Addition-fragmentation chain transfer reviews

Although the term RAFT (an acronym for Reversible Addition-Fragmentation chain Transfer)38" is sometimes used in a more general sense, it was coined to describe, and is most closely associated with, the reaction when it involves thiocarbonylthio compounds. RAFT polymerization, involving the use of xanthates, is also sometimes called MADIX (Macromolccular Design by Interchange of Xambate) 96 The process has been reviewed by Rizzardo et [Pg.502]

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. 

In this review, the term macromer is used to describe oligomer or polymer precursors that undergo reversible association to form supramolecular polymers or networks. Macromer synthesis, although a crucial aspect of supramolecular science, is also out of the scope of this review. Several comprehensive reviews of the synthesis of H-bonding polymers are available [10, 11,42] and primarily describe the application of controlled radical polymerization techniques, including atom-transfer radical polymerization (ATRP), reversible addition-fragmentation chain transfer (RAFT) polymerization, and nitroxide-mediated polymerization (NMP). For synthesis of telechelic polymers, avoiding monofunctional impurities that can act as chain stoppers is crucially important [43],... 

This chapter serves as a brief overview of the controlled radical polymerization methods, atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT) polymerization, and their utilization in the construction of solution-based stimuli-responsive polymers. The structure/property/behavior relationships of selected systems are discussed relative to changes in pH, tanperature, and electrolyte concentration. Additionally, comprehensive reviews are cited for additional information. 

Addition-fragmentation chain transfer has been reviewed by Rizzardo et Colombani and Chaumont, ... 

Addition-fragmentation chain transfer agents and their application to control molecular weight and end-group functionality have been reviewed by Rizzardo and coworkers, " Colombani and Chaumont, Colombani, Yagci and Reetz, Yamada and coworkers, and Moad and Solomon. ... 

This chapter presents a review of polymer-clay nanocomposites (PCNs) prepared in miniemulsion using the reversible addition-fragmentation chain transfer (RAFT) process. 

Enzymatic ROP has also been successfully combined with chemically catalyzed polymerization methods in SCCO2, allowing the formation of block structures. For example, Howdle and coworkers reported a simultaneous use of Novozym 435 with metalblock copolymers of PCL and PMMA [107, 108], whilst a two-step methodology was used to form block copolymers of PCL with poly(fluoro-octyl methacrylates) (PFOMA) [109]. Similar reactions, simultaneously combining reversible addition-fragmentation chain transfer (RAFT) with enzymatic ROP to form block copolymers of polystyrene and PCL, have also been performed in SCCO2 [110]. Block copolymer synthesis in SCCO2 has recently been reviewed [111]. 

General aspects of chain transfer have been reviewed by Chiefari and Rizzardo,3 Barson, 1 Farina/ Fastmond6 and Palit el al1 The use of chain transfer in producing lelechelic and other functional polymers has been reviewed by Boutevin,8 Heitz/ Comer10 and Starks11 and is discussed in Section 7.5.2. There are two main mechanisms which should be considered in any discussion of chain transfer (a) atom or group transfer by homolytie substitution (Section 6.2.2) and (b) addition-fragmentation (Section 6.2.3). 

Several reviews devoted to CRP have been already been published, and readers may refer to proceedings from ACS Meetings on CRP [42,43], general reviews on CRP [44-48], reviews on ATRP [30,49-54], on macromolecular engineering and materials prepared by ATRP [55], on nitroxide mediated polymerization (NMP) [56-58], on catalytic chain transfer [59,60], and on reversible addition fragmentation transfer polymerization, RAFT [61]. 

The fragmentation of radical anions and the reverse reaction, the addition of anions to radicals, are the critical steps of SRN1 reactions [110] which constitute perhaps the largest class of fragmentation reactions initiated by photoinduced electron transfer. These reactions are chain processes and photoinduced ET is involved only in the initiation step, which is usually poorly defined. The reactions may also be initiated by other means, not involving absorption of a photon. The SRN1 reactions and related redox-activation processes have been recently extensively reviewed [72a, 110,127] and will not be discussed here. 

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