Product demands for polypropylene polymers cover a wide range of properties. Metallocene catalysts open up the way to influence the molecular properties of polypropylene by altering the ligand system of the metallocene complexes. This leads to new products with application properties which are not available with conventional catalysts. Concepts are presented to adapt metallocenes to modern, industrial polymerization processes. Some examples illustrate the particular advantages of this new generation of catalysts.

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Metallocenes offer new synthetic routes to olefin oligomers and polymers covering a wide range of molecular weights and melting points. This paper deals with some important features of the preparation of oligomers, wax‐like polymers as well as highmolecular‐weight polymers via metallocene catalysis. Taking the oligomerization of hexene as an example, a simple kinetic scheme is established, which is suitable to describe the course of the reaction and the resulting oligomer distribution with metallocenes as catalysts. For low and high‐molecular‐weight polymers, the metallocene route to polypropylene is compared to existent processes in terms of reaction conditions and product properties. An attempt is made to separate the effect of different chain defects like chain ends, regioirregularities and comonomers on the melting point.

Determination of the Chain Conformation in Fast-Spun Polypropylene Fibers by Small-Angle Neutron Scattering1In the melt spinning process filaments (fibers) are formed by extruding a polymer melt through a capillary and simultaneously applying an extensional force to the extrudate. The filaments are taken up by a winder with a constant take-up velocity. Along the spinning path the fluid extrudate is deformed, cooled, solidified, and transformed into a filament with a highly anisotropic supramolecular structure. For crystalline polymers such as polypropylene (PP), it is well-known1'3 that for sufficiently high take-up velocities, the solidification along the spinning line is due to a stress-induced crystallization process. For

The 16‐electron manganese(I) complex 1, with five ligands is astonishingly stable: It can even be handled for short periods of time in air! Crystal structure analysis of 1 establishes that the manganese has a distorted, square‐pyramidal environment.