Polymerizations of butadiene with Ni(acac) 2 ‐methylaluminoxane catalysts

Polymerizations of butadiene (BD) with transition metals (MtX) and methylaluminoxane (MAO) catalysts were studied. Among the catalysts examined, nicke(II) acetylacetonate [Ni(acac) 2 ] in combination with MAO revealed the highest catalytic activities for the polymerization of BD, giving high molecular weight polymers consisting of mainly cis ‐1,4‐units in the microstructure. With Ni(acac) 2 ‐MAO catalyst, the overall activation energy for the polymerization of BD between 0°C and 60°C was estimated to be 18 kJ/mol. From a kinetic study, the rate equation for the polymerization of BD with the Ni(acac) 2 ‐MAO catalyst at 30°C can be expressed as follows: R p = [BD] 1.8 [Ni(acac) 2 ‐MAO] 0.9 . The polymerization mechanism of the polymerization of BD with the Ni(acac) 2 ‐MAO catalyst is discussed.