Flexible monoarylmethyl substituents in efficient polyethylene elastomer synthesis: facilitating chain walking and enhancing chain growth

Flexible steric strategies have proven beneficial in promoting branching formation and chain growth during α-diimine nickel-catalyzed ethylene polymerization, crucial for synthesizing polyethylene elastomer (PEE) materials. In this study, we synthesized and characterized a series of flexible monoarylmethyl α-diimine nickel catalysts. These catalysts exhibited regular activity (5.22–11.34 × 106 g/(mol Ni·h)) in PEE preparation, yielding polyethylene materials characterized by high molecular weight (263–873 kg/mol) and dense branching (35–71/1000C). Notably, compared to ethyl nickel catalyst, our monoarylmethyl nickel catalysts effectively inhibited chain transfer, resulting in PEE with molecular weights an order of magnitude higher. Additionally, when compared to the conventionally reported diphenylmethyl α-diimine nickel catalysts, our monoaryl methyl nickel catalytic system demonstrated significantly enhanced activity. Furthermore, in contrast to triaryl α-diimine nickel catalysts, our nickel system produced polyethylene with a markedly higher branching density. Testing of these PEE materials revealed excellent mechanical properties, including good elastic recovery (33–68 %), high strain (420–1230 %) and high stress (12.0–31.3 MPa) at break values. The flexible monoarylmethyl nickel catalysts demonstrated a superior activity in comparison to the traditional rigid nickel catalysts, resulting in the production of polyethylene elastomers with a significantly higher degree of branching. [Display omitted] •Successfully synthesized high-activity monoarylmethyl α-diimine nickel catalysts for PEE preparation.•Our catalysts outperform ethyl & diphenylmethyl catalysts, effectively suppressing chain transfer & showing higher activity.•PEE produced exhibits excellent mechanical properties: good elastic recovery, high strain & stress at break.