The π-π stacking effect of metallocene catalyst in olefin polymerization

초록

The single-sited metallocene catalyst has attracted significant attention due to its high activity and application in olefin polymerization industry. In this work, we introduced a strategy of in situ modification of metallocene catalyst with pyrene through pi-pi stacking to study the effect in olefin polymerization. After activated by MMAO, the pyrene-modified metallocene catalyst exhibited high activities (up to 1333 kg mol(-1) h(-1)) in ethylene polymerization, which was 1.9 times higher than that of the pyrene free catalyst system. This could be because the electron-donating ability of cyclopentene to the transition metal was enhanced through pi-pi interaction of pyrene with cyclopentene. The copolymerization of ethylene and 1-hexene was also studied. The pyrene-modified metallocene catalyst system performs with higher activity in the copolymerization with a lower monomer incorporation ratio. Density functional theory (DFT) calculations indicated the formation of pi-pi interaction between the Zr center with pyrene molecule leading to the increase in steric hindrance and electron density.

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