Effect of alkylaluminum cocatalyst on ethylene polymerization with nickel-α-diimine complex

Ethylene polymerization was carried out with two nickel(II)(α-diimine) complexes: 1,4-bis(2,6-diisopropylphenyl)-acenaphthenediimine-dichloro-nickel(II) (1) and 1,4-bis(2,6-diisopropylphenyl)-ethanediimine-dichloronickel(II) (2) combined with alkylaluminum activators like methylalumoxane (MAO), trimethylaluminum (TMA), and ethylaluminum sesquichloride (EASC). The activity of these systems and the proprieties of the polymeric materials are strongly influenced by the choice of the ligand structure and, more dramatically, by the nature of the cocatalyst. EASC has been shown as giving higher productivities than TMA or MAO with both complexes, attaining 3966 kg PE/(mol Ni·h). Complex 2 gives lower productivities but produced polymers with higher polymer melting points (Tm) and crystallinity than catalyst 1.

Graphical abstractEthylene polymerization with Ni(II)-α-diimine complexes in combination with alkylaluminum activators is described. The influence of ligand structure and nature of the cocatalyst on reaction activity as well as on the properties of the polymeric material is discussed. Figure optionsDownload full-size imageDownload as PowerPoint slide