Reversible addition-fragmentation chain transfer emulsion polymerization

Reversible addition-fragmentation chain transfer (RAFT) polymerization has been one of the most promising recent advances in the controlled free radical poljmerization (CRP) technique for both the homogeneous and heterogeneous sys-tem.P The mechanism of the RAFT has been established by a dynamic equihbrium between the active and the dormant spedes.f Although RAFT polymerizations were well developed in the heterogeneous media via emulsion,minie-mulsion and ab initio emulsion polymerization, RAFT emulsion polymer-... 

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. 

The kinetics of the free radical emulsion polymerization of a-meth-ylene-y-valerolactone has been investigated (58). Stable polymer latices could be prepared. A homogeneous nucleation is the dominant path for particle formation. Also, the miniemulsion copolymerization with styrene as comonomer has been investigated. Both the reversible addition-fragmentation chain transfer (RAFT) miniemulsion polymerization and the RAFT bulk polymerization are weU controlled and copolymers with a narrow polydispersity are formed. 

Control of radical poljmerization with the addition of thiocarbonylthio compounds that serve as reversible addition fragmentation chain transfer (RAFT) agents was first reported in 1998. Since that time much research carried out in these laboratories and elsewhere has demonstrated that RAFT polymerization is an extremely versatile process.f It can be applied to form narrow polydispersity poljmers or copolymers from most monomers amenable to radical poljmerization. It is possible to take RAFT poljmerizations to high conversion and achieve commercially acceptable polymerization rates. Polymerizations can be successfully carried out in heterogeneous media (emulsion, miniemulsion, suspen-... 

B. Apostolovic, F. Quattrini, A. Butte, G. Storti, M. Morbidelh, Ah initio emulsion polymerization by RAFT (reversible addition-fragmentation chain transfer) through the addition of cyclodextrins, Helv. Chim. Acta 2006, 89, 1641-1660. 

Monteiro, M. J., and de Barbeyrac, J. (2001). Free-radical polymerization of styrene in emulsion using a reversible addition-fragmentation chain transfer agent with a low transfer constant effect on rate, particle size, and molecular weight. Macromolecules, 54(13) 4416-4423. 

Kanagasabapathy, S., Sudalai, A., and Benicewicz, B. C. (2001). Reversible addition-fragmentation chain-transfer polymerization for the synthesis of poly(4-acetoxystyrene) and poly(4-acetoxystyrene)-block-polystyrene by bulk, solution and emulsion techniques. Macromol. Rapid. Commun., 22(13) 1076-1080. 

Abstract This chapter summarizes the properties and most representative applications of pH-responsive polymers in the biomedical field.The most common methodologies to synthesize pH-responsive polymers such as emulsion polymerization, group transfer polymerization, atom transfer radical polymerization and reversible addition-fragmentation chain transfer polymerization are described. This chapter also discusses the most important applications of pH-responsive polymers in drug and gene delivery and the use of these systems as biosensors, taking into account the chemical and physical properties of these smart polymer systems. 

Hodgson, M. (2000) Emulsion Polymerization of Styrene in the Presence of Reversible Addition-Fragmentation Chain Transfer Agents. Thesis, University of Stellenbosh, South Africa. 

Since chemically grafted SPB show greater stabifity and controllable grafting density, this method of preparation has become more popular than physical adsorption. Chemical methods include photoemulsion polymerization, thermocontrolled emulsion polymerization, atom transfer radical polymerization (ATRP), and reversible addition-fragmentation chain transfer (PJVFT). 

Mballa Mballa MA, Ali SI, Heuts JPA, van Herk AM (2012) Control of the anisoUopic morphology of latex nanocomposites containing single montmorillonite clay particles prepared by conventional and reversible addition-fragmentation chain transfer based emulsion polymerization. Polym hit 61 861-865... 

Nguyen D, Such CH, Hawkett BS (2013) Polymer coating of carboxylic acid functionalized multiwalled carbon nanotubes via reversible addition-fragmentation chain transfer mediated emulsion polymerization. J Polym Sci Part A Polym Chem 51 250-257... 

Many of the papers described emulsion or miniemulsion polymerization in the presence of unmodified or modified clays (often MMT). The modifieation can be surface modification, edge modification or both. lanchis et al. claimed that they obtained both clay platelets (silylated MMT) inside the latex partieles and on the surface of latex particles. Although the elay was not easily visible in the TEM pictures presented, they indirectly inferred the presence of MMT platelets inside the latex particles by looking at the shape of the latex particles. Snowman morphologies were associated with the encapsulated clay. Recently, reversible addition-fragmentation chain transfer (RAFT)-mediated... 

The controlled emulsion polymerization of styrene using nitroxide-mediated polymerization (NMP), reversible addition-fragmentation transfer polymerization (RAFT), stable free radical polymerization (SFR), and atom transfer radical polymerization (ATRP) methods is described. The chain transfer agent associated with each process was phenyl-t-butylnitrone, nitric oxide, dibenzyl trithiocarbonate, 1,1-diphenylethylene, and ethyl 2-bromo-isobutyrate, respectively. Polydispersities between 1.17 and 1.80 were observed. 

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