Atom transfer radical polymerization (ATRP) with concurrent reverse and normal initiation process was investigated. Bulk polymerizations of both n-butyl acrylate (BA) and styrene (St) were conducted using CuBr2 complexed with 1 equiv of tris(2-(dimethylamino)ethyl)amine (Me6-TREN) as the catalytic system, initiated by 2,2′-azobis(isobutyronitrile) (AIBN) and an alkyl halide (RX). Polymerization of BA at 60 or 90°C provided well-defined polymers with molecular weights up to 40 000 g/mol and low polydispersities (Mw/Mn < 1.10). Similar results were obtained for the polymerization of styrene at 110°C. The effects of polymerization temperature and solubility were studied in order to moderate the high activity of the catalyst and the poor solubility of the Cu(II) complex in monomers. Additionally, other parameters influencing this ATRP process are discussed.

No abstract

Summary: Ligands suitable for atom transfer radical polymerization (ATRP) were prepared by the Michael addition of several acrylates (allyl, benzyl, butyl, 2‐ethylhexyl, and 3‐(dimethoxymethylsilyl)propyl acrylates) with tris(2‐aminoethyl)amine (TREN). These ligands, readily prepared from inexpensive precursors, were used for the preparation of catalyst complexes suitable for polymerization of (meth)acrylates and styrene, providing activity comparable to catalysts currently used for these monomers. Catalysts containing ligands with a dimethoxymethylsilyl substituent were examined for copper removal after the reaction mixture was contacted with silica gel.magnified image

No abstract

A new simple method has been developed for the estimation of deactivation rate constants in atom transfer radical polymerization using copper catalysts. This method is based on the principle of reverse ATRP and is conducted under an air atmosphere, using molecular oxygen as an oxidant for Cu(I) species. The deactivation rate constants for several different reactive copper complexes were estimated by this procedure, and the results are correlated with those obtained from the analysis of the evolution of molecular weight distribution with conversion and with competitive trapping reactions using nitroxides. The effect of temperature on these rate constants was also studied.

No abstract

The combination of the neodymium tert-butoxide [Nd 3 (m 3 -OBu t ) 2 (m-OBu t ) 3 (OBu t ) 4 (THF) 2 ] 1 with 1 equivalent of a dialkylmagnesium reagent affords an efficient catalyst for the pseudo-living polymerization of ethylene.

Attempts to identify the intermediates and/or active species generated from binary combinations of a lanthanide alk(aryl)oxide with a dialkylmagnesium reagent, which behave as efficient olefin polymerization systems, are reported. The well‐defined trinuclear complex [Nd3(μ3‐OtBu)2(μ2‐OtBu)3(μ‐OtBu)4(THF)2] (1) and the monomeric precursor [Nd(OC6H2tBu2‐2,6‐Me‐4)3(THF)] (2) were used in association with [Mg(CH2SiMe3)2(Et2O)] (3). The new heterodimetallic complex [(THF)Nd(μ3‐OtBu)2(μ2‐OtBu)2(OtBu)Mg2(CH2TMS)2] (4) and the alkyllanthanide complex [Nd(OC6H2tBu2‐2,6‐Me‐4)2(CH2SiMe3)(THF)2] (5) have been isolated and characterized in the solid state and in solution. Complex 4 is proposed to be a reaction intermediate in the active species formation, while complex 5 is the first alkyllanthanide species isolated from an “Ln(OR)3”/MgR2 mixture, consistent with the observed behavior of these combinations in olefin polymerization. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)