Microstructure of ethylene-1-hexene and ethylene-1-octene copolymers obtained over Ziegler-Natta catalysts supported on MgCl_2(THF)_2

摘要

The ethylene copolymerizations with l-hexene or l-octene in the presence of hydrogen using three catalysts, MgCl_2(THF)_2NOCly Et_2AICl, MgCl_2(THF)fiClJEt_2AlCl, MgCl_2(THF)_2mC1JEt_2AlCl, were investigated. It was found that the addition of hydrogen into the copolymerization feed reduces the molecular weight of the copolymers produced and decreases the activity of all the studied catalysts. The microstructure of the copolymers obtained was determined on the basis of l3C NMR investigations and the reactivity ratios of the como- nomers were calculated. The lack of tendency of the olefin comonomers to the creation of the polymer block was confirmed. It was found that the products of the comonomers reactivity ratios are close to the value of 1 and they are independent of both the catalyst and comonomer type. This means that the structure of all the copolymers obtained is random.