Control of Ultrahigh Molecular Weight Polypropene Microstructures via Asymmetric “Dual‐Side” Catalysts

Asymmetric ansa‐metallocene catalysts based on fluorenyl and specifically substituted indenyl ligands allow a continuous change of the properties of isotactic polypropene and thus generate a new portfolio of polypropene materials, ranging from excellent thermoplastic elastic to stiff plastomers. Controlling the length of the crystallizable, isotactic segments by means of isolated stereoerrors introduced into the isotactic enchainment made this possible. The combination of synthetic, structural and polymerization studies of a series of ansa‐asymmetric catalysts has provided much insight into the effectiveness of the substitution patterns on tailoring the polymer microstructures. Ligand substitution, temperature and concentration of the propene monomer in the reaction medium can influence stereoerrors distribution, and therefore the crystallinity of the materials. Ultrahigh molecular weight polypropenes with tacticities varying in a broad range (20% < [mmmm] < 80%) are available via (Ind‐Flu)‐based asymmetric hafnocenes.