Highly Linear And Hyperbranched Polyethylene Produced By Late Transition Metal(Ni,Fe,Co) Complexes Through Coordination Catalytic Polymerization

This dissertation focuses on the design and synthesis of new nickel pyridinimide catalytic system and diiminopyridine iron and cobalt catalytic system,and their application in the improvement of catalytic activity and thermostability for ethylene polymerization to prepare hyperbranched polyethylene and high linear polyethylene.As well as the exploration of the effect of reaction temperature,reaction time,ethylene feed pressure and the ratio of Al/M on polymerization performance.Four parts are included in this thesis as follow:Part ?:The background of application status and prospect of polyethylene and polyolefin as well as the research progress of olefin polymerization catalysts are reviewed here,the development of two kinds of catalytic systems for late-transition metal complexes is introduced in detail.The significance of this research is discussed.Part ?:A series of 8-?4-R-2,6-dibenzhydrylphenylimino?-5,6,7-trihydroquinolines ligands and the corresponding nickel complexes were prepared and characterized by ¹H and ¹³C NMR,FT-IR,elemental analysis,and the single-crystal X-ray diffraction.By using modified methylaluminoxane?MMAO?or diethylaluminum chloride?Et₂Al Cl?as the cocatalysts,all nickel pre-catalysts exhibited good activities toward ethylene polymerization,producing hyperbranched unsaturated polyethylene waxes-oil?up to 157 branches/1000C?,with low molecular weights and narrow polydispersity.Part ?:A series of 2-?1-arylimino?ethyl-9-arylimino-5,6,7,8-tetrahydrocyclohepta-pyridine ligands and the corresponding cobalt and iron complexes were prepared and characterized by ¹H and ¹³C NMR,FT-IR,elemental analysis,and the single-crystal X-ray diffraction.On treatment with either methylaluminoxane?MAO?or MMAO,all the cobalt pre-catalysts exhibited high activities toward ethylene polymerization with the production of high linear unsaturated polyethylene.Part ?:Summary and give a brief overview on the conclusions of this thesis,the development of ethylene polymerization and its catalysts combined with the current research progress are prospected.