| Polyolefin products has extensive application because of its stable physical and chemical performance, for example, polyethylene and polypropylene can be used in agriculture, construction industry, packaging industry, automobile industry, medical industry, daily life and other fields.However, there are many urgent problems to be solved at the same time. On the one hand, the production technology of synthetic resin, fiber and rubber lags behind the international level. The domestic polyolefin are mainly used as general products. Products with high value-added or high performance most still rely on imports. On the other hand, catalysts for preparation of high value-added polyolefin has been the technical barriers to restricting the development of polyolefin industry in our country. Therefore, development of novel catalyst and preparation of high-added-value products is imminent. At present, catalysts for preparation of polyolefin are mainly Ziegler - Natta catalyst, metallocene catalyst and non-metallocene catalyst. Ziegler - Natta catalyst is difficult to control the stereoselectivity because of its diversified activity center. Ziegler - Natta catalyst is more suitable for the synthesis of polyolefin with simple structure. Metallocene catalysts with single active center can control the structure of polyolefin accurately. However, the catalytic activity for olefin/polar monomer copolymerization fell sharply catalyzed by metallocene catalyst. The sensitivity of non-metallocene catalyst to heteroatomic located at polar monomer is low, so, non-metallocene catalyst can effectively catalyze the olefin/polar monomer copolymerization.Polyolefins with polar functional groups can be obtained.In this academic dissertation, 22 kinds of novel [N, P]-type early transition metal complexes were designed and synthesized. All the intermediates, ligands and complexes were characterized by NMR, EA and MS. The effect of the substituent located at silicon atoms on the synthetic reactions was not abvious, and the yield was similar. However, the change of the substituent located at aniline had larger influence on the reaction. The yield was high when fluorine atom was located at ortho and para position of aniline.Copolymerization of ethylene and propylene was catalyzed by the [N,P]-type early transition metal complexes. The results showed that when ligand contains fluorine, the catalytic activity of the complexes for copolymerization of ethylene and propylene was higher; as cyclohexyl was located at phosphorus, the catalytic activity of the complexes for copolymerization was lower, but the molecular weight of the obtained polymer was higher. We can infer that the catalytic performance was influenced obviously by electronic and space effects of the substituents in complexes.Ethylene/propylene/polar monomer terpolymerization was catalyzed by Cat.3, the optimum polymerization conditions was at a temperature of 50℃,Al/Ti mole ratio of 500 and polar comonomer concentration of 0.2 mol·L-1.Under the optimum polymerization condition, the catalytic activity for ethylene/propylene/11 -bromo-1 -undecene,ethylene/propylene/11 -chloro-1 -undecene and ethylene/propylene/9-decene-1 -alcohol terpolymerization were as high as 5.93×105, 3.12×105 and 3.11×105gP·(mol·Ti)-1·h-1, respectively. The obtained polymer had higher molecular weight. In addition, DFT calculation was used and verified the "back biting‘ in ethylene/propylene/polar monomer terpolymerization. Furthermore, the mechanical properties of polymer was characterized. The results showed that with the increase of polar monomer incorporation, the yield strength of polymer became small, which indicated that the plasticity of polymer became weak gradually.Propylene/higher α-olefin copolymerization was catalyzed by Cat. 14, the optimum polymerization conditions was determined: polymerization temperature of 50℃, Al/Zr mole ratio of 1000, higher a-olefin concentration of 0.3 mol·L-1. Under this condition, the catalytic activity for propylene/1-octene copolymer was as high as 8.76×106gP·(mol·Zr)-1·h-1. The structure and properties of the polymers were characterized by 1H NMR, 13C NMR, FT-IR, DSC, polarizing microscope and atomic force microscopy. The results showed that the copolymer chains are characterized with amorphous random soft-block segments of propylene/l-octene dispersed into hard-block segments of iPP. The hard blocks like a spring provide strength and the soft blocks provide flexibility. The various properties of the copolymers are significantly altered as a function of the incorporation percentage of l-octene into the overall structure. In addition, ethylene/propylene/ higher a-olefin terpolymer was also synthesized by Cat. 14, mechanical properties of the terpolymer is better than that of the copolymer.Supported catalyst was synthesized by loading Cat.3 onto multi-walled carbon nanotubes (Cat.3/MWCNTs). In this dissertation, polyolefin composite material with higher dielectric properties was synthesized by Cat.3/MWCNTs, the morphology of composites was coralloid which can be seen in SEM. The catalyst loaded on carbon nanotubes was through forming chemical bonds rather than the molecular inter-atomic forces between the active component and carrier, which overcame the removal of active species from carbon nanotubes in the polymerization.Based on the investigation that copolymerization catalyzed by 22 kinds of [N, P]-type early transition metal complexes with self-owned intellectual property, the optimum catalyst and the optimum polymerization conditions were confirmed. Furthermore, the relationship between the early transition metal complexes and catalytic performance, the effect of the monomer incorporation on the performance of the polymer were discussed.Ethylene/propylene/polar comonomer terpolymer with high molecular weight,propylene/higher α-olefin copolymer as thermoplastic elastomer and carbon nanotubes composite materials with higher dielectric properties were obtained. |
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