QUASI-LIVING CHARACTER OF ETHYLENE POLYMERIZATION BY HAFNIUM ALKOXIDE CATALYSTS

Ethylene was polymerized in the presence of soluble catalysts prepared from hafnium alkoxides and an equimolar mixture of triethylaluminium and diethylmonochloroaluminium. These systems show lower productivity than analogous systems based on titanium, but give polymer with high molecular weight, increasing with time and conversion. The kinetic analysis carried out according to the traditional steady-state kinetic model indicates the partial living character of the polymerization. This behaviour is more evident with the bidentate 1,1'-bis-2-naphtholate ligand, which further stabilizes the transition metal-carbon bond towards chain transfer.