Among the living radical polymerization techniques, reversible addition-fragmentation chain transfer (RAFT) and macromolecular design via the interchange of xanthates (MADIX) polymerizations appear to be the most versatile processes in terms of the reaction conditions, the variety of monomers for which polymerization can be controlled, tolerance to functionalities, and the range of polymeric architectures that can be produced. This review highlights the progress made in RAFT/MADIX polymerization since the first report in 1998. It addresses, in turn, the mechanism and kinetics of the process, examines the various components of the system, including the synthesis paths of the thiocarbonyl-thio compounds used as chain-transfer agents, and the conditions of polymerization, and gives an account of the wide range of monomers that have been successfully polymerized to date, as well as the various polymeric architectures that have been produced. In the last section, this review describes the future challenges that the process will face and shows its opening to a wider scientific community as a synthetic tool for the production of functional macromolecules and materials.

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We report the syntheses and uses of versatile chain transfer agents (CTAs) that produce well-controlled macromolecular architectures with specific chain-end functionalities, via reversible addition fragmentation chain transfer (RAFT) polymerization). Examples of architectures are given, including amphiphilic copolymers and block copolymers incorporating a biodegradable block. These CTAs are also used for the grafting of poly(styrene), poly(methyl methacrylate) and poly(methyl acrylate) from cotton.

All solvents, monomers, and other chemicals were purchased from Aldrich at the highest purity available unless otherwise stated. Methyl acrylate was filtered before utilization through a basic alumina (Brockmann I) column, to eliminate the radical inhibitor.Tetrahydrofuran (THF, Riedel-deHaën, HPLC grade) was dried over molecular sieves 4 Å. 2,2-Azobisisobutyronitrile (AIBN, 99%, Fisher) was recrystallized twice from ethanol. Sodium methanethiolate (25 wt. % in methanol), Merrifield resin and silica particles were used as received. Diethyl ether, ethyl acetate and n-hexane were purchased from Riedel-deHaën (AR grade). Methyl-α-bromophenylacetate (97%) was supplied from both Aldrich and Lancaster Synthesis. Air and moisture sensitive compounds were manipulated using standard Schlenk techniques under a nitrogen atmosphere. Characterization Techniques: -Size Exclusion Chromatography (SEC)Molecular weight distributions were recorded using size exclusion chromatography (SEC) at ambient temperature using a system equipped with a Polymer Laboratories 5.0 µm-bead-size guard column (50 × 7.5 mm) and two Polymer Laboratories PLgel 5µm MIXED-C columns (Molecular weight range of 2 000 000 -500 g mol-1) with a differential refractive index detector (Shodex, RI-101). Unless otherwise stated, tetrahydrofuran was used as an eluent at a flow rate of 1 mL min-1 and toluene was used

Magnesium and zinc complexes of the monoanionic ligands N,N'-bis(2,6-di-isopropylphenyl)triazenide, L1, N,N'-bis(2,6-di-isopropylphenyl)acetamidinate, L2, and N,N'-bis(2,6-di-isopropylphenyl)tert-butylamidinate, L3, have been synthesized, but only L3 possesses sufficient steric bulk to prevent bis-chelation. Hence, the reaction of L1H with excess ZnEt2 leads to the isolation of (L1)2Zn, 1; L1H also reacts with Bu2Mg in Et2O to afford (L1)2Mg(Et2O), 2. Similar reactivity is observed for L2H, leading to the formation of (L2)2Zn, 3, and (L2)2Mg, 4. The reaction of L2H with ZnR2 may also afford the tetranuclear aggregates {(L2)Zn2R2}2O, 5 (R=Me) and 6 (R=Et). By contrast, the tert-butylamidinate ligand was found to exclusively promote mono-chelation, allowing (L3)ZnCl(THF), 7, [(L3)Zn(micro-Cl)]2, 8, (L3)ZnN(SiMe3)2, 9, (L3)MgiPr(Et2O), 10, and (L3)MgiPr(THF), 11, to be isolated. X-ray crystallographic analyses of 1, 2, 3, 4, 5, 6, 8, and 10 indicate that the capacity of L3 to resist bis-chelation is due to greater occupation of the metal coordination sphere by the N-aryl substituents.