Methyl methacrylate nitroxide-mediated

During the last 5 years, there have been several reports of multiblock copolymer brushes by the grafting-from method. The most common substrates are gold and silicon oxide layers but there have been reports of diblock brush formation on clay surfaces [37] and silicon-hydride surfaces [38]. Most of the newer reports have utilized ATRP [34,38-43] but there have been a couple of reports that utilized anionic polymerization [44, 45]. Zhao and co-workers [21,22] have used a combination of ATRP and nitroxide-mediated polymerization to prepare mixed poly(methyl methacrylate) (PMMA)Zpolystyrene (PS) brushes from a difunctional initiator. These Y-shaped brushes could be considered block copolymers that are surface immobilized at the block junction. 

Fig. 16 Overall conversion versus (a) time and (b) number-average molar mass, M , and poly-dispersity index, A/w/Afn (the line represents the theoretical M ) for the nitroxide-mediated surfactant-free emulsion copolymerizations of methyl methacrylate and styrene in the presence of poly(PEGMA-ct>-MAA-co-styrene)-SGl macroalkoxyamines of different molar masses triangles 9400, and squares 44(X)gmol ) [145]...

Fukuyama T, Kajihara Y, Ryu I et al (2012) Nitroxide-mediated polymerization of styrene, butyl acrylate, or methyl methacrylate by microflow reactor technology. Synthesis 44 2555-2559... 

Obviously, the use of nitroxides as agents to control polymerizations remains interesting, however, their limitations makes one wonder whether there are other stable radicals which may be superior. Unfortunately, there are a limited number of stable radicals available, and those that have been studied have not been particularly successful. Earlier studies with galvi-noxyl radicals have been followed recently with the use of triazolinyl radicals and verdazyl radicals 1. However, in the only reported use of verdazyl radicals to mediate styrene polymerizations no control was observed with 2, an adduct of the 1,3,5-triphenylverdazyl radical and the 2-(2-cyano-2-propyl) radical derived from 2,2 -azobisisobutyronitrile (AIBN), at reaction temperatures between 80 °C and 120 In the case of the triazolinyl radicals, a spirotriazolinyl radical controlled the polymerization of styrene reasonably weU, but was only moderately effective for methyl methacrylate ... 

Theoretical expression of the average activation-deactivation equilibrium constant in controHed/living free-radical copolymerization operating via reversible termination. Application to a strongly improved control in nitroxide-mediated polymerization of methyl methacrylate, Macromolecules 2005, 38, 5485-5492. 

B. Charleux, S. R. A. Marque, D. Bertin, S. Magnet, L Couvreur, Living character of polymer chains prepared via nitroxide-mediated controlled free-radical polymerization of methyl methacrylate in the presence of a small amount of styrene at low temperature, Macromolecules 2006,... 

Figure 11.8 Random copolymerization of styrene with either (1) methyl methacrylate or (2) butyl acrylate by nitroxide-mediated living free-radical procedures. (Drawn following the synthesis method of ffawker et...

In a more recent study, Charleux et studied the theoretical features of the activation-deactivation equilibrium in nitroxide-mediated copolymerization and applied it to the SGl-mediated copolymerization of methyl methacrylate with a low percentage of styrene (typically in the 4-9 mol.% range). They actually demonstrated that the system exhibited all the characteristics of a living/controlled polymerization, which was explained by the following features (1) the overall concentration of propagating radicals was strongly reduced by the copolymerization effect and the irreversible termination reactions undergone by the MMA/SGf system were hence slowed down (2) isolated styrene subunits were incorporated into the chains and the terminal one promoted the reversible deactivation by the SGI nitroxide and (3) the MMA penultimate unit effect enhanced deactivation of the so-formed styryl-SGf... 

McHale R, Aldabbagh F, Zetterlund PB (2007) The role of excess nitroxide in the SGI (A-tert-butyl-A-[l-diethylphosphono-(2,2-dimethylpropyl)] nitroxide)-mediated polymerization of methyl methacrylate. J Polym Sci Part A Polym Chem 45 2194-2203... 

Qiao XG, Fansalot M, Bourgeat-Lami E, Charleux B (2013) Nitroxide-mediated polymerization-induced self-assembly of poly(poly(ethylene oxide) methyl ether methacrylate-co-styrene)-h-poly(n-butyl methacrylate-co-styrene) amphiphilic block copolymers. Macromolecules 46 4285 295... 

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