Atom transfer radical polymerization miniemulsion

FIGURE 54.23 A schematic representation of inverse miniemulsion or microemulsion polymerization for the preparation of nanometer-sized particles of water-soluble and water-swellable polymers as well as cross-linked particles in the presence of cross-linkers. (Reprinted from Polymer, 50(19), Oh, J.K., Bencherif, S.A., and Matyjaszewski, K., Atom transfer radical polymerization in inverse miniemulsion A versatile route toward preparation and functionalization of microgels/nanogels for targeted drug delivery applications, 4407-4423. Copyright 2009, with permission from Elsevier.)... 

Oh, J.K. Bencherif, S.A. Matyjaszewski, K. Atom transfer radical polymerization in inverse miniemulsion A versatile route toward preparation and funetionalization of microgels/nanogels for targeted drug delivery applications. Polymer 2009,50 (19), 4407-4423. 

Taking into account all of the above mentioned applications, the synthesis of magnetic latex will be discussed in two parts first, the preparation of iron oxide nanoparticles and, second, the preparation of magnetic latex. Depending on the aim of researchers, many polymerization techniques are applied such as suspension, dispersion, emulsion, microemulsion and miniemulsion polymerization in combination with controlled radical polymerization techniques like atom transfer radical polymerization (ATRP), reversible addition-fragmentation chain transfer (RAFT) and nitroxide-mediated radical polymerization (NMP). The preparation of hybrid magnetic latex by emulsion polymerization will be the focus of this review. 

Controlled radical polymerization techniques are suitable for synthesizing polymers with a high level of architectural control. Notably, they not only allow a copolymerization with functional monomers (as shown previously for free-radical polymerization), but also a simple functionalization of the chain end by the initiator. Miniemulsion systems were found suitable for conducting controlled radical polymerizations [58-61], including atom transfer radical polymerization (ATRP), RAFT, degenerative iodine transfer [58], and nitroxide-mediated polymerization (NMP). Recently, the details of ATRP in miniemulsion were described in several reviews [62, 63], while the kinetics of RAFT polymerization in miniemulsion was discussed by Tobita [64]. Consequently, no detailed descriptions of the process wiU be provided at this point. 

Matyjaszewski, K., et al. (2000). Atom transfer radical polymerization of n-butyl methacrylate in an aqueous dispersed system a miniemulsion approach. J. Polym. ScL, Part A Polym. Chem., 35(Suppl.) 4724 734. 

Dong H., Mantha V. and Matyjaszewski K. (2009), Thermally responsive PM(EO)2MA magnetic microgels via activators generated by electron transfer atom transfer radical polymerization in miniemulsion. Chemistry of Materials, 21 pp. 3965-3972. 

Li M, Matyjaszewski K. Reverse atom transfer radical polymerization in miniemulsion. Macromolecules 200336 6028-6035. 

Khezri K, Haddadi-Asl V, Roghani-Mamaqani H, Salami-Kalajahi M (2011) Synthesis and characterization of exfohated poly(styrene-co-methyl methacrylate) nanocomposite via miniemulsion atom transfer radical polymerization an activators generated by electron transfer approach. Polym Comp 32 1979-1987... 

Kagawa, Y., Zetterlund, P.B., Minami, H., Okubo, M. Atom transfer radical polymerization in miniemulsion partitioning effects of copper(I) and copper(II) on polymerization rate, Uv-ingness, and molecular weight distribution. Macromolecules 40(9), 3062-3069 (2007)... 

Simms, R.W., Cunningham, M.F. Reverse atom transfer radical polymerization of butyl methacrylate in a miniemulsion stabilized with a cationic surfactant. J. Polym. Sd. Part A Polym. Chem. 44(5), 1628-1634 (2006)... 

Elsen, A.M., Butdynska, J., Park, S., Matyjaszewski, K. Activators regenerated by electron transfer atom transfer radical polymerization in miniemulsion with 50 ppm of copper catalyst. ACS Macro. Lett. 2(9), 822-825 (2013)... 

Reversible atom transfer free radical polymerization of n-butyl acrylate was conducted in miniemulsion systems using the water-soluble initiator 2,2 -azobis(2-amidinopropane) dihydrochloride (V-50) and the hydrophobic ligand 4,4 -di(5-nonyl)-4,4 -bipyridine to form a complex with the copper ions [67, 80]. The resultant Cu(II) complex has a relatively large solubility in the continuous aqueous phase, but this should not impair its capability of controlling the free radical polymerization. This is because the rapid transport of the Cu(II) complex between the dispersed organic phase and the continuous aqueous phase assures an adequate concentration of the free radical deactivator. As a consequence, the controlled free radical polymerization within the homogenized monomer droplets can be achieved. 

Simultaneous normal and reverse initiation (SR NI) ATRP (Fig. 1.17c) was developed to allow the precursors of highly active catalytic complexes to be added to the reaction in the higher oxidation state and at lower concentration. SR NI ATRP comprises a dual initiation system i.e. standard free radical initiators and initiators comprising a transferable atom or group in conjunction with the stable precursor of an active catalyst complex. This initiation system can be used to prepare any type of polymer that can be obtained by normal ATRP, and can be conducted in bulk, solution, emulsion, miniemulsion, and by heterogeneous polymerization. 

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