Study on the microstructures of polypropylene synthesized by a novel MgCl₂-supported and low Ti-loading Ziegler-Natta catalyst

A novel MgCl₂-supported and low Ti-loading Ziegler-Natta (Z-N) catalyst was prepared by one-pot ball milling. Polypropylenes (PPs) with special microstructures were synthesized by using this catalyst. Complex gel-permeation chromatography (GPC) data of the resultant PPs were analyzed by fitting the molecular weight distribution (MWD) curves with multiple Flory-Schulz functions. ¹³C-NMR spectra of the PPs were also analyzed. A multi-site active center model and the probable structures of the active centers were proposed. Simulation of the pentad intensities of the PPs showed that the modeling results could satisfactorily account for the experimental data, which indicated that the multi-site active center model was plausible and reasonable.