Highly efficient incorporation of polar comonomers in copolymerizations with ethylene using iminopyridyl palladium system

Abstract

Abstract Given that high-molecular-weight functionalized polyethylene with high polar monomer incorporation ratio are often difficult to achieve, the development of highly efficient catalysts for ethylene and polar monomer copolymerization is still an urgent need in the field of olefin polymerization. In this contribution, we developed a series of highly sterically hindered iminopyridyl Pd(II) catalysts bearing the 8-aryl naphthyl substituents or/and dibenzosuberyl substituents. These substituents can provide an effective shield on the axial sites of the active center, thus allowing for the formation of high-molecular-weight polyethylene or functionalized polyethylene. Unexpectedly, these catalysts were also highly efficient for ethylene and various polar monomers copolymerization, giving access to high-molecular-weight functionalized polyethylene with very high polar monomer incorporation ratio (up to 24%). The unique structure of the iminopyridyl ligand, especially its ability to shield the axial binding sites, may lead to permitting an adequate incorporation of polar monomers in our system.