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Macrocyclic-Constrained Bulky Binuclear Nickel Catalyst for Ethylene (Co)Polymerization
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DOI：10.1021/acscatal.6c03994.png)
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Abstract
En 中文
In nickel-catalyzed olefin (co)polymerization, simultaneously achieving high polar monomer incorporation, high molecular weight, and precise control over chain walking and branching remains a central challenge. Herein, we report an α-diimine nickel catalyst that integrates macrocyclic structural constraint, strong ortho-aryl steric shielding, and a binuclear framework. Notably, the macrocyclic ligand is readily accessible on a gram scale with good solubility. Compared with a nonmacrocyclic mononuclear analogue, this catalyst exhibits enhanced thermal stability and catalytic activity while simultaneously delivering much higher polymer molecular weights, even affording ultrahigh-molecular-weight polyethylene. Chain walking is effectively suppressed, giving low-branched polyethylene composed exclusively of methyl branches with elevated melting temperatures. Notably, both branching density and melting temperature show only weak dependence on polymerization temperature, revealing a temperature-insensitive chain-walking behavior. In ethylene–methyl undecenoate copolymerization, the catalyst shows nearly 50-fold higher activity and approximately 4-fold higher molecular weight at comparable incorporation levels. Notably, MU incorporation reaches up to 8.9% without compromising molecular weight, affording semicrystalline polar polyethylene. In contrast to ethylene polymerization, the bulky macrocyclic binuclear catalyst suppresses the 2,1-insertion/chain-straightening pathway in 1-octene polymerization, resulting in higher branching density. These results demonstrate that macrocyclic structural constraint enables the simultaneous control of chain walking and polar-monomer insertion.
Keywords:
nickel(II) catalysts
macrocyclic
α-diimine
olefin polymerization
polar-functionalized polyethylene
Journal
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13.1
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1.6W
Citations:
15.0W
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Cited Papers