Design of Thermally Stable Amine–Imine Nickel Catalyst Precursors for Living Polymerization of Ethylene: Effect of Ligand Substituents on Catalytic Behavior and Polymer Properties

摘要

Nickel complexes bearing amine–imine ligands with various backbone substituents were synthesized and employed as ethylene polymerization catalysts on activation with Et2AlCl. The substituent on the backbone carbon atom of the amine moiety is decisive for the living nature of ethylene polymerization. A bulky amine–imine nickel precursor with a tert-butyl group on the carbon atom of the amine group can polymerize ethylene in a living fashion at an elevated temperature of 65℃, which is the highest temperature of living polymerization of ethylene with late transitionmetal catalysts. The wide applicable temperature range for living polymerization and sensitivity of the branch structure of the polyethylene to temperature enable precise synthesis of di- and triblock polyethylenes featuring different branched segments by sequential tuning of the polymerization temperature.