Progress in the syndiotactic polymerization of styrene with metallocene/mao catalysts

Metallocene/MAO catalysts are useful for the production of syndiotactic polystyrene ‐ a new class of high performance polymers. The melting point of the obtained syndiotactic polystyrene depends on the metallocene used and can reach up to 275 °C. In the past, the most active catalysts in polymerization have been half‐sandwich titanocenes such as CpTiCl 3 and Cp*TiCl 3 . If the chlorinated compounds are changed into the fluorinated compounds as CpTiF 3 and Cp*TiF 3 , the activity increases by a factor of 5 to 100. The fluorinated titanocenes are more stable at higher temperatures and need a lower MAO excess in order to obtain optimal activities. Polymers obtained with the unsubstituted CpTiF 3 show melting points which are 17 °C lower than those synthesized by pentamethylcyclopentadienyltitaniumtrifluoride. Especially Cp*TiF 3 shows a much higher activity and, compared with the chlorinated compound, gives polymers with a higher molecular weight. Substituted cyclopentadienyltitanocenes have even higher activities. Ethene/styrene copolymers can be obtained by catalysis with zirconocene compounds.