Polymerization of trans-2-butene with (α-diimine)Ni(II) complex in combination with Et2AlCl

Polymerization of trans-2-butene with (alpha-diimine)Ni(II) complex in combination with R3Al (R = CH3, C2H5, i-C4H9), Et2AlCl, EtAlCl2 and methylaluminoxane (MAO) was investigated. Et2AlCl and EtAlCl2 as well as MAO were found to be an effective cocatalyst for the polymerization of trans-2-butene to give a high molecular weight of the polymer in good yields, but R3Al did not give any polymers. In contrast to MMAO catalyst system, a less amount of Et2AlCl to (alpha-diiminc)Ni(II) is enough to reach a high active for the polymerization, and (alpha-diimine)Ni(II)/Et2AlCl catalyst gave an optimum rate at the Al/Ni mole ratio of about 20 for the polymerization of trans-2-butene. The results obtained from a kinetic study demonstrate that the control of molecular weight is possible in the polymerization of trans-2-butene with (alpha-diimine)Ni(II)/Et2AlCl catalyst. The polymer obtained with (alpha-diimine)Ni(II)/Et2AlCl catalyst at 20 degrees C consists of -CH2-CH2-CH(CH3)- units and minor units derived from 1-butene produced by isomerization from trans-2-butene. Such minor structures can be negligible by decreasing the polymerization temperature.