Controlling Polar Monomer Incorporation Ratio via Steric Attenuation: Pd-Catalyzed Synthesis of Polar Hyperbranched Polyethylenes

Abstract

This study explores the synthesis of polar-functionalized hyperbranched polyethylene (HBPE) using a series of cyclohexyl-based α-diimine palladium catalysts with varying axial alkyl substituents. The catalysts were designed to investigate the influence of steric hindrance on the polymerization behavior, particularly the incorporation ratio of polar monomers such as methyl acrylate (MA). The results demonstrate that axial steric bulk significantly modulates the polymerization activity, molecular weight, and branching density of the resulting polyethylene. Notably, larger substituents led to higher activity, increased molecular weights, and reduced polar monomer incorporation, attributed to hindered coordination of bulky MA.The hyperbranched architecture of the polymers, confirmed by detailed NMR analysis, features diverse branching types with polar groups predominantly located at branch termini. This work provides a systematic approach to tailoring the properties of polar HBPE, offering insights into the steric effects of catalyst design for advanced polyolefin materials.