Copolymerization of ethylene with 1‐hexene promoted by novel multi‐chelated non‐metallocene complexes with imine bridged imidazole ligand

Abstract

A series of novel bridged multi‐chelated non‐metallocene catalysts is synthesized by the treatment of N,N‐imidazole, N,N‐dimethylimidazole, and N,N‐benzimidazole with n‐BuLi, 2,6‐dimethylaniline, and MCl4 (M = Ti, Zr) in THF. These catalysts are used for copolymerization of ethylene with 1‐hexene after activated by methylaluminoxane (MAO). The effects of polymerization temperature, Al/M molar ratio, and pressure of monomer on ethylene copolymerization behaviors are investigated in detail. These results reveal that these catalysts are favorable for copolymerization of ethylene with 1‐hexene featured high catalytic activity and high comonomer incorporation. The copolymer is characterized by 13C NMR, WAXD, GPC, and DSC. The results confirm that the obtained copolymer features broad molecular weight distribution (MWD) about 33–35 and high 1‐hexene incorporation up to 9.2 mol %, melting temperature of the copolymer depends on the content of 1‐hexene incorporation within the copolymer chain and 1‐hexene unit in the copolymer chain isolates by ethylene units. The homopolymer of ethylene has broader MWD with 42–46. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 417–424, 2010

Ethylene/1-olefin copolymerization behaviour of vanadium and titanium complexes bearing salen-type ligand

“…1, curves 3-5) showed shoulder peaks or even bimodal shapes. That broad distributions of molecular weights had been also observed earlier for other titanium catalysts with multichelated ligands [35].…”

Preparation and characterization of polystyrene/titanium dioxide composite particles containing organic ultraviolet‐stabilizer groups

“…As shown in Table 3, with an increase of reaction temperature, the catalytic activity enhanced and reached the highest value of 1.77 × 10 4 gPE/molTi.h (run 3 in Table 3) at 50 °C and then decreased. It might attribute to that the temperature not only influences polymerization rate constant but also affects the concentration of monomer and stability of the activity center 16. As seen in Table 3, with an increase of reaction temperature from 40 to 60 °C, the MW of obtained copolymers decreased gradually and MWDs became broader slightly.…”

Copolymerization of Ethylene and Vinyl Amino Acidic Ester Catalyzed by Titanium and Zirconium Complexes

“…It might be due to the fact that temperature not only influences the chain propagation rate but also the stability of active species [19]. With an increase of temperature from 25 °C to 70 °C, the MWs of the polymers became low and the MWDs became slightly broader.…”

“…However, too high a catalyst concentration leads to fast polymer chain aggregation within the same polymerization time, it is more difficult for the monomers to approach the active centers. So either low or high catalyst concentration decreased the catalytic activity (runs [16][17][18][19] in Table 2). …”