Metallocene-catalyzed propene/1-hexene copolymerization: Influence of amount and bulkiness of cocatalyst and of solvent polarity

An investigation on the effect of the variation of the amount and the structure of cocatalyst and of polarity of the solvent on propene/l-hexene copolymerization with the isospecific catalyst rac-[ethylenebis(l-indenyl)lzirconium dichloride (rac-(EBI)ZrCl 2 ) was performed. A noticeable enhancement of copolymerization activity and a moderate increase of the molecular weights were observed with increasing MAO/Zr ratio as well as upon mixing methylaluminoxane (MAO) and AliBu 3 , while isotacticity and comonomer composition are not affected by such variations. On the other hand, a gradual increase in CH 2 Cl 2 content in the CH 2 Cl 2 /toluene solvent mixture, which greatly increases the copolymerization activity, noticeably influences the molecular weight and sensibly enhances the l-hexene comonomer content. The formation of cationic active species, separated from their counterions, might be the cause of the better accessibility of the active sites for the bulkier comonomer.