Michael Arndt-Rosenau

Copolymerization of ethene with cyclic and other sterically hindered olefins

Sterically hindered olefins like norbornene, dimethanooctahydronaphthalene (DMON), 4-methylpentene, and 3-methylbutene can be copolymerised with ethene by metallocene/MAO catalysts. Different C 2 -, C s - and C 1 -symmetric and meso-zirconocenes were used. Only isolated and alternating norbomene sequences but no norbornene blocks are formed by substituted [Me 2 C(Cp-R)(Flu)]ZrCl 2 catalysts. The alternating microstructure leads to melting points up to 270°C for ethene-norbornene copolymers and up to 380°C for the semicrystalline alternating copolymer of ethene and DMON. Other sterically hindered olefins such as 3-methylpentene build more blocky structures with high glass transition temperatures. The mechanism for the insertion reaction of the different catalysts is discussed.

Late Transition Metal Catalysts for Olefin Polymerization

The polymerization behavior of [(2-tertBuPh)2AND]NiBr2 and [(2,6-isoPr2Ph)2AND]NiBr2 activated by methylaluminoxane (MAO) and diethylaluminium chloride (DEAC) are investigated using central composite experimental designs to model response surfaces for catalytic activity and polymer properties. Beside the catalyst and experimental conditions the catalytic performance is influenced by the choice of the cocatalyst. DEAC activation yields lower catalytic activity and polymers featuring a lower molecular weight but increased branching than MAO activation.

Metallocene Catalyzed Alternating Copolymerization of Olefins

C1-symmetric metallocenes enable the production of alternating copolymers as well as that of blocky ones. A new model of copolymerization has been developed and applied to ethene/norbornene, ethene/propene and ethene/octene copolymerization. It is shown that the mechanism of polymerization depends on the catalysts structure, the monomer structure, and the temperature of polymerization.