Polymerizations of ethylene and propylene using new (α-Diimine)nickel(Ⅱ) catalysts

Abstract

This thesis deals with ethylene and propylene polymerizations using new (α -diimine) nickel(II) catalysts. New unsymmetrical diimine ligands 2c-f were synthesized via sequential imination reaction from acenaphthenequinone. These new unsymmetrical α-diimine ligands were combined with nickel precursor to form new unsymmetrical (α-diimine)nickel(II) catalysts 3c-f with different ortho aryl substituents. New (α-diimine)nickel(II) catalysts were subjected to ethylene and propylene polymerizations with MAO cocatalyst. In ethylene polymerizations, new (α -diimine)nickel(II) catalyst produced a low molecular weight polyethylene. In propylene polymerizations at low temperature, the ortho aryl substituents of new (α -diimine)nickel(II) catalysts affected a tacticity of the produced polypropylene. Polypropylene produced by $C_{2v}$ -symmetric (α -diimine)nickel(II) catalysts showed a high syndiotacticity, while $C_s$ -symmetric and $C_1$ -symmetric catalysts produced a propylene with low syndiotacticity. At sub-ambient temperature, new (α-diimine)nickel(II) catalysts polymerized propylene to high molecular weight polypropylenes with narrow polydispersity. All of the (α-diimine)nickel(II) catalysts showed living polymerization behavior at sub-ambient temperature.