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
Valley,as a new degree of freedom for electrons,has drawn considerable attention due to its significant potential for encoding and storing information.Lifting the energy degeneracy to achieve valley polarization is ne...Valley,as a new degree of freedom for electrons,has drawn considerable attention due to its significant potential for encoding and storing information.Lifting the energy degeneracy to achieve valley polarization is necessary for realizing valleytronic devices.Here,on the basis of first-principles calculations,we show that single-layer FeCl_(2)exhibits a large spontaneous valley polarization(∼101 meV)arising from the broken time-reversal symmetry and spin-orbital coupling,which can be continuously tuned by varying the direction of magnetic crystalline.By employing the perturbation theory,the underlying physical mechanism is unveiled.Moreover,the coupling between valley degree of freedom and ferromagnetic order could generate a spin-and valley-polarized anomalous Hall current in the presence of the in-plane electric field,facilitating its experimental exploration and practical applications.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.
基金This work is supported by the National Natural Science Foundation of China(No.11804190)Shandong Provincial Natural Science Founda-tion of China(Nos.ZR2019QA011 and ZR2019MEM013)Qilu Young Scholar Program of Shandong University,and Taishan Scholar Program of Shandong Province,and Youth Science and Technology Talents En-rollment Project of Shandong Province.
文摘Valley,as a new degree of freedom for electrons,has drawn considerable attention due to its significant potential for encoding and storing information.Lifting the energy degeneracy to achieve valley polarization is necessary for realizing valleytronic devices.Here,on the basis of first-principles calculations,we show that single-layer FeCl_(2)exhibits a large spontaneous valley polarization(∼101 meV)arising from the broken time-reversal symmetry and spin-orbital coupling,which can be continuously tuned by varying the direction of magnetic crystalline.By employing the perturbation theory,the underlying physical mechanism is unveiled.Moreover,the coupling between valley degree of freedom and ferromagnetic order could generate a spin-and valley-polarized anomalous Hall current in the presence of the in-plane electric field,facilitating its experimental exploration and practical applications.
