Hydrogen‐Bonding‐Induced Heterogenization of Nickel and Palladium Catalysts for Copolymerization of Ethylene with Polar Monomers

Abstract

The practical synthesis of polar-functionalized polyolefins using transition-metal-catalyzed copolymerization of olefins with polar monomers is a challenge; the use of heterogeneous catalysts is little explored. Herein, we report the synthesis of heterogeneous naphthoquinone-based nickel (Ni/ SiO 2 ) and palladium (Pd/SiO 2 ) catalysts through hydrogen bonding interactions of the ligands with the silica surface. Ni/ SiO 2 exhibits high activities (up to 2.65 10 6 g mol À1 h À1 ) during the copolymerization of ethylene with 5-hexene-1-ylacetate, affording high-molecular-weight (M n up to 630 000) polar-functionalized semicrystalline polyethylene (comonomer incorporation up to 2.8 mol %), along with great morphology control. The resulting copolymers possess improved surface properties and great mechanical properties. Pd/SiO 2 can mediate ethylene copolymerization with polar monomers with moderate activity to produce high-molecular-weight copolymers with tunable comonomer incorporation.Scheme 1. Plausible heterogenization approaches for olefin polymerization catalysts.

A general strategy for heterogenizing olefin polymerization catalysts and the synthesis of polyolefins and composites

“…Cai and coworkers prepared a heterogeneous system through the reaction of an anilinonaphthoquinone nickel complex with methylaluminoxane (100 equiv.) modified silica (MMAO/SiO 2 ), which could copolymerize ethylene with 5-hexene-1-yl acetate and allyl acetate 39 , 40 .…”

A Heterogeneous Palladium Catalyst for the Polymerization of Olefins Prepared by Halide Abstraction Using Surface R3Si+ Species

“…Anilinonapthoquinone Pd‐complexes adsorb onto silica by forming hydrogen bonds between surface silanols and the distal carbonyl of the functionalized quinone ligand. The distribution of Pd sites copolymerize ethylene and methylacrylate to form polymers with broad molecular weight distributions ( Đ = M w / M n =3.9) [10] . Heterogeneous derivatives of Brookhart's [(α‐diimine)Pd−CH 3 ] + catalyst [6c] are available from the reaction of (α‐diimine)Pd(CH 3 ) 2 with sulfated zirconium oxide, an established weakly coordinating support, [11] to form palladium sites that produce narrow molecular weight distributions of polymers ( Đ =1.4–1.9), though only ≈9 % of the Pd sites are active from 2 H labelling studies [12] .…”

Trifluoromethoxy-substituted nickel catalysts for producing highly branched polyethylenes: impact of solvent, activator andN,N′-ligand on polymer properties

“…1–4 Of particular note is the ability of these catalysts to promote the displacement of the metal center along the growing polymer chain by a process commonly termed “chain walking”. 5 Indeed, the resulting branched polymeric materials display a wide range of promising properties. In the past two decades, great progress has been made in rationalizing the relationship between the chelating ligand and catalytic activity and polymer microstructure, with the result that different chain architectures and topologies ranging from semicrystalline plastic, through to highly branched thermoplastic elastomers to waxes or oils are all accesssible.…”