Copolymerization of propylene with 1-octene catalyzed by MgCl₂/TiCl₄/diether catalyst

MgCl₂/TiCl₄/diether is a fifth-generation Ziegler-Natta catalyst for the commercial polymerization of propylene. The outstanding features of this catalyst are the high activity and high isotacticity for propylene polymerization without using an external electron donor. In this study, we explored the copolymerization of propylene and 1-octene with MgCl₂/TiCl₄/diether catalyst. It was found that MgCl₂/TiCl₄/diether catalyst showed higher polymerization activity and led to greater 1-octene content incorporation, compared with a fourth-generation Ziegler-Natta catalyst (MgCl₂/TiCl₄/diester). With an increase in 1-octene incorporation in polypropylene chains, the melting temperature, glass transition temperature and crystallinity of the copolymers decreased distinctly. The microstructures of the copolymers were characterized using ¹³C NMR spectroscopy, and the copolymer compositions and number-average sequence lengths were calculated from the dyad concentration and distribution. This result is very important for the in-reactor polyolefin alloying process, especially for the case of a single catalyst and two-step (or two-reactor) process.