The Influence of Steric Hindrance and Remote Electronic Effects on the (Co)polymerization Catalyzed by Pyridine‐Imine Nickel(II) Catalysts

ABSTRACT This study designed and synthesized a series of aniline with different steric hindrances at the ortho‐position and electron variable substituents on the diphenylmethyl group and synthesized corresponding pyridine ‐ imine ligands and nickel catalysts (Ni1‐Ni9). These nickel catalysts exhibited high activity in ethylene polymerization (up to 17.0 × 10 6 g·mol −1 ·h −1 ), producing polyethylene wax with molecular weights ranging from 5.3 × 10 3 to 12.4 × 10 3 g·mol −1 . It was found that both the ortho‐steric hindrance and remote electron effects in the ligand significantly influenced the polymerization performance. Specifically, reduced steric hindrance and the presence of electron‐withdrawing substituents at the remote position enhanced the ethylene insertion rate, whereas increased steric hindrance improved the thermal stability of the catalysts. Furthermore, these catalysts were effective in the copolymerization of ethylene with 10‐undecylenic acid, yielding polar polyethylene wax with a comonomer incorporation of 0.40 to 1.13 mol% and molecular weights of 5.7 × 10 3 to 7.2 × 10 3 g·mol −1 .