AM2Net Advanced Macromolecular Materials By Transition Metal Catalysis; Group 1: "New Materials by Unpolar / Polar Monomer Combinations"; Copolymer Materials of Controlled Macromolecular Architecture

• Applicant: Professor Dr. Bernhard Rieger
• Subject Area: Inorganic Molecular Chemistry - Synthesis and Characterisation
• Term: from 2002 to 2009
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5372497

The synthesis of new asymmetric "dual-side" metallocene catalysts, consisting of a combination of ethylene bridged fluorenyl-indenyl ligands, is one central topic of the present project. Based on a novel approach to indenyl fragments, bearing a variable substitution in 5,6-position, aromatic groups or even polar functionalities are introduced. It is intended to finetune the steric bulk on one side of the complexes so that coordination and insertion of higher olefin comonomers, like octene, but especially styrene and 1,4-cyclohexadiene can be controlled. New indenyl moieties from triptycene and from benzo- and dibenzo crown ethers are prepared affording zirconocene and hafnocene catalysts that bring p-electron density in close proximity to the cationic Zr(IV)-center, reducing their Lewis acidity. Consequently, other counter ions instead of B(C6F5)4- will be investigated. The benzo crown ether units allow to fix Li-cations close to the growing PP chain end, probably accelerating a reversible chain transfer between Li+ and Zr(IV). This dynamic process will be used to prepare block copolymers in the presence of propylene and styrene monomers. Finally, the application of dibenzo crown ether educts leads to bridged diindenyl ligands. Complex formation should give mononuclear of self-assembled tri- and tetranuclear catalysts with a local C2-symmetry on the Zr-centers, depending on the nature of the bridging species. The molecular catalysts and the nanoscalid mulitnuclear objects will be subjected to homo- and copolymerization reactions in our existing autoclave systems.

• DFG Programme: Research Grants