13C NMR analysis of α-olefins copolymers with 1,3-butadiene obtained with zirconocenes/methylalumoxane catalysts

Ethylene copolymers with propene and/or 1,3-butadiene were obtained using bis(η⁵-cyclopentadienyl)zirconium dichloride ( 1 ) or ethylenebis[1-3a, 7a-η-(4,5,6,7-tetrahydro)-1-indenyl]zirconium dichloride ( 2 ) and methylalumoxane as catalytic systems. A detailed ¹³C NMR analysis of the copolymers was performed. The resonances in the olefinic region of the terpolymers were assigned to ethylene/butadiene/ethylene and propene/butadiene/ethylene sequences while the butadiene/propene sequence was ruled out. Analogously, no polymers were obtained from the polymerization of propene in the presence of 1,3-butadiene. It is thus shown that the conjugated diene is an inhibitor for the polymerization of α-olefins. The presence of trans-1,2-cyclopentane rings was detected both in the ethylene/butadiene copolymers and in the ethylene/propene/butadiene terpolymers. A different behaviour of the two catalysts was observed.