PROPYLENE POLYMERIZATION OVER PLANAR MODEL ZIEGLER-NATTA CATALYSTS: THE ROLE OF MISCELLANEOUS INTERNAL ELECTRON DONORS

An active model for a Ziegler-Natta propylene polymerization catalyst has been prepared by spin coating of a MgCl2/donor(s) solution in ethanol on a planar silica wafer, followed by crystal growth by Ostwald ripening to give well-defined MgCl2?donor(s)?nEtOH crystallites. The interaction of the internal donors with MgCl2 by spin-coating onto a silica wafer from a solution of MgCl2/ethanol containing both a diether and DIBP has been studied. When equivalent amounts of diether and DIBP were used, only 120° edge angles were formed, indicating that the diether donor is more strongly coordinated onto the MgCl2 surface than DIBP. Decreasing the amount of the diether donor resulted in no change in the morphology of MgCl2 crystallite face. When the proportion of diether donor was then further reduced; SEM images indicated, formation of 90° edge angles.