Heike Gregorius

Ethylene polymerization using crosslinked polystyrene as support for zirconocene dichloride/methylaluminoxane

In this paper we report on a zirconocene dichloride/methylaluminoxane catalyst system supported on a crosslinked polystyrene in order to provide ethylene polymerization catalysts for gas phase or slurry processes. Our novel approach uses the Diels-Alder reaction of cyclopentadiene functions as the final, cross-linking synthetic step. This provides polymer supported zirconocene catalysts with a homogeneous distribution of active sites. The catalysts were shown to be highly active and to form spherical beads as proven by scanning electron microscopy.

Optical studies on the intramolecular charge transfer properties of conjugated bridged donor-acceptor supermolecules

Abstract Results of optical absorption, emission experiments on conjugated bridged donor - acceptor (push - pull) molecules in different solvents are reported. Solvatochromic properties of the molecules are analysed and deviations are observed from th usual dye behaviour. By increasing the chain length of the conjugated bridge the lowest energy absorption is only slightly effected whereas the next higher energy transition shifts significantly towards lower energies. An unusual bleaching of the lowest energy absorption is observed upon illumination by UV light that recovers on a long time scale under normal conditions.