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

摘要

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 x 10(5) 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.