Classical polymers like polyolefins, polystyrene have still many fundamental questions yet to be answered and many problems are unsolved. In particular, the control of morphologies in hybrid systems of inorganic/organic and organic/organic materials is one of the major challenges. We focused strongly on polyolefins, which are mainly synthesized by supported catalysts based on metallocenes or Ziegler-Natta systems. The supports play a decisive role in the control of the activity of the catalysts and the product properties, as the spherical shape of the support is replicated in the product and is of particular importance for processing. We have demonstrated previously that the inorganic supports can be easily replaced by organic particles obtained by emulsion polymerization and can be surface functionalized in a wide variety in such a way that they can immobilize almost all common olefin polymerization catalysts. Following this strategy, polyolefins with narrower molecular weight distributions have been obtained compared to the application of common inorganic supports. This behavior indicates that due to the smooth surface, more uniform catalytic sites are formed. The obtained PDI range between 3 and 5 and polyolefins produced by different metallocenes must be blended to reach such values. Particles of an unprecedented spherical shape are accessible by using systems wherein the catalysts are immobilized inside of hollow spheres. We even succeeded to support Ziegler-Natta and metallocenes simultaneously on organic and inorganic hybrids supports with high spatial resolution. Due to replication of the structure of the catalyst system this technique results in core-shell structures of different types of polyolefins such as linear low density polyethylene LLDPE and high density polyethylene (HDPE).
In view of the development of the hollow sphere based catalyst systems, we will now be able to tackle one of the most critical questions, which is the sensitivity of the polymerization catalysts towards impurities. Polar compounds, which lower the catalyst activity, would not be able to pass the surrounding shell. Due to such a membrane behavior of a support, the activity of catalytic could be enhanced and the polymerization dramatically facilitated.