Synthesis of linear low-density polyethylene waxes through chain-walking benzocycloalkyl nickel-catalyzed ethylene polymerization

Abstract

Polyethylene wax is a highly useful material, and its diverse topological structures may have a significant impact on its applications. In this study, we have devised and synthesized a series of unilateral benzocycloalkyl α-diimine nickel catalysts. These nickel catalysts exhibited very high activities (1.06 to 10.25 × 10⁶ g mol^-1·h^-1) and yielded branched (37–97/1000 C) polyethylene waxes with low molecular weights (M_n = 0.49 to 2.01 kg mol^-1) and variable molecular weight distributions (1.79–35.05) in ethylene polymerization. Polymerization conditions such as pressure and temperature and catalyst structure such as backbone and axial substituents have an important influence on the polymerization activity and the properties of the resulting polyethylene waxes. High-temperature NMR reveals that these branched polyethylenes primarily feature short-chain branches, such as the methyl group, and exhibit a topology resembling that of low-molecular-weight linear low-density polyethylene (LLDPE).