Mesoporous silica as nanoreactor for olefin polymerization

Various metal-containing MCM-41(Metal-MCM-41) were prepared by the post-synthesis method with organometallic compound or alkoxide and used as a nanoreactor for olefin polymerization. Strong Lewis acid sites generated on Metal-MCM-41 could activate the metallocene catalyst rac-ethylene(bisindenyl)zirconium dichloride (rac-Et(Ind)₂ZrCl₂) effectively, resulting in the formation of active sites for polymerizations of ethylene and propylene. This suggests that Metal-MCM-41 is useful as a heterogenized cocatalyst. Ti-, Zr-, Hf-, Mn- and Zn-MCM-41 combined with alkylaluminum (without metallocene catalyst) were also found to provide isotactic polypropylene with a broad molecular weight distribution. By analyzing the characteristics of polypropylenes both inside and outside the mesopores, the polymerization behavior under extreme confined geometry was discussed.