Lewis acids in situ modulate pyridazine-imine Ni catalysed ethylene (co)polymerisation

Abstract

Lewis acid in situ modulation plays an important role in olefin polymerisation. In this work, pyridazine-imine Ni complexes Ni1 and Ni2 have been synthesised, characterised and investigated in ethylene (co)polymerisation. In the homo-polymerisation of ethylene, the B(III) Lewis acidic additives result in increased catalytic activities (up to 19.2 × 10⁵ g mol Ni⁻¹ h⁻¹). Moreover, the B(III) Lewis acidic additives can modulate microstructures of the polyethylene products, resulting in increased branching densities and long chain branches. In the copolymerisation of ethylene with methyl 10-undecenoate, both catalytic activity and the polar monomer incorporation ratio (up to 2.0%) increased upon using B(III) Lewis acidic additives. It was indicated that the Lewis acid–base interaction between B(III) Lewis acids and the pyridazine moiety reduced the electron density from the Ni center and in situ modulated the pyridazine-imine Ni catalyzed ethylene (co)polymerisation.