 , poor comonomer incorporation, and polymers of fairly broad MWD.…”

Section: Bridged Sandwich Complexes Bridged (Or Ansa-) Metallocenesmentioning

confidence: 97%

Metallocenes

Kuhlman¹

2016

Encyclopedia of Polymer Science and Technology

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Once narrowly defined as metal complexes of precise chemical formula (η 5 ‐C 5 H 5 ) 2 M, the word “metallocene” has evolved to represent a versatile class of polymerization technology that is slowly but significantly reshaping the polyolefin industry. Metallocene catalysts enable production of polyethylenes with narrow molecular weight and composition distributions, efficient incorporation of standard and nonstandard comonomers, an excellent spectrum of tacticity control in poly‐α‐olefins, and remarkable adaptability enabled by accumulated scientific endeavors relating ligand designs to polymer microstructures. Olefin polymerization is reviewed in some detail with emphasis on commercially relevant technologies, and a brief commercial overview is included. Nonpolymerization catalysis and (co)polymerization of functional monomers are also briefly summarized.

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Section: Bridged Sandwich Complexes Bridged (Or Ansa-) Metallocenesmentioning

confidence: 97%

Metallocenes

Kuhlman¹

2016

Encyclopedia of Polymer Science and Technology

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“…The ansa catalysts show higher comonomer incorporation than non‐bridged catalysts 10, 27–30. Since the discovery of bridged catalysts, much research has been focused on catalyst design and the role of the bridges in catalytic performance 30–36. In recent research it has been found that addition of substituents to ligands can improve catalyst activity and comonomer incorporation ability 3, 37–43.…”

Section: Introductionmentioning

confidence: 99%

Copolymerization of ethylene/α‐olefins using bis(2‐phenylindenyl)zirconium dichloride metallocene catalyst: structural study of comonomer distribution

Mortazavi

Arabi

Zohuri

et al. 2010

Polymer International

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Catalysts have a major role in the polymerization of olefins and exert their influence in three ways: (1) polymerization behaviour, including polymerization activity and kinetics; (2) polymer particle morphology, including bulk density, particle size, particle size distribution and particle shape; and (3) polymer microstructure, including molecular weight regulation, chemical composition distribution and short-and long-chain branching. By tailoring the catalyst structure, such as the creation of a bridge or introducing a substituent on the ligand, metallocene catalysts can play a major role in the achievement of desirable properties. Kinetic profiles of the metallocene catalyst used in this study showed decay-type behaviour for copolymerization of ethylene/α-olefins. It was observed that increasing the comonomer ratio in the feedstock affected physical properties such as reducing the melting temperature, crystallinity, density and molecular weight of the copolymers. It was also observed that the heterogeneity of the chemical composition distribution and the physical properties were enhanced as the comonomer molecular weight was increased. In particular, 2-phenyl substitution on the indenyl ring reduced somewhat the melting point of the copolymers. In addition, the copolymer produced using bis(2-phenylindenyl)zirconium dichloride (bis(2-PhInd)ZrCl 2 ) catalyst exhibited a narrower distribution of lamellae (0.3-0.9 nm) than the polymer produced using bisindenylzirconium dichloride catalyst (0.5-3.6 nm). The results obtained indicate that the bis(2-PhInd)ZrCl 2 catalyst showed a good comonomer incorporation ability. The heterogeneity of the chemical composition distribution and the physical properties were influenced by the type of comonomer and type of substituent in the catalyst.

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“…During the past 25 years, metallocene complexes have been extensively studied as catalysts for the homogeneous and heterogeneous polymerization of α‐olefins 1–26. For industrial applications, heterogeneous catalyst systems are preferred since the amount of the expensive cocatalyst MAO27–35 can be significantly reduced and “reactor fouling” is avoided.…”

Section: Introductionmentioning

confidence: 99%

μ‐Gels as support materials for dinuclear olefin polymerization catalysts

Schilling

Görl

Alt

2008

J of Applied Polymer Sci

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μ‐Gels which consist of poly(organosilicon) networks can be employed as efficient support materials for ethylene polymerization catalyst precursors. Alkylaluminum cocatalysts can be fixed on the μ‐gel surfaces using the PHT (“partially hydrolyzed trimethylaluminum”) method. The influence of different aluminum/water ratios on the ethylene polymerization properties of these heterogeneous systems is investigated. Dinuclear silicon bridged zirconium complexes are used as catalyst precursors yielding polyethylenes with broad or bimodal molecular weight distributions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

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D/A‐metallocenes: the new dimension in catalyst design

Cited by 11 publications

References 0 publications

Metallocenes

Metallocenes

Copolymerization of ethylene/α‐olefins using bis(2‐phenylindenyl)zirconium dichloride metallocene catalyst: structural study of comonomer distribution

μ‐Gels as support materials for dinuclear olefin polymerization catalysts

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