Synthesis of Bis(methoxymethyl)silanes and Their Application in MgCl2-Supported Ziegler-Natta Propylene Polymerization as External Donors

Dimethoxysilanes as external donors have been used in propylene polymerization for many years. To explore the effect of adding a carbon atom between silicon and oxygen on the performance of external donors, new bis(methoxymethyl)silane compounds including bis(methoxymethyl)diphenylsilane (Donor-PhS), diisopropylbis(methoxymethyl)silane (Donor-PS), and dicyclopentylbis(methoxymethyl)silane (Donor-DS) were first synthesized and then employed as external donors for propylene polymerization with a MgCl2-supported Ziegler-Natta catalyst. It was found that these new bis(methoxymethyl)silane external donors were conducive to improving the isotacticity of polypropylene and the catalytic activity, especially in the case of low addition. In addition, the bis(methoxymethyl)silane donors have good hydrogen regulation sensitivity. The density functional theory (DFT) calculation shows that the new bis(methoxymethyl)silanes have a wider O-1-O-2 distance and lower electron cloud density than those of dimethoxysilanes, which indicate that the external donor has better control ability on the catalyst performance at low addition.