High molar mass ethene/1‐olefin copolymers synthesized with acenaphthyl substituted metallocene catalysts

Abstract

The influence of ligand structure on copolymerization properties of metallocene catalysts was elucidated with three C1‐symmetric methylalumoxane (MAO) activated zirconocene dichlorides, ethylene(1‐(7, 9)‐diphenylcyclopenta‐[a]‐acenaphthadienyl‐2‐phenyl‐2‐cyclopentadienyl)ZrCl2 (1), ethylene(1‐(7, 9)‐diphenylcyclopenta‐[a]‐acenaphthadienyl‐2‐phenyl‐2‐fluorenyl)ZrCl2 (2), and ethylene(1‐(9)‐fluorenyl‐(R)1‐phenyl‐2‐(1‐indenyl)ZrCl2 (3). Polyethenes produced with 1/MAO had considerable, ca. 10% amount of trans‐vinylene end groups, resulting from the chain end isomerization prior to the chain termination. When ethene was copolymerized with 1‐hexene or 1‐hexadecene using 1/MAO, molar mass of the copolymers varied from high to moderate (531–116 kg/mol) depending on the comonomer feed. At 50% comonomer feed, ethene/1‐olefin copolymers with high hexene or hexadecene content (around 10%) were achievable. In the series of catalysts, polyethenes with highest molar mass, up to 985 kg/mol, were obtained with sterically most crowded 2/MAO, but the catalyst was only moderately active to copolymerize higher olefins. Catalyst 3/MAO produced polyethenes with extremely small amounts of trans‐vinylene end groups and relatively low molar mass 1‐hexene copolymers (from 157 to 38 kg/mol) with similar comonomer content as 1. These results indicate that the catalyst structure, which favors chain end isomerization, is also capable to produce high molar mass 1‐olefin copolymers with high comonomer content. In addition, an exceptionally strong synergetic effect of the comonomer on the polymerization activity was observed with catalyst 3/MAO. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 373–382, 2008

Kinetics and mechanism of metallocene‐catalyzed olefin polymerization: Comparison of ethylene, propylene homopolymerizations, and their copolymerization

“…The results of such comparative studies may promote our understanding on many important mechanistic problems, such as the effects of monomer type (especially ethylene vs. α‐olefins) on the formation and deactivation of metallocene catalytic species, and the nature of comonomer effects in the ethylene/α‐olefin copolymerization systems. The comonomer effects presented by metallocene catalysis systems are often more complicated than those in heterogeneous Ziegler–Natta catalysts, as the catalytic activity could be either positively or negatively changed by addition of the α‐olefin comonomer, depending on the type of metallocene complex, the comonomer structure, or the polymerization temperature . Direct determination of the active center ratio in the copolymerization system and the two related homopolymerization systems could provide us with key information for differentiating the chemical with physical natures of the comonomer effect.…”

“…The comonomer effects presented by metallocene catalysis systems are often more complicated than those in heterogeneous Ziegler-Natta catalysts, as the catalytic activity could be either positively or negatively changed by addition of the a-olefin comonomer, depending on the type of metallocene complex, the comonomer structure, or the polymerization temperature. 36,[40][41][42][43][44][45][46][47][48][49][50][51][52][53][54] Direct determination of the active center ratio in the copolymerization system and the two related homopolymerization systems could provide us with key information for differentiating the chemical with physical natures of the comonomer effect. Such studies may also help with clarifying the mechanism of forming deactivated or dormant sites in the metallocene catalysis systems as proposed in many literatures.…”

Indirect Synthesis of Bis(2‐PhInd)ZrCl2 Metallocene Catalyst, Kinetic Study and Modeling of Ethylene Polymerization

“…Electronic atmosphere of the active center in a catalyst has an important influence on the microstructures of the obtained polymer [8,9], which depends on the type of ligand, its substitutions, and bridges [10][11][12][13][14][15]. These parameters play the main role in determination of the polymer's microstructure.…”

Effect of catalyst composition on chain‐end‐group of polyethylene produced by salen‐type complexes of titanium, zirconium, and vanadium

“…However, immobilization of mentioned complexes on inorganic supports increases considerably molecular weights of produced polyethylenes (Table 1, sample 7 and 8). Because of this reason end groups could not be analyzed with the use of 1 H NMR spectroscopy, 24 and they also were practically not seen in FTIR spectra.…”