Preparation and Structure Characterization of Ethylene-Propylene Rubber-type Polymers
Late-transition metal catalysts can be applied in the polymerization of α-olefins with a unique"chain-running and chain-straightening"mechanism to produce polyolefin elastomers with special structures and excellent properties.In this study,ethylene-propylene rubber(EPR)-type polymers were prepared by polymerization of propylene with classical α-diimine nickel(Ⅱ)complexes(C1～C6)in the presence of ethylaluminum sesquichloride(EASC).The effects of catalyst dosage,n(Al)/n(Ni),propylene pressure,polymerization time,polymerization temperature,solvent,and structures of the catalysts on the polymerization were investigated systematically,and the optimal polymerization conditions were obtained.The microstructures and thermal properties of the obtained polymers were characterized by using nuclear magnetic resonance spectroscopy(NMR),infrared spectrum(IR),gel permeation chromatography(GPC),differential scanning calorimetry(DSC)and thermogravimetric analysis(TGA).The highest catalytic activity of α-diimine nickel(Ⅱ)complexes could reach 6.33× 105 g/(mol·h),the molecular weight of EPR-type polymers was in the range of 6.27×104-40.75x104 g/mol,the 1,3-enchainment content was 21％to 35％(mol),the glass transition temperature(Tg)was from-28.95 ℃ to-40.57 ℃,the decomposition temperature exceeded 400 ℃.
Late-transition metal catalystα-diimine Ni(Ⅱ)complexPropylene polymerizationEPR-type polymer
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