Trithiocarbonate RAFT agents chain transfer polymerization

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. 

RAFT polymerizations of W-isopropylacrylamide (NIPAM) as monomer and a trithiocarbonate as chain transfer agent have been carried out using a flow microreactor under homogeneous conditions (Fig. 26) [210]. In a flow process, an increase in the inner diameter of the tube results in slightly lower conversions and wider molecular weight distributions. Polymerization rates in a flow microreactor are considerably higher than those of batch polymerization because of uniform heating (Table 6). 

RAFT polymerization produces polymers with readily modifiable co-ends. The dithioester or trithiocarbonate required for successful chain transfer can be reduced with an agent... 

MAY 00] Mayadunne R.T.A., Rizzardo E., ChiefARI J. et al, Living polymers by the use of trithiocarbonates as reversible addition-fragmentation chain transfer (RAFT) Agents ABA triblock copolymers by radical polymerization in two sissps . Macromolecules, vol. 33, pp. 243-245, 2000. 

A RAFT polymerization system consists of an initiator, monomer, solvent and a chain transfer agent, defined as RAFT agent, which mediates the polymerization via a reversible chain transfer process. RAFT agents are thiocarbonylthio compounds, including dithioesters, dithiocarbamates, trithiocarbonates and xanthates, and characterized by the presence of two different functionalities a Z group, which affects the stability of the C=S bond and controls the effectiveness radicals addition to the growing chain, and a R group, able to initiate new polymeric chains (Fig. 1.10). 

Rieger J, Osterwinter G, Bui C, Stoffelbach F, Charleux B (2009) Surfactant-free controlled/living radical emulsion (co)polymerization of n-butyl acrylate and methyl methacrylate via RAFT using amphiphilic poly(ethylene oxide)-based trithiocarbonate chain transfer agents. Macromolecules 42 5518-5525... 

Rieger J, Zhang W, Stoffelbach F, Charleux B (2010) Surfactant-free RAFT emulsion polymerization using poly(N, N-dimethylacrylamide trithiocarbonate macromolecular chain transfer agents. Macromolecules 43 6302-6310... 

The trithiocarbonates, such as RT-11 and RT-12 in Scheme 3.8 are another type of difunctional transfer agent, and can be used in the RAFT polymerization of monomer A. One way to confirm the presence of an active trithiocar-bonate group located in the center is to cleave the polymer chains at the trithiocarbonate function. This can be achieved in the presence of mild nucleophiles such as primary or secondary amines. Generally, the molecular weight of... 

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