The Use of Donors to Increase the Isotacticity of Polypropylene

Since the discovery of electron donors for MgCl₂-supported Ziegler–Natta catalysts, donors have become key components for improving the stereospecificity and activity of these catalysts. Starting from benzoate for third-generation catalysts, the discovery of new donor structures has always updated the performance of Ziegler–Natta catalysts. Numerous efforts have been devoted since the early 1970s, in both industry and academy, not only for discovering new donors but also for understanding their roles in Zielger–Natta olefin polymerization. This chapter reviews the history of these efforts, especially after the twenty-first century. The first half of the chapter describes the history of catalyst developments, with special focus on industrialized donors, and then introduces recent trends in the development of new donors. The second half reviews historical progress in the mechanistic understanding of how donors improve the performance of Ziegler–Natta catalysts.