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Variable Crystallinity Polyethylene Nanoparticles

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journal contribution
posted on 09.06.2009, 00:00 authored by Sze-Man Yu, Stefan Mecking
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 Mw 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 (Tm = 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.