Effect of Internal Electron Donors on Butadiene Polymerization Catalyzed by the TiCl4/MgCl2 Ziegler–Natta Catalyst

Ziegler–Natta (ZN) catalysts recognized as mainstream and efficient polymerization reaction catalysts are widely used for the polymerization of monolefins and diolefins due to their excellent properties. The addition of electron donors to the catalyst can effectively improve its regularity. In this article, the chelate coordination of the internal electron donors 2,3-dimethyl diethylsuccinate (DES), 2,3-diisopropyl diethylsuccinate (DIS), 2,2-dimethyl-1,3-dimethoxypropane (DMMP), and 2,2-diisopropyl-1,3-dimethoxypropane (DIMP) on the catalyst support was investigated by the density functional theory (DFT). By calculating the activation energy of the reaction before and after the addition of the internal electron donor, the effect of the internal electron donor on the stereoselectivity of the polymerization reaction was analyzed. The results indicate that all four internal electron donors can be stably adsorbed onto the support, forming closer interactions with adjacent active centers. In the butadiene insertion process, the si configuration is more favorable than the re configuration. With the addition of DES, DIS, DMMP, and DIMP, the stereoselectivity of the polymerization reaction increased from 0.7 kcal/mol on the bare active center model to 0.9, 1.2, 0.8, and 1.5 kcal/mol, respectively. Particularly noteworthy is the fact that the addition of DIMP showed the most pronounced improvement in reaction stereoselectivity.