Atom transfer radical polymerization.

Metal-catalyzed living radical polymerization.

Controlled/living radical polymerization: Features, developments, and perspectives

Keywords: Fragmentation Chain-Transfer ; Self-Assembled Monolayers ; Walled Carbon Nanotubes ; Well-Defined Polymer ; Nitroxide-Mediated Polymerization ; Block-Copolymer Brushes ; Poly(Methyl Methacrylate) Brushes ; Transfer Raft Polymerization ; Quartz-Crystal Microbalance ; Poly(Acrylic Acid) Brushes Reference EPFL-REVIEW-148464doi:10.1021/cr900045aView record in Web of Science Record created on 2010-04-23, modified on 2017-05-10

Polymer Brushes via Surface-Initiated Controlled Radical Polymerization: Synthesis, Characterization, Properties, and Applications

Functional polymers by atom transfer radical polymerization

Halide exchange during atom transfer radical polymerization (ATRP) using mixed halide initiation systems, R−X/Cu−Y (X, Y = Cl or Br), was investigated. Model studies of mixed halide initiation systems (i.e., R−X/Cu−Y, X ≠ Y) demonstrated that exchange occurs rapidly at 90 °C, and there is a clear preference for alkyl chlorides to be formed in over alkyl bromides. This was attributed mainly to the carbon−chlorine bond being stronger than the corresponding carbon−bromine bond. This implies that, in ATRP with a mixed halide initiator/catalyst system, the bulk of the polymer chain ends are terminated by chlorine if [CuCl]0 ≥ [RBr]0. Examples of using this information to improve the control in ATRP of methyl methacrylate (MMA) are presented. It was shown that, when benzyl halides were used as the initiator in the ATRP of MMA, the rate of initiation was increased relative to the rate of propagation, thus providing better control by using the benzyl bromide/copper chloride mixed halide system. Better molecular w...

Utilizing Halide Exchange To Improve Control of Atom Transfer Radical Polymerization

The homogeneous controlled/“living” free radical polymerization of methyl methacrylate (MMA) by atom transfer radical polymerization (ATRP) using a CuIX/4,4‘-di(5-nonyl)-2,2‘-bipyridine catalytic system (X = Cl, Br) with various initiators R−X was investigated. The rates of polymerization initiated by most of the systems exhibited first-order kinetics with respect to the monomer. A linear increase of number average molecular weight (Mn) versus monomer conversion was observed for most of these initiation systems. The benzhydryl chloride/CuICl system yielded the lowest rate of polymerization, which could be increased by slow addition of the initiator. The reduced rate of polymerization was due to an increase in the concentration of CuIICl, which results from the coupling of benzhydryl radicals during initiation. The slow addition of benzhydryl chloride prevented the formation of a large amount of benzhydryl radicals in the initiation step, thereby reducing radical−radical termination and CuII formation, and...

Controlled/“Living” Atom Transfer Radical Polymerization of Methyl Methacrylate Using Various Initiation Systems

One of the most important goals of synthetic polymer chemistry is to gain control not only over the molecular weights and polydispersities of polymer chains, but also their architecture and end-groups. Living polymerizations, in which neither transfer nor termination takes place, appeared to be the best technique to reach this target.1 Mainly performed by anionic,2 cationic,3 or group transfer polymerization,4 living polymerizations require specific experimental conditions that often make their industrial application difficult. Recently, controlled/ “living” approaches to radical polymerizations were reported.5-11 In these processes, the contribution of termination and transfer reactions remains very low,7 although they cannot be completely eliminated. One of the most successful controlled/“living” radical polymerization methods developed is atom transfer radical polymerization9 (ATRP). It has its roots in organic chemistry’s atom transfer radical addition12,13 (ATRA), which is sometimes called Kharasch addition.14 ATRP has been proven to be effective for a wide range of monomers15 and appears to be a powerful tool for the polymer chemist, providing new possibilities in structural and architectural design16 and allowing the development of new materials with monomers currently available.17,18 This communication reports that atom transfer radical polymerization can be used successfully to control the polymerization of methyl methacrylate (MMA) over a broad range of molecular weights, reaching very low polydispersities, with easy reaction conditions and relatively rapid kinetics. As reported by Sawamoto,10,19 ATRP based on ruthenium catalytic systems allows for control of the polymerization of MMA untilMn ) 20 000 with slow reaction rates (typically 80% conversion in 20-30 h). By using a homogeneous ATRP catalytic system based on copper bromide and a substituted bipyridyne, we were able to synthesize poly(MMA) with polydispersities as low as 1.1 (Mn ) 20 000) in a few hours while controlling molecular weights until Mn ) 180 000. MMA was polymerized with p-toluenesulfonyl chloride (p-TSCl) in conjunction with copper(I) bromide (CuBr) and 4,4′-bis(5-nonyl)-2,2′-bipyridine (dNbipy)20 in diphenyl ether (DPE) at 90 °C.21 p-Toluenesulfonyl chloride was used as an initiator for styrene polymerization22,23 and in metal-catalyzed ATRA. When aiming at PMMA of Mn ) 20 000 at 100% conversion (Figures 1 and 2), /2 equiv of catalyst to initiator was used in order to reduce the amount of radicals in the medium. Complexation of copper by 4,4′-bis(5-nonyl)-2,2′-bipyridine allowed the reaction mixture to be homogeneous. As shown in Figure 1, 80% conversion was reached in 5 h, and semilogarithmic kinetic plots are linear, indicating that the radical concentration is constant during the polymerization. A linear increase of number average molecular weight, Mn,SEC, vs monomer conversions up to 95% was found (Figure 2). The Mn,SEC is very close to the theoretical one, Mn,th, defined by eq 1,24 which assumes that one molecule of initiator generates one growing polymer chain:

Controlled/“Living” Radical Polymerization of Methyl Methacrylate by Atom Transfer Radical Polymerization

The homogeneous controlled/“living” radical polymerization of methyl methacrylate (MMA) using the atom transfer radical polymerization (ATRP) with CuCl/4,4‘-di(5-nonyl)-2,2‘-bipyridine catalytic system and diphenyl ether as the solvent generated well-defined polymers with polydispersities Mw/Mn ≤ 1.2. The evolution of the molecular weights of the polymers follows the ratio of the mass of the consumed monomer to the initial initiator concentration. The rate of polymerization follows first-order kinetics with respect to the decrease of monomer concentration. The polymerization rate reaches a maximum when the ratio of ligand-to-CuICl is one-to-one. ATRP of MMA shows first-order kinetics with respect to both CuICl and the initiator, alkyl or sulfonyl chloride. The rate of polymerization did not obey simple negative first-order kinetics with respect to the concentration of CuIICl, partially due to a persistent radical effect, which resulted in the increase of [CuIICl] in the initial stage of polymerization. Th...

Thomas Grimaud

Papers

Utilizing Halide Exchange To Improve Control of Atom Transfer Radical Polymerization

Controlled/“Living” Atom Transfer Radical Polymerization of Methyl Methacrylate Using Various Initiation Systems

Controlled/“Living” Radical Polymerization of Methyl Methacrylate by Atom Transfer Radical Polymerization

Kinetic Study of the Homogeneous Atom Transfer Radical Polymerization of Methyl Methacrylate

Novel methodology for interpolation of radiation-induced attenuation in optical fibers