Catalysts For Copolymerization Of Ethylene Research Articles

Bidentate Pyridyl‐Amido Hafnium Catalysts for Copolymerization of Ethylene with 1‐Octene and Norbornene

AbstractPolyolefin elastomers (POEs) and cyclic olefin copolymers (COCs) are high‐performance polyolefin materials of wide interest. It is crucial to develop low‐cost and high‐performance transition metal catalysts to prepare these polyolefin materials. In this contribution, we designed and synthesized a series of bidentate pyridyl‐amido hafnium catalysts and used them in ethylene polymerization and copolymerization with comonomers including 1‐octene and norbornene. These catalysts exhibited high activities of up to 16.3×106 g mol−1 h−1 and produced polyethylene with a high molecular weight of up to 24.5×104 g mol−1 in ethylene polymerization at 150 °C. More importantly, these catalysts produced ethylene/1‐octene copolymers with incorporation of up to 13.7 mol % and molecular weight of up to 72.7×104 g mol−1, and prepared ethylene/norbornene copolymers with incorporation of up to 50.3 mol %, along with glass transition temperature of up to 184.3 °C and molecular weight of up to 187.6×104 g mol−1. The ease of synthesis, high versatility and great copolymerization properties of these hafnium catalysts make them highly attractive for future studies.

Design and synthesis of binuclear vanadium catalysts for copolymerization of ethylene and polar monomers

Binuclear vanadium complexes exhibited higher activity than monometallic complexes in ethylene polymerization and afforded UHMWPE. The binuclear catalysts also showed moderate activity in copolymerization with 10-undecen-1-ol and methyl 10-undecenoate.

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

AbstractThe 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/SiO2) and palladium (Pd/SiO2) catalysts through hydrogen bonding interactions of the ligands with the silica surface. Ni/SiO2 exhibits high activities (up to 2.65×106 g mol−1 h−1) during the copolymerization of ethylene with 5‐hexene‐1‐yl‐acetate, affording high‐molecular‐weight (Mn 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/SiO2 can mediate ethylene copolymerization with polar monomers with moderate activity to produce high‐molecular‐weight copolymers with tunable comonomer incorporation.

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

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/SiO2 ) and palladium (Pd/SiO2 ) catalysts through hydrogen bonding interactions of the ligands with the silica surface. Ni/SiO2 exhibits high activities (up to 2.65×106 g mol-1 h-1 ) during the copolymerization of ethylene with 5-hexene-1-yl-acetate, affording high-molecular-weight (Mn 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/SiO2 can mediate ethylene copolymerization with polar monomers with moderate activity to produce high-molecular-weight copolymers with tunable comonomer incorporation.

Double-Decker-Type Dipalladium Catalysts for Copolymerization of Ethylene with Acrylic Anhydride

Dipalladium complex with a macrocyclic ligand having two diimine sites catalyzes copolymerization of ethylene with acrylic anhydride to afford the copolymer containing the repeating unit from acrylic anhydride. The obtained copolymer contains the cyclic and acyclic anhydride groups in high content (up to 5.7 mol %) in the main chain. It is contrasted with that the monopalladium complex with the diimine ligand catalyzes the reaction to yield the copolymer having the polar group at the end of branches with lower content (0.8 mol %). Decreased ethylene pressure of the reaction using the dipalladium catalyst results in increase in the polar comonomer unit content. Methanolysis of the copolymer takes place smoothly to give the polymer with both carboxylic acid and ester groups in the polymer chain.

Robust Bulky [P,O] Neutral Nickel Catalysts for Copolymerization of Ethylene with Polar Vinyl Monomers

Several nickel complexes bearing sterically bulky phosphino-phenolate ([P,O]) ligands were synthesized and explored as catalysts for olefin (co)polymerization. In the absence of an activator, the complexes showed very high catalytic activities (up to 107 g molNi–1 h–1) for ethylene polymerization even at 90 °C or with the addition of a large amount of a polar additive (such as ethyl alcohol, diethyl ether, acetone, or even water), affording linear polymers with high molecular weights (up to 6.53 × 105). In contrast, most of the previously reported nickel catalysts suffer from severe activity suppression at elevated temperature. It is rare that a catalyst has so many good performances simultaneously, including high catalytic activity, good tolerance for polar groups, strong thermal stability, and yielding high molecular weight linear polyethylene. Most importantly, these bulky nickel complexes used in this study also effectively copolymerized ethylene with challenging polar vinyl monomers, including commer...

Use of Vanadium Complexes Bearing Naphthalene-Bridged Nitrogen-Sulfonate Ligands as Catalysts for Copolymerization of Ethylene and Propylene.

Vanadium complexes bearing naphthalene-bridged nitrogen-sulfonate ligand ([ê2(N,O)-8-(PhN)-1-naphthalenesulfonato]VOCl (1a) and [ê2(N,O)-8-(PhN)-1-naphthalenesulfonato]VCl2 (1b)) were synthesized. Activated by ethylaluminium sesquichloride (EASC) and in the presence of ethyl trichloroacetate (ETCA) as reactivator, complexes 1a and 1b showed activities of up to 39.1 kg polymer (mol V)−1 h−1, affording the copolymers with high molecular weights (Mw up to 28 × 104) and narrow molecular weight distributions (Mw/Mn ~ 3.0) as well as high propylene incorporation of up to 49.4%. Compared to the traditional VOCl3 system, these complexes exhibited higher propylene incorporation ability and higher catalytic activities especially at high polymerization temperatures of 50 °C and above. Determined by DSC and 13C NMR, the copolymers obtained with 1a and 1b had more random structures than that with the VOCl3 system.

Nickel Catalyzed Copolymerization of Ethylene and Alkyl Acrylates.

Ni(II) complexes bearing an o-bis(aryl)phosphinophenolate ligand were synthesized as catalysts for copolymerization of ethylene and alkyl acrylates. When the P-bound aryl group was 2,6-dimethoxyphenyl group, one of the oxygen atoms in the methoxy groups coordinated to the nickel center on its apical position. This complex was a highly active catalyst without any activators to give highly linear and high molecular weight copolymers. The structures of the copolymers were determined by 1H and 13C NMR to clarify that the alkyl acrylate comonomers were incorporated in the main chain and that the structures of the copolymers were significantly influenced by the structure of the aryl group in the ligand.

Synthesis and catalytic activity of camphor titanium complexes

Three new camphor–titanium complexes [TiClCp2L] (L=1L, (1); 2L, (2) and 3LH (3)) were obtained through replacement of one chloride by a camphor-type ligand (1LH, 2LH, 3LH2 (3)) at the coordination sphere of [TiCl2Cp2]. Complexes 1 and 2 were structurally characterized by X-ray diffraction analysis showing that coordination occurs through the oxygen atom of the hydroxo group (1) with cooperative coordination of the nitrogen atom of the oxime complex in 2. Upon activation with MAO complexes 1 and 2 promote ethylene polymerization and ethylene/norbornene co-polymerization while compound 3 displays no catalytic activity for either one or the other process. At 50°C the catalytic activity complex of 2 (852kgPEmol−1h−1) for ethylene polymerization is higher than that of compound 1 (668kgPEmol−1h−1) which is similar to that of [TiCl2Cp2] (670kgPEmol−1h−1). The catalytic activity of complex 1 displays a higher dependence on the temperature than that of compound 2 which is attributed to the strength of the Ti–O bond that renders generation of the active site more difficult in 1. Compounds 1 and 2 are also active catalysts for co-polymerization of ethylene with norbornene affording copolymers with approximately 15mol% of norbornene content.The microstructures of the polyethylenes and ethylene norbornene co-polymers were checked by NMR and their melting points were measured by DSC.

Combinatorial Synthesis and Evaluation of α-Iminocarboxamide-Nickel(II) Catalysts for the Copolymerization of Ethylene and a Polar Monomer

Late-transition metal catalysts used for olefin polymerization, the so-called postmetallocenes, which includes α-iminocarboxamide-nickel(II) catalysts have attracted a great deal of attention because of many valuable features such as the copolymerization of α-olefins with polar monomers. In this paper, the combinatorial synthesis and evaluation of α-iminocarboxamide-nickel(II) catalysts are discussed for their roles in the discovery of a highly active catalyst and elucidation of its structure-activity relationship. The combinatorial optimization of each reaction condition was performed, then a combinatorial library of α-iminocarboxamides with systematically modified substituents was constructed by amidation of α-keto acid chlorides and subsequent imination of α-keto carboxamides in parallel fashion. As a result, 87 analytically pure α-iminocarboxamide ligands were successfully synthesized. α-Iminocarboxamide-nickel(II) catalysts were prepared from the synthesized α-iminocarboxamide ligands. The catalysts' activities for polymerization of ethylene and copolymerization of ethylene and 5-norbornen-2-ol were evaluated. Results of the present study revealed 9 novel active catalysts for ethylene polymerization and 7 novel active catalysts for copolymerization of ethylene and 5-norbornen-2-ol. It should be noted that the best catalysts for ethylene polymerization and for copolymerization in the present study showed higher activities compared to the known active catalyst. Polymerization activities of the catalysts varied dramatically according to the combination of substituents on the α-iminocarboxamides.

With different structure ligands heterogeneous Ziegler–Natta catalysts for the preparation of copolymer of ethylene and 1-octene with high comonomer incorporation

Comparison with the conventional Ziegler–Natta catalyst TiCl4/MgCl2 (I), the modified supported Ziegler–Natta catalysts (iso-PentylO)TiCl3/MgCl2 (II) and (BzO)TiCl3/MgCl2 (III) were prepared as efficient catalysts for copolymerization of ethylene with 1-octene. The complexes (II) and (III) were desirable for the production of random ethylene/1-octene copolymers coupled with higher molecular weight, higher comonomer incorporation within copolymer chain and good yield even at high temperature 80 °C and fairly low Al/Ti molar ratio of 100. The effects of catalysts ligands, Al/Ti molar ratio, polymerization temperature, as well as concentration of 1-octene on the catalytic activity, molecular weight and microstructure of the copolymer were investigated in detail. The structure and properties of the copolymers were characterized with 13C NMR, GPC, DSC and WAXD. The kinetic results also indicate that these catalysts (II) and (III) show higher catalytic activity and the produced polymers feature higher molecular weight, because of lower ratio of Ktrm/Kp and Ktra/Kp, and higher ratio of Ktra/Ktrm which indicates that chain transfer to cocatalyst is predominant.

Studies on probing SiO2 surface using BF3 as probe and SiO2/Al2Et3Cl3/TiCl4(PhMgCl) catalytic system for copolymerization of ethylene and propylene

Using BF 3 as probe, the surface of SiO 2 was probed. The effects of the roast temperature on the SiO 2 surface were investigated and a possible mechanism is suggested. Using SiO 2 as starting material for supports, new supported catalysts for copolymerization of ethylene and propylene were prepared and their possible structures are discussed. It was found that higher polymerization productivity, for instance, 480 kg P/mol Ti h, can be obtained by using a SiO 2 /Al 2 Et 3 Cl 3 /TiCl 4 catalytic system and addition of PhMgCl to this catalytic system can significantly increase polymerization activity.