Polymerization of ethylene to branched polyethylene with silica and Merrifield resin supported nickel(II) catalysts with α-diimine ligands

Abstract

Silica and Merrifield resin were used as carriers for the support of α-diimine nickel(II) precatalysts for ethylene polymerization. The α-diimine ligands containing allyl were modified by introducing the reactive Si–Cl end-group, allowing their immobilization via a direct reaction of the Si–Cl groups with the silanols on silica surface or the hydroxyls on the ethanolamine-modified Merrifield resin. The resulting supported α-diimine ligands were characterized by analytical and spectroscopic techniques (NMR and FT-IR). The complexation reactions of the supported ligands with NiBr 2(dimethylether) (DME) gave rise to supported α-diimine nickel(II) precatalysts. These heterogeneous precatalysts exhibited high activity for ethylene polymerization in the presence of modified methylaluminoxane (MMAO) as a cocatalyst. The molecular weights of the polyethylenes obtained with the supported precatalysts were much higher than those produced with the corresponding homogeneous precatalysts.