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摘要
Two C-s- and C-1-symmetric doubly hetero-bridged metallocene complexes (Me2C) (Me2Si) - Cp2TiCl2, (1) and [(CH2)(5)C] (Me2Si) Cp2TiCl2 (2) were used in the propylene polymerization under the activation of MAO. The reaction parameters, such as reaction temperature, Al/Ti molar ratio and reaction time were employed in order to study the influences on the polymeration activity and the structures of the resulting polymers. The microstructure, thermodynamic properties, molecular weight and molecular weight distribution of the resulting polymers were characterized by C-13-NMR, DSC and GPC. The catalytic activity of the two complexes was up to 10(6) gPP/mol.h. The high molecular weight and narrow weight distribution polymers (M-w up to 7 x 10(5), MWD about 2. 0) were prepared at 0. 1 MPa propylene pressure. The two metallocenes exhibit good catalytic performance at low polymerization temperatures. The polymerization activity and molecular weight decrease with the increase of polymerization temperature. The polymerization activity and molecular weight of polymers showed the trend of increase and then decrease with the Al/Zr molar ratio increase. The results indicated that the resulting polymer was atactic polypropylene with high molecular weight by C-13-NMR and DSC analysis. It was found that the two different shortest bridges, unusually large dihedral angle of two Cp (71. 0 degrees,70. 3 degrees), show obvious influence on the catalytic properties and behavior of polymers.
- 出版日期2016-1-20
- 单位河北工业大学
