Reversible addition-fragmentation chain transfer miniemulsion polymerization

Living radical polymerizations in miniemulsions have also been conducted by de Brouwer et al. using reversible addition-fragmentation chain transfer (RAFT) and nonionic surfactants [98]. The polydispersity index was usually below 1.2. The living character is further exemplified by its transformation into block copolymers. 

Using NMP [114, 115] or reversible addition-fragmentation chain transfer (RAFT) [ 119,120,127], agents with ammonium groups for the ion exchange allowed the attachment of initiators on the clay surface for controlled radical polymerizations (NMP, RAFT). Samakande et al. investigated the kinetics of RAFT-mediated living polymerization of styrene [120] and styrene/BA [119] mixtures in miniemulsion. 

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. 

Russum JP, Jones CW, SchorkFJ (2004) Continuous reversible addition-fragmentation chain transfer polymerization in miniemulsion utilizing a multi-tube reaction system. Macromol Rapid Commun 25 1064—1068... 

Russum JP, Jones CW, Schork FJ (2005) Continuous living polymerization in miniemulsion using reversible addition fragmentation chain transfer (RAFT) in a mbular reactor. Ind Eng Chem Res 44 2484-2493... 

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-... 

No.25, 12th Dec.2000, p.9239-46 LIVING RADICAL POLYMERIZATION IN MINIEMULSION USING REVERSIBLE ADDITION-FRAGMENTATION CHAIN TRANSFER... 

Living free radical polymerizations were also carried out in miniemulsion systems via the reversible addition-fragmentation chain transfer mechanism [66]. The colloidal stability of miniemulsions is the key issue, and nonionic surfactants result in the best results. The polydispersity index of molecular weight distribution for the resultant miniemulsion polymer is generally smaller than 1.2. 

Esteves ACC, Hodge P, Trindade T, Barros-Timmons AMMV (2009) Preparation of nanocomposites by reversible addition-fragmentation chain transfer polymerization from the surface of quantum dots in miniemulsion. J Polym Sci Part A Polym Chem 47 5367-5377... 

The use of a reversible addition-fragmentation chain transfer (RAFT)-con-trolled polymerization method to synthesize polystyrene-clay nanocomposites in miniemulsion was reported by Samakande et For this purpose, the RAFT-grafted montmorillonite clays A,A-dimethyl-A-(4- [(phenylcarbonothioyl)thio]-methyl benzyl)ethanammonium-MMT (PCDBAB-MMT) and A-[4-( [(dodecyl-thio)carbonothioyl]thio methyl)benzyl]-A,A-dimethylethanammonium-MMT (DCTBAB-MMT), were used in different amounts. 

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... 

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