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Metallocenes and other transition metal complexes, activated by methylaluminoxane allow the synthesis of polyolefins with a highly defined microstructure, tacticity, and stereoregularity. New copolymers, long chain branched polymers, and polyolefin nanocomposites are produced by these highly active catalysts. A better understanding of the structure of active sites for the olefin polymerization will lead to findings of new and simpler co-catalysts. Ethene or propene can be copolymerized with 1-olefin macromers with chain lengths up to 12,000 g mol(-1) as well as with cyclic olefins. Polypropenes of high molecular weight and filled with multi-walled carbon nanotubes show exciting new physical and mechanical properties and are prepared by in situ polymerization. These, and other polyolefin specialities, will be new future materials in a wide range of applications.

Polyolefins belong to the most non-polluting mass polymers since they consist of carbon and hydrogen, only. Additionally the pure polymers can be easily reused, they can be decomposed into their monomer building blocks or they can be burned to carbon dioxide and water under production of energy. With metallocene catalysts the efficiency of the polymerization compared to the common "Ziegler-Natta" catalysts can be increased by the factor of 10-100. Therefore, resources are saved and energy costs decreased. The metallocene catalysts allow in a so far unknown fashion the synthesis of polymers in a very distinctive way. By variation of the ligand structure it is possible to influence as well the microstructure of the polymers as the stereo- and regio-selectivity and the tacticity in a broad range. Therefore, the production of polymers with outstanding mechanical properties becomes possible, so far these were reserved for high-performance polymers, which can be only made with high efforts and less environmentally compatible.

This paper shows the capability and advantage of the in-situ polymerization of olefins as a technique for the preparation of nanocomposites. The nanocomposites base on high molecular weight and highly isotactic polypropylenes and oxidized multi-walled carbon nanotubes (HMWiPP/MWCNT). Since a good interfacial adhesion between the matrix and the filler is crucial for the successful preparation of nanocomposites the polymerizations were performed with MAO anchored covalently to the surface of the nanotubes. Thus, a heterogeneous co-catalyst is formed and the polymerization starts directly on the tube surface. The resulting nanocomposites contain 0.9–25 wt% multi-walled carbon nanotubes and polypropylene with a molecular weight of about 1.4 × 106 g/mol. They were investigated with respect to their properties, like crystallization and melting temperature, as well as half-time of crystallization which decreases very strong in dependence on a rising filler content. The morphology analysis shows a homogeneous CNT distribution, a good separation of the individual particles, a very good interfacial adhesion and that every nanotube is covered by a thin polymer layer. [ABSTRACT FROM AUTHOR]

This paper reviews investigations into the composition of macro- and microcrystalline paraffin waxes, focused on the structure of these paraffin waxes. This paper describes a analytical method that gives massive information about the structure of the paraffin waxes, using a special 13 C-NMR spectroscopy method. This method based on a characterization of ethene/a-olefine copolymers that exhibit a similar structure to that of paraffin waxes. [ABSTRACT FROM AUTHOR]