The article describes ethylene polymerization reactions with transition metal catalysts based on complexes of CoCl_(2) and FeCl_(2) with an N,N,N-tridentate ligand 2,6-bis[1-(2,6-dimethylphenylimino)ethyl]pyridine. Th...The article describes ethylene polymerization reactions with transition metal catalysts based on complexes of CoCl_(2) and FeCl_(2) with an N,N,N-tridentate ligand 2,6-bis[1-(2,6-dimethylphenylimino)ethyl]pyridine. The complexes are converted into polymerization catalysts by reacting them either with polymethylalumoxane (MAO) or with a combination of Al(C2H5)2Cl and Mg(C4H9)2 at an [Al]:[Mg] ratio of ~3. Both MAO-activated complexes readily polymerize ethylene at 35 ℃ with the formation of linear, low molecular weight polymers with a narrow molecular weight distribution. The same complexes, when activated with the Al(C2H5)2Cl-Mg(C4H9)2 combination, form multi-center catalysts and generate polyethylenes with a broad molecular weight distribution.展开更多
Intrinsic viscosity is one of the most fundamental properties of dilute polymer solutions; its study forms an integral part of the cornerstone of the modern macromolecular theory. However, a general theory applicable ...Intrinsic viscosity is one of the most fundamental properties of dilute polymer solutions; its study forms an integral part of the cornerstone of the modern macromolecular theory. However, a general theory applicable to any chain architectures and solvent conditions has remained elusive, due to the formidable challenges in the theoretical treatment of the long-range, many-body and accumulative hydrodynamic effects. Recently, Lijia An and coworkers at the Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, has developed a new approach that largely overcomes these challenges. Their new theory provides a simple and unified theoretical framework for describing the intrinsic viscosity of polymers with arbitrary architectures under any solvent conditions and forms the theoretical basis for inferring the polymer chain structure from intrinsic viscosity measurements. Comparisons with existing experimental data yield extensive, quantitative agreement.展开更多
基金carried out according to the program of Fundamental Scientific Research of the Russian Federation
文摘The article describes ethylene polymerization reactions with transition metal catalysts based on complexes of CoCl_(2) and FeCl_(2) with an N,N,N-tridentate ligand 2,6-bis[1-(2,6-dimethylphenylimino)ethyl]pyridine. The complexes are converted into polymerization catalysts by reacting them either with polymethylalumoxane (MAO) or with a combination of Al(C2H5)2Cl and Mg(C4H9)2 at an [Al]:[Mg] ratio of ~3. Both MAO-activated complexes readily polymerize ethylene at 35 ℃ with the formation of linear, low molecular weight polymers with a narrow molecular weight distribution. The same complexes, when activated with the Al(C2H5)2Cl-Mg(C4H9)2 combination, form multi-center catalysts and generate polyethylenes with a broad molecular weight distribution.
文摘Intrinsic viscosity is one of the most fundamental properties of dilute polymer solutions; its study forms an integral part of the cornerstone of the modern macromolecular theory. However, a general theory applicable to any chain architectures and solvent conditions has remained elusive, due to the formidable challenges in the theoretical treatment of the long-range, many-body and accumulative hydrodynamic effects. Recently, Lijia An and coworkers at the Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, has developed a new approach that largely overcomes these challenges. Their new theory provides a simple and unified theoretical framework for describing the intrinsic viscosity of polymers with arbitrary architectures under any solvent conditions and forms the theoretical basis for inferring the polymer chain structure from intrinsic viscosity measurements. Comparisons with existing experimental data yield extensive, quantitative agreement.
