Living Aqueous Microemulsion Polymerization of Ethylene with Robust Ni(II) Phosphinophenolato Catalysts.

Due to chain transfer events being competitive with chain growth, ethylene polymerization by P,O-chelated Ni(II) complexes usually affords low molecular weight polymers or oligomers. We now show that appropriately bulky substituted phosphinophenolato Ni(II) can polymerize in a living fashion, virtually devoid of chain transfer. Aqueous polymerizations with microemulsions of [κ2-P,O-2-(2-(2',6'-(MeO)2C6H3)C6H4)(Ph)P-6-(3',5'-(CF3)2C6H3)C6H3O-NiMe(pyridine)] (3) at 30 °C yield polyethylenes with narrow molecular weight distributions (Mw/Mn 1.02 to 1.34) and ultrahigh molecular weights (up to 2 × 106) in the form of aqueous nanoparticle dispersions. Catalyst stability and activity are maintained up to 70 °C in water.