Access to High-Molecular-Weight Polyethylenes through High Temperature Ethylene Polymerization Catalysed by Ethylene-Bridged ansa-(3-R-Cyclopentadienyl)(Fluorenyl) Zirconocene Complexes  

作　　者：Bo Li Haiyan Ma Jiling Huang 

机构地区：[1]Shanghai Key Laboratory of Functional Materials Chemistry and Laboratory of Organometallic Chemistry,School of Chemistry and Molecular Engineering,East China University of Science and Technology,Shanghai 200237,China

出　　处：《Chinese Journal of Polymer Science》2024年第1期42-51,I0007,共11页高分子科学（英文版）

基　　金：financially supported by the National Natural Science Foundation of China (No.21274041)。

摘　　要：A series of C1-symmetric ethylene-bridged ansa-(3-R-cyclopentadienyl)(fluorenyl) metallocene complexes(Zr: 1-5;Hf: 6) have been synthesized, characterized and investigated as catalyst precursors for the high temperature ethylene polymerization. Using methylaluminoxane(MAO) as the cocatalyst, zirconium complexes 1-5 bearing a bulky substituent on the 3-position of the cyclopendienyl ring showed high catalytic activities up to 1.48×10^(7) g PE·mol_(Zr)^(-1)·h^(-1) toward the polymerization of ethylene and afforded polyethylenes with high molecular weights(1.49×10^(5)-6.31×10^(5) g/mol), meanwhile exhibting great thermal stability at high temperatures up to 120 ℃ together with a long catalytic life time up to 2 h. By adopting low Al/Zr ratios, such as 125, polyethylenes with ultra high molecular weights up to 2.86×106 g/mol were obtained. It is worthy of noting that zirconium complexes 1-4 bearing a substituent with an aryl pendant showed temperature-dependent activities, which increased rapidly with the increase of polymerization temperature, thus weak interaction of the pendent aryl group with the cationic active center is proposed to account for the very low activities displayed at low temperatures. In contrast to zirconocene complexes 1-5, hafnocene complex 6 only displayed very low catalytic activities toward the polymerization of ethylene and afforded polyethylenes with molecular weights ten times smaller than those obtained by zirconocene complexes 1-5. Zirconocene complexes 1-5 were also able to catalyse the polymerization of propylene at high temperatures, but only afforded waxes with low molecular weights.

关 键 词：ANSA-METALLOCENE ETHYLENE Propylene Polymerization High temperature 

分 类 号：TQ325.12[化学工程—合成树脂塑料工业] TQ426