Recent Advances in Coordination–Insertion Copolymerization of Ethylene with Polar Monomers Catalyzed with Pd and Ni Complexes

The incorporation of polar functional groups into polyethylene (PE) chains at controlled concentrations enables tailored multi-functionality, manifesting as printability enhancement, improved dyeability, and enhanced blending compatibility with diverse polymeric materials. The most effective way to incorporate polar monomers into the PE macromolecules is the transition metal-mediated coordination–insertion copolymerization of ethylene with polar monomers. However, the Lewis basic heteroatoms (N, O, S, P, etc.) in polar monomers are prone to strongly coordinate to the catalytic center, resulting in irreversible catalyst deactivation. Owing to the nature of tolerance to Lewis basic functionalities, rationally designed Pd and Ni complexes have proven to catalyze direct coordination polymerization of ethylene with polar monomers, which opened a practical way to prepare functionalized polyethylenes (F-PEs). In this context, we summarize the recent advances of the Pd and Ni complexes catalyzed copolymerization of ethylene with various polar monomers, especially focused on those commercial polar monomer feedstocks. In addition, the effects of metal, ligand structural modification, and additives regulation on the catalytic performances were analyzed in detail. Some key ideas on the salient aspects of the catalyst are presented, and the challenges and prospects of Pd and Ni catalysts in the polar monomer copolymerization problems are also discussed.