Variable Crystallinity Polyethylene Nanoparticles

Water-soluble complexes based on enolatoimine ligands bearing electron-withdrawing trifluoromethyl groups [κ²-N,O-{2,6-R₂C₆H₃NC(H)C(COCF₃)C(O)CF₃}NiMe(L)] (1a, R = 3,5-(CF₃)₂C₆H₃, L = Me(OCH₂CH₂)_nNH₂; 1b, R = 3,5-(CF₃)₂C₆H₃, L = TPPDS; 2b, R = ⁱPr, L = TPPDS; 2c, R = ⁱPr, L = TPPTS with TPPDS = PhP(p-C₆H₄SO₃Na)₂ and TPPTS = P(m-C₆H₄SO₃Na)₃) were prepared. These complexes polymerize ethylene to very small (10−30 nm) semicrystalline particles of high molecular weight (up to M_w 1.6 × 10⁶ g mol⁻¹) polymer with a degree of branching (7−63 branches per 1000 C atoms) and thus crystallinity (≤25−50%) and melt transition temperatures (T_m = 75−129 °C) variable over a large range, depending on the substituents of the N-aryl moiety (2,6-R₂C₆H₃), and the polymerization temperature. The catalysts are stable for hours under polymerization conditions (50 °C) in the highly disperse aqueous system.