Unsymmetrical Fluorinated α-Diimine Nickel Catalysts with Synergistic Steric and Fluorine Effects: toward Ethylene-Based Elastomers and Polar Copolymers

High Resolution Image Download MS PowerPoint Slide Polyolefin elastomers and polar-functionalized polyethylene are crucial high-performance materials, yet their synthesis is constrained by trade-offs among molecular weight, polar comonomer incorporation, and catalyst stability. To address these challenges, we developed a series of unsymmetrical α-diimine Ni(II) catalysts ( Ni1 – Ni5 ) that integrate steric shielding with a “fluorine effect.” Incorporation of a bulky dibenzhydryl substituent enhances thermal stability, while an ortho -fluorinated N -aryl unit electronically modulates the active site and suppresses chain transfer. These catalysts exhibit high activity and robustness in ethylene polymerization, affording polyethylene with high molecular weights ( M n up to 2.99 × 10 5 g·mol –1 ). Notably, the optimal catalyst further enables direct copolymerization of ethylene with long-chain ω-unsaturated alcohols and esters, yielding functionalized polyethylenes with appreciable polar comonomer incorporation. Furthermore, the resulting materials display excellent elastomeric properties, including excellent tensile strength (up to 34.6 MPa) and significantly enhanced elastic recovery (SR up to 68%), demonstrating the effectiveness of this catalyst design strategy.