A flat model approach to Ziegler-Natta catalysts for propylene polymerization and a preparation method of well-defined crystallites of MgCl2-supported catalysts

An active model for a Ziegler-Natta propylene polymerization catalyst has been prepared by spin-coating of a MgCl2/diether donor solution in ethanol on a flat silica wafer, followed by crystal growth by Ostwald ripening to give well-defined MgCl2 center dot diether center dot nEtOH crystallites. The flat model approach facilitates detailed characterization of the catalyst and polymer using surface spectroscopy and microscopy techniques. The growth of the crystallites on the flat silica indicates formation of only 120 degrees edge angles, suggesting the preference for the formation of one particular crystallite face for the MgCl2. Subsequent treatment with TiCl4 generates the catalyst and in propylene polymerization polymer forms on the lateral face of each crystallite.