Introduction 1104 2. Common Radical Synthesis of Alkoxyamines Active in NMP 1106 3. Nitrones: Precursors of Nitroxides for the Synthesis of Alkoxyamines and in-Situ NMP 1107 3.1. Nitrones as Precursors of Nitroxides 1107 3.2. Contributions of Nitrones to the in-Situ NMP 1107 3.3. Cyclic Oxazolidine as Initiator and Regulator for the Radical Polymerization of Vinyl Monomers 1111 3.4. Advantages and Drawbacks of the Nitrone Systems 1112 4. Nitroso Compounds 1112 4.1. Reaction of C-Nitroso Compounds with Free Radicals 1112 4.2. Use of C-Nitroso Compounds in Controlled Radical Polymerization 1113 4.3. Limitations of C-Nitroso Compounds 1116 5. Sodium Nitrite and NO/NO 2 Mixtures for the in-Situ NMP 1116 5.1. Preliminary Results and Mechanistic Considerations 1116 5.2. Controlled Radical Polymerization of Alkyl Methacrylates in the Presence of the in-Situ-Formed R-Nitro-ω-nitroso Adducts 1117 5.3. NO/NO 2 Mixtures: An Alternative Way to the Nitroso Compounds as Precursors of Nitroxides 1118 5.4. Advantages and Limitations of the Sodium Nitrite and NO/NO 2 Systems 1118 6. Hindered Secondary Amines and the in-Situ NMP 1118 6.1. Oxidation of Secondary Amines into Nitroxides 1118 6.2. One-Pot Processes for the Preparation of Alkoxyamines Active in NMP 1118 6.3. In-Situ NMP Using Hindered Secondary Amines and Oligomeric Secondary Amines 1120 6.4. Advantages and Limitations 1120 7. Hydroxylamines and the in-Situ NMP 1120 7.1. Oxidation of Hydroxylamines into Nitroxides 1120 7.2. Hydroxylamines and the in-Situ NMP 1120 7.3. High Molecular Weight Hydroxylamines for the Polymerization of Vinyl Monomers and Synthesis of Block Copolymers 1122 7.4. Advantages and Limitations 1122 8. Conclusions 1122 9. Acknowledgments 1123 10. References 1123

Novel copolymer brushes have been synthesized by a two-step "grafting from" method that consists of the electrografting of poly(2-phenyl-2-(2,2,6,6-tetramethyl-piperidin-1-yloxy)-ethylacrylate) onto stainless steel, followed by the nitroxide-mediated radical polymerization of 2-(dimethylamino ethyl)acrylate and styrene or n-butyl acrylate, initiated from the electrografted polyacrylate chains. The grafted copolymers were quaternized in order to endow them with antibacterial properties. Peeling tests have confirmed the strong adhesion of the grafted copolymer onto the stainless steel substrate. Quartz crystal microbalance experiments have proven that fibrinogen adhesion is lower on the hydrophilic quaternized films compared to the nonionic counterpart. Such quaternized copolymers exhibit significant antibacterial activity against the Gram-positive bacteria S. aureus and the Gram-negative bacteria E. coli.

International audienceHere we report on an all-in-one approach to prepare robust antimicrobial films on stainless steel. The strategy is based on the layer-by-layer deposition of polyelectrolytes. A polycationic copolymer bearing 3,4-dihydroxyphenylalanine units (DOPA, a major component of natural adhesives) was synthesized and co-deposited with precursors of silver nanoparticles as the first layer. The presence of DOPA units ensures a strong anchoring on the stainless steel substrate, and the silver nanoparticles are sources of biocidal Ag+, providing stainless steel with antimicrobial activity. We show that multilayered films, obtained by alternating this nanoparticle-loaded polycationic copolymer with polystyrene sulfonate, a commercial polyanion, results in stainless steel with high antibacterial activity against Gram-negative E. coli bacteria. The polycationic layers are a reservoir of Ag+ that can be reactivated after depletion. The whole process of film formation, including the synthesis of the copolymer, is conducted in aqueous media under very mild conditions, which makes it very attractive for industrial scale-up and sustainable applications

Multi-walled carbon nanotubes (MWNTs) have been successfully modified by polystyrene, poly( -caprolactone), and their block copolymers by addition reaction of the alkoxyamine-terminated precursors. Polymer-modified MWNTs are easily dispersed in good solvents for the grafted polymer, such as toluene and THF. This observation has been confirmed by TEM analysis. The grafting ratio of polystyrene chains at the surface of MWNTs depends on the polymer molecular weight.

Radical polymerization of styrene and copolymerization of styrene and acrylonitrile (60/ 40) are controlled when conducted in the presence of N-tert-butyl-R-isopropylnitrone, which is easily synthesized from cheap reagents. However, for the control to be effective, the nitrone has to be prereacted with the radical initiator. Nitroxides are then formed "in situ", such that this nitrone system is an attractive alternative for the classical nitroxide-mediated polymerization (NMP), which may require a multistep synthesis of nitroxides or alkoxyamines. The choice of the radical initiator is important because it dictates the structure of the nitroxide and thus its capacity to control the radical polymerization. Well-defined poly(styrene)-b-poly(styrene-co-acrylonitrile), poly(styrene)-b-poly(n-butyl acrylate), and poly(styrene)-bpoly(isoprene) copolymers have been successfully synthesized by this process.

Kinetics of the free radical polymerization of styrene at 110 °C has been investigated in the presence of C‐phenyl‐N‐tert‐butylnitrone (PBN) and 2,2′‐azobis(isobutyronitrile) (AIBN) after prereaction in toluene at 85 °C. The effect of the prereaction time and the PBN/AIBN molar ratio on the in situ formation of nitroxides and alkoxyamines (at 85 °C), and ultimately on the control of the styrene polymerization at 110 °C, has been investigated. As a rule, the styrene radical polymerization is controlled, and the mechanism is one of the classical nitroxide‐mediated polymerization. Only one type of nitroxide (low‐molecular‐mass nitroxide) is formed whatever the prereaction conditions at 85 °C, and the equilibrium constant (K) between active and dormant species is 8.7 × 10−10 mol L−1 at 110 °C. At this temperature, the dissociation rate constant (kd) is 3.7 × 10−3 s−1, the recombination rate constant (kc) is 4.3 × 106 L mol−1 s−1, whereas the activation energy (Ea,diss.), for the dissociation of the alkoxyamine at the chain‐end is ∼125 kJ mol−1. Importantly, the propagation rate at 110 °C, which does not change significantly with the prereaction time and the PBN/AIBN molar ratio at 85 °C, is higher than that for the thermal polymerization at 110 °C. This propagation rate directly depends on the equilibrium constant K and on the alkoxyamine and nitroxide concentrations, as well. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1219–1235, 2007

The ability of several nitrones to control the radical polymerization of styrene at 110 °C has been investigated by high-throughput experimentation. The nitrone/free radical initiator pair dictates the structure of the nitroxide and the alkoxyamine formed in situ, which determines the position of the equilibrium between the active and the dormant species operating in the nitroxide-mediated polymerization. For the styrene polymerization to be controlled, the nitrone must be reacted with 2,2′-azo-bis-isobutyronitrile (AIBN) at 85 °C, prior to addition of styrene and polymerization at 110 °C. The effect of the nitrone structure on the kinetics of the styrene polymerization has been emphasized. Amongst all the nitrones tested, those of the C-phenyl-N-tert-butylnitrone (PBN) type are the most efficient in terms of polymerization rate, control of molecular weight and polydispersity. Electrophilic substitution of the phenyl group of PBN by either an electrodonor or an electroacceptor group has only a minor effect on the polymerization kinetics. Importantly, the polymerization rate is not governed by the thermal polymerization of styrene but by the alkoxyamine formed in situ during the pre-reaction step. The initiation efficiency is, however, very low, consistent with a limited conversion of the nitrone into nitroxide and alkoxyamine.

Cobalt complexes supported on silica and Merrifield resin are effective mediators for the controlled radical polymerization of vinyl acetate.