Novel tandem catalytic system of β-diketonate zirconium/two different cocatalysts for preparing branched polyethylene

Tandem catalytic systems, consisting of one catalyst with two different activators, were successfully employed in preparing branched polyethylene from ethylene as sole monomer. The catalyst precursor (β-diketonate zirconium) was used in combination with diethylaluminium chloride (AlEt2Cl) and methylaluminoxane (MAO) (or trialkylaluminum AlR3) as cocatalysts to form the oligomerization active species and copolymerization active species, respectively. The 13C NMR spectrum revealed that the resultant polymer was branched polyethylene. The molar ratio between the two cocatalysts had a remarkable effect on the catalytic activity and the properties of copolymer, such as melting temperature, crystallinity, molecular weight and molecular weight distribution.