The Investigation of Structure Performance Relationship of Dialkoxysilanes in the Initial Stage of Propylene Polymerization in the Absence/Presence of Internal Donors

摘要

Various types of alkoxysilane have been used as an external donor in propylene polymerization with MgC12-supported Ziegler-Natta catalyst. This research is to investigate the correlation between external donor structures and catalyst performance in the mechanistic way. Stopped-fiow technique was employed to obtain the direct information of active sites from the resulting polymer by temperature rising elution fractionation analysis (TREF) and density functional theory (DFT) calculations. Both internal donor-contained and internal donor-free catalyst were used to consider both direct effects and combination effects by the external donors. As results, an alkoxysilane adsorbed stronger on MgC12 surfaces tended to give a higher polymer yield. The conformation detail around active sites has played a key role of stereospecificity.