Materials Properties Derived from INSITE Metallocene Catalysts

Chum, P. S.; Kruper, William J.; Guest, M. J.

doi:10.1002/1521-4095(200012)12:23<1759::aid-adma1759>3.0.co;2-7

Cited by 176 publications

(140 citation statements)

References 9 publications

Supporting

Mentioning

137

Contrasting

Unclassified

Order By: Relevance

“…Although the aforementioned binuclear organozirconium CGCs can achieve high levels of branching in olefin polymerization via what are clearly unusual enchainment pathways, CGCZr catalysts typically exhibit modest activities and do not generally produce high-molecular-weight polymers. In contrast, mononuclear CGCTi catalysts are known to afford high-molecular-weight polyolefins with high activity and high ␣-olefin co-enchainment efficiencies (11,12). For this reason, nuclearity effects in the Ti system were of great interest.…”

Section: Binuclear Structures and Macromolecular Branch Formation In mentioning

confidence: 99%

Nuclearity and cooperativity effects in binuclear catalysts and cocatalysts for olefin polymerization

Marks

2006

Proc. Natl. Acad. Sci. U.S.A.

223

109

View full text Add to dashboard Cite

A series of bimetallic organo-group 4 ''constrained geometry'' catalysts and binuclear bisborane and bisborate cocatalysts have been synthesized to probe catalyst center-catalyst center cooperativity effects on olefin enchainment in homogenous olefin polymerization and copolymerization processes. Significant nuclearity effects are found versus mononuclear controls, and the effect can be correlated with metal-metal approach distances and ion pairing effects. Novel polymer structures can be obtained by using such binuclear catalyst͞cocatalyst systems.catalysis ͉ polymer ͉ polyolefin E nzymes achieve superior reactivity and selectivity, in part, by their efficacy in creating high local reagent concentrations and special, conformationally advantageous active site-substrate proximities and interactions (1-4). In this regard, the possibility of unique and more efficient abiotic catalytic transformations based on cooperative effects between adjacent active centers in multinuclear transition metal complexes is currently of great interest. Within the context of the rapidly advancing and technologically significant field of homogeneous single-site olefin polymerization catalysis (5-10), the conjecture that cooperative effects involving two or more metal centers in close proximity might achieve more efficient chain propagation and͞or novel polymer architectures motivated the research that is the subject of this contribution. Single-Site Olefin Polymerization ProcessesOne of the most exciting developments in the areas of catalysis, organometallic chemistry, and polymer science in recent years has been the intense development of new polymerization technologies based on well defined single-site metallocene and coordination complex olefin polymerization catalysts (5-10). The active catalytic species is typically generated by combining a transition-metal organometallic precursor with an activator or cocatalyst. The resulting electrophilic͞coordinatively unsaturated, strongly ionpaired species then undergoes rapid olefin enchainment. In optimum cases (e.g., group 4 metal and cyclopentadienyl-type ligand), catalysts with truly exceptional productivities and selectivities for high-molecular-weight polyolefins are produced. Constrained Geometry Catalysts: Testbeds for Multinuclear Cooperativity EffectsGroup 4 ''constrained geometry'' catalysts (CGCs) (A; Fig. 1) are well known single-site polymerization agents (16, 17) that produce unusual branched, hence far more processable, polyethylenes with high productivity and selectivity. One of the key features of these catalysts is the coordinatively open nature of the active site, which allows rapid enchainment of sterically encumbered olefin comonomers into the polyethylene backbone. Under certain conditions, these catalysts yield vinyl-terminated, chain-transferred macromonomers (a macromolecule that acts as a monomer) that diffuse away and then undergo competitive reinsertion into a growing polymer chain to produce macromolecules with long chain branching (Fig. 19, which is published ...

show abstract

Section: Binuclear Structures and Macromolecular Branch Formation In mentioning

confidence: 99%

Nuclearity and cooperativity effects in binuclear catalysts and cocatalysts for olefin polymerization

Marks

2006

Proc. Natl. Acad. Sci. U.S.A.

223

109

View full text Add to dashboard Cite

show abstract

“…A family of catalysts that has been extremely successful in producing LCB-polyethylene in the solution process is called constrained geometry catalyst (CGC). [14,15] As additional advantages, CGCs are very active at the high polymerization temperatures required for the solution polymerization of ethylene and can be activated with stoichiometric amounts of borane cocatalysts in the absence of alkylaluminoxanes or alkylaluminium complexes.…”

Section: Mechanism Of Lcb Formation With Single Site Catalystsmentioning

confidence: 99%

Polyolefins with Long Chain Branches Made with Single‐Site Coordination Catalysts: A Review of Mathematical Modeling Techniques for Polymer Microstructure

Soares

2004

Macro Materials & Eng

View full text Add to dashboard Cite

Summary: Single‐site coordination polymerization catalysts are considered one of the most important developments on the technology of olefin polymerization during the last two decades. Among the several new capabilities of these catalysts is the ability to produce polymer molecules having narrow molecular weight distribution and long chain branches. These advances in polymer synthesis have stimulated the development of mathematical models to describe and predict several features of their molecular architectures. Many modeling techniques have been used for this purpose, including instantaneous distributions, population balances, the method of moments, and Monte Carlo simulations. This article reviews the mathematical models developed over the last decade to quantify the microstructure of polymers made with single‐site catalysts with special emphasis on the mechanism of long chain branch formation by terminal branching. magnified image

show abstract

“…With the homogeneous single-site catalysts, polymers of low polydispersity and uniform co-monomer composition can be readily synthesized. [1] Furthermore, with the metallocene technologies (such as Dow Chemical's Insite Technology [2] ), long chain branched (LCBed) polyethylenes, can be effectively produced through the incorporation of in situ produced or externally added macromonomers into the polymer backbone by homogeneous catalysts during ethylene polymerization. The presence of LCBs in the polymer chain can dramatically improve polymer rheological properties and enhance polymer processibility.…”

Section: Introductionmentioning

confidence: 99%

Melt Rheological Properties of Branched Polyethylenes Produced with Pd‐ and Ni–Diimine Catalysts

AlObaidi

Zhu

2004

Macro Chemistry & Physics

View full text Add to dashboard Cite

Summary: Seven branched polyethylenes differing in chain topology from hyperbranched to linear structure were synthesized with chain walking Pd‐diimine catalyst, [(ArNC(Me)C(Me)NAr) Pd(CH3)(NCMe)]SbF6 (1), and Ni‐diimine catalyst, (ArNC(An)C(An)NAr) NiBr2 (2)/MMAO, respectively. An extensive rheological study, employing steady‐shear, creep‐recovery, and dynamic oscillation tests, was conducted to examine and compare the melt rheological properties of this novel series of polymers. It was found that the change of chain topology dramatically affected the polymer flow behavior, flow activation energy, and dynamic moduli (G′(ω), G″(ω)). The hyperbranched polymers exhibited typical Newtonian flow behavior and extremely low viscosity. The polymers with chain topology intermediate between hyperbranched and linear structures, however, were essentially viscoelastic materials. All the polymers obeyed the time‐temperature superposition and exhibited enhanced flow activation energy (43.8∼57.2 kJ/mol) compared to HDPE and LLDPE. In the terminal region, these polymers had different dependencies of dynamic moduli (G′(ω), G″(ω)) on angular frequency (ω) and different master curves in the log(G′) versus log(G″) plot. The hyperbranched polymer was also blended with more linear samples as a rheology modifier and was found to significantly lower the viscosity of the blends.Structure of the Pd‐ and Ni‐catalysts used in this study.imageStructure of the Pd‐ and Ni‐catalysts used in this study.

show abstract

Materials Properties Derived from INSITE Metallocene Catalysts

Cited by 176 publications

References 9 publications

Nuclearity and cooperativity effects in binuclear catalysts and cocatalysts for olefin polymerization

Nuclearity and cooperativity effects in binuclear catalysts and cocatalysts for olefin polymerization

Polyolefins with Long Chain Branches Made with Single‐Site Coordination Catalysts: A Review of Mathematical Modeling Techniques for Polymer Microstructure

Melt Rheological Properties of Branched Polyethylenes Produced with Pd‐ and Ni–Diimine Catalysts

Contact Info

Product

Resources

About