Aqueous Homo- and Copolymerization of Ethylene by Neutral Nickel(II) Complexes

Abstract

Aqueous coordination polymerization of ethylene by different neutral nickel(II) complexes [(X∧O)NiR(L)] (X ) P: type 1; X ) N: type 2) was investigated. With catalyst precursors of type 1, productivities and molecular weights were reduced by comparison to conventional polymerization in organic solvents. This effect results to a large extent from a lowering of the chain growth rate due to a low concentration of ethylene at the catalytically active centers in the aqueous polymerization. The catalysts are stable in water for hours. Stable latices of low-molecular-weight linear polyethylene were obtained with a hydrophilic complex of type 1 in an emulsion-type polymerization (Mw ca. 3 × 10 3 g mol -1 , Mw/Mn 2-3; solids content of polymer dispersions up to 10%). With complexes of type 2, productivities in aqueous ethylene polymerization were also reduced by comparison to polymerization in organic solvents. However, moderately branched semicrystalline polymers of high molecular weight are accessible (Mn > 10 4 g mol). Employing norbornene as a comonomer, high-molecular-weight amorphous copolymers were obtained in water as a reaction medium. Ethylene solubility in water-acetone mixtures was estimated experimentally.

Characterization of conductive multiwall carbon nanotube/polystyrene composites prepared by latex technology

“…Application of latex technology is a relatively new approach to incorporate CNTs inside any kind of highly viscous polymers, which can be synthesized by emulsion polymerization such as polystyrene (PS), PMMA and polyethylene [30,31], or which can be brought into artificial latex (e.g. by applying high shear conditions) [26].…”

Synthesis of Very Small Polymer Particles by Catalytic Polymerization in Aqueous Systems

“…Two types of catalyst system have emerged for ethylene polymerization in aqueous systems, nickel(II)phosphinoenolate complexes [10][11][12][13][14][15] (1) and nickel(II) salicylaldiminato complexes [12,16,17] (2). Both types of catalysts had originally been developed for non-aqueous polymerizations.…”

“…[17] Copolymerization is an alternative for crystallinity control independent of molecular weight. [12,24] Both types of catalyst can be active in aqueous emulsion polymerization for hours.…”

Titanium (IV) and Nickel (II) Catalysts Based on Anilinotropone Ligands

“…(3) Many late-metal catalysts are compatible with protic solvents and nucleophilic impurities. Water compatibility has led to successful emulsion polymerization of ethylene [43][44][45][46]. (4) Expanded functional group tolerance has permitted the copolymerization of alkyl acrylates (polar monomers) with ethylene andolefins (non polar monomers) [47][48][49][50].…”