The discovery and evolution of metallocene-based olefin polymerization catalysts

The development of the homogeneous metallocene/methylaluminoxane catalyst for the polymerization of olefin has widely increased the possibilities in controlling the polymer composition, polymer structure, tacticity and special properties with high precision compared to the heterogeneous Ziegler–Natta and Phillips catalysts. Metallocene catalysts allow the synthesis of isotactic, isoblock, syndiotactic, stereoblock or atactic polymers, as well as polyolefin composite materials with superior properties and low content of extractables. The homogeneous character of metallocene-based catalysts leads to a better understanding of the mechanism of the olefin polymerization and allows the synthesis of optically active olefin oligomers using chiral transition metal complexes. These single-site catalysts are able to copolymerize ethene and propene with short- and long-chained α-olefins, cyclic olefins, or polar vinyl monomers such as ethers, alcohols or esters. Such copolymers are suitable for blends of polyolefins with polyethers and other polar polymers because of an excellent adhesion of the two polymers. In the future, polyolefin nanocomposites and tailored copolymers open up the approach to new classes of materials with great property combinations such as improved stiffness, high gas barrier properties, significant flame retardancy, and high crystallization rates.