Jochen Ebenhoch

Different surface-substituted polyorganosiloxane microgels as support materials for MAO-type cocatalysts

Twenty-five different functionalized and nonfunctionalized polyorganosiloxane microgels were applied as support materials for methylalumoxane (MAO)-type compounds to give various heterogeneous cocatalysts which are able to activate metallocene complexes like Cp2ZrCl2 for ethene polymerization. The functionalization of the microgels has a strong influence on the properties of the catalysts and the produced polyethenes.

Strain Energies of α-Alkylsubstituted Styrenes, 1,1-Di-phenyl-ethene, Tri-, and Tetra-phenyl-ethene

The standard (p° = 0.1 MPa) molar enthalpies of formation ΔfH°m (1 or cr) at the temperature T = 298.15 K were determined by using combustion calorimetry for α-ethyl-styrene (A), α-iso-propyl-styrene (B), α-tert-butyl-styrene (C), 1,1-di-phenyl-ethene (D), tri-phenyl-ethene (E), and tetra-phenyl-ethene (F). The standard molar enthalpies of vaporization ΔlgH°m or sublimation ΔcrgH°m of compounds A to F were obtained from the temperature variation of the vapor pressure measured in a flow system. Molar enthalpies of fusion ΔcrlH°m of solid compounds were measured by d.s.c. Resulting values of ΔfH°m (g) were obtained at the temperature T = 298.15 K and used to derive strain enthalpies of phenylalkenes. The interactions of the substituents are discussed in terms of deviations of ΔfH°m (g)from the group additivity rules. These values provide a further improvement on the group-contribution methodology for estimation of the thermodynamic properties of organic compounds.

Heterogeneous polymerization of ethene with metallocene catalysts. A comparison of poly(organosiloxane) microgels and silica as support materials for MAO-type cocatalysts

Zirconocene dichloride and bis(n-butylcyclopentadienyl)zirconium dichloride are used as catalyst precursors for the heterogeneous polymerization of ethene. A methyl-substituted microgel as support material for heterogeneous cocatalysts on the basis of MAO is compared with different commercially available silica-supported cocatalysts. The catalyst performances and the properties of the obtained polyethenes show considerable differences.