Hafnocene catalysts

Keywords Borate activation, Hafnocene catalysts, Olefin polymerization, Ultrahigh Mw polyolefins... 

In a time when prices for oil are continuously rising, hafnocene catalysts enable production of high-tech materials in a relatively cheap way. Hafnocenes are the key to a family of high and ultrahigh molecular weight polypropylenes whose material properties can be individually and simply varied. To help comprehend the importance... 

The combination of structural studies and polymerization experiments of a series of hafnocene catalysts has provided greater insight into the polymerization mechanism and the possibilities of tailoring polymer microstructures. 

Depending on the hafnocene catalyst, it is possible to obtain polypropylenes with different tacticities in a range from 10 to 80%. Taking into consideration the... 

Rieger B, Troll C, Preuschen J (2002) Ultrahigh molecular weight polypropylene elastomers by high activity dual-side hafnocene catalysts. Macromolecules 35 5742-5743... 

Rieger B, Troll C, Hild S, Cobzaru C, Deisenhofer S, Hearley A (2005) Novel high and ult-rahigh molecular weight poly(propylene) plastomers by asymmetric hafnocene catalysts. Macromol Chem Phys 206 1231-1240... 

Tilley, T. D. Woo, H.-G. Catalytic Dehydrogenative Polymerization of Silanes to Polysilanes by Zirconocene and Hafnocene Catalysts. A New polymerization Mechanism, (H. F. Harrod, R. M. Laine, Eds.) Inorganic and Organometallic Oligomers and Polymers, Kluwer Academic Publishers, Netherlands, 1991, p. 3. 

The dehydrogenating polymerization of hydrosilanes was found to be catalyzed by Group 4 metallocene alkyl and sUyl derivatives (equation 26). For zirconocene and hafnocene catalysts, the reaction was found to proceed via a-bond metathesis steps. ... 

Cobzaru, C. Deisenhofer, S. Harley, A. Troll, C. Hild, S. Rieger, B. Novel high and ultrahigh molecular weight polypropylene plastomers by asymmetric hafnocene catalysts. Macromol. Chem. Phys. 2005, 206,1231-1240. 

CATALYTIC DEHYDROGENATIVE POLYMERIZATION OF SILANES TO POLYSILANES BY ZIRCONOCENE AND HAFNOCENE CATALYSTS. A NEW POLYMERIZATION MECHANISM. 

Catalytic Dehydrogenative Polymerization of Silanes to Polysilanes by Zirconocene and Hafnocene Catalysts. A New Polymerization Mechanism. 

Among ansa-metallocene catalysts with different group IV transition metals, ansa-titanocene-based catalysts (with rare exceptions [6]) lose most of their activity above 0°C, whereas ansa-hafnocene catalysts usually give lower activities than the analogous ansa-zirconocene catalysts [7, 8], which have thus received most research interest. 

With hafnocene catalysts, higher molecular weight and slightly more stereoregular polymers were produced compared to those produced with zirconocene catalysts, although the catalytic activity was very low. 

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