In Silico Design of C-1- and C-s-Symmetric Fluorenyl-Based Metallocene Catalysts for the Synthesis of High-Molecular-Weight Polymers from Ethylene/Propylene Copolymerization

摘要

C-1- and C-s-symmetric fluorenyl-based metallocenes have been used extensively as catalysts for the synthesis of high-molecular-weight polymers from ethylene and propylene homopolymerization. However, these same catalysts produce only low-molecular-weight polymers in ethylene/propylene copolymerization. We have shown in a recent study that the poor performance of fluorenyl-based C-1-symmetric zirconocenes in ethylene/propylene polymerization is a result of electronic effects. Furthermore, we have also shown in another investigation that incorporating sterically demanding substituents in the 2- and 4- positions of C-2-symmetric zirconocenes can significantly increase molecular weight in copolymerization. In the present study we shall use the same approach (modifying substituents on the cyclopentadienyl and fluorenyl ligands) to design C-1- and C-s-symmetric fluorenyl-based metallocenes that afford high-molecular-weight polymers from ethylene/propylene copolymerization.