This Perspective describes the recent developments of polymerization-induced self-assembly of amphiphilic block copolymers based on controlled/living free-radical polymerization (CRP) in water. This method relies on the use of a hydrophilic living polymer precursor prepared via CRP that is extended with a hydrophobic second block in an aqueous environment. The process thus leads to amphiphilic block copolymers that self-assemble in situ into self-stabilized nano-objects in the frame of an emulsion or dispersion polymerization process. Depending on the nature and the structure of the so-formed copolymer, not only spherical particles can be achieved but also all morphologies that can be found in the phase diagram of an amphiphilic block copolymer in a selective solvent. This paper focuses mainly on aqueous emulsion or dispersion polymerization and gives an overview of the CRP techniques used, the general conditions, and the morphologies obtained.

After a brief history that positions polymerization‐induced self‐assembly (PISA) in the field of polymer chemistry, this Review will cover the fundamentals of the PISA mechanism. Furthermore, this Review will also give an overview of some of the features and limitations of RAFT‐mediated PISA in terms of the choice of the components involved, the nature of the nanoobjects that can be obtained and how the syntheses can be controlled, as well as some potential applications.

A hydrophilic poly(methacrylic acid-co-poly-(ethylene oxide) methyl ether methacrylate) copolymer with a trithiocarbonate reactive group was used in the free-radical, batch emulsion polymerization of styrene. It allowed fast polymerizations and high final conversions to be achieved, and the parameters for a good control over the formation of well-defined amphiphilic diblock copolymers were identified. These diblock copolymers self-assembled in situ into nanoobjects of various morphologies upon chain extension. Achieving a good control over the formed diblock copolymers was shown to be an important step toward a better understanding of the parameters that affect the shape and size of the self-assembled objects, the ultimate goal being the ability to predict and fine-tune them on purpose.

In simulations and experiments, we study the drying of films containing mixtures of large and small colloidal particles in water. During drying, the mixture stratifies into a layer of the larger particles at the bottom with a layer of the smaller particles on top. We developed a model to show that a gradient in osmotic pressure, which develops dynamically during drying, is responsible for the segregation mechanism behind stratification.

The emulsion polymerization of styrene in the presence of hydrophilic poly(methacrylic acid-co-poly(ethylene oxide) methyl ether methacrylate), P(MAA-co-PEOMA), macromolecular RAFT (reversible addition−fragmentation chain transfer) agents possessing a trithiocarbonate reactive group and 19 ethylene oxide subunits in the grafts was performed to create in situ P(MAA-co-PEOMA)-b-polystyrene amphiphilic block copolymer self-assemblies. The system was studied using the following conditions: a pH of 5, two different compositions of the MAA/PEOMA units (50/50 and 67/33, mol/mol), different molar masses of the macroRAFT agents, and various concentrations of the latter targeting different molar masses for the polystyrene block. This work completes a previous one performed at pH 3.5, under otherwise similar experimental conditions, for which only spherical particles were obtained [Zhang et al. Macromolecules 2011, 44, 7584]. For both MAA/PEOMA compositions, the system led to different nano-object morphologies such as spherical micelles, nanofibers, and vesicles, depending directly on the molar masses of the hydrophilic and hydrophobic blocks. A pH of 5 was shown to be the best compromise to achieve nonspherical particles while keeping a good control over the chain growth.

The RAFT-mediated emulsion polymerization of styrene was carried out in a one-pot, two-step procedure using two poly-(methacrylic acid-co-poly(ethylene oxide) methyl ether methacrylate) macroRAFT agents of different compositions carrying a reactive trithiocarbonate end-group. The latter were prepared in situ, directly in aqueous solution at acid pH. In all cases, the synthesis was fast and efficient, leading to very high conversions and very good control over the polymer features. It was moreover particularly reproducible, which is an important outcome for the robustness of the method. Then, styrene was added and directly polymerized in the formed emulsion system until very high conversion in short reaction time. The method led to amphiphilic block copolymers, self-assembled into stable spherical particles. The diameter of the latter was directly governed by the initial concentration of macroRAFT agent, which also controlled the molar mass of the polystyrene block at constant styrene initial concentration. The emulsion polymerization step was studied in detail to provide information on the overall mechanism: nucleation, conversion rate, and chain growth. Because of the reduction of the number of synthesis and purification steps and of the overall reaction time, and due to the use of water as the sole reaction medium, the proposed method is of high interest in terms of both respect of environmental constraints and energy saving. ' INTRODUCTIONThe development of controlled/living free radical polymerization (CRP) 1À5 in aqueous emulsion systems has attracted much interest in the past 10 years due to the multiple advantages of the process (among others, it is environmentally friendly and favors high rates along with low viscosity) and the large number of industrial applications of the products. 6 Moreover, new possibilities are offered by the combination of both approaches. 7À14 For instance, the generation of amphiphilic block copolymers in situ, by taking advantage of the reactivity of water-soluble polymers tailored by CRP, leads to a new way of performing surfactant-free emulsion polymerization. The method leads to self-stabilized particles and can allow high solids content to be achieved, even under batch conditions. This strategy has been employed using the various CRP techniques available (mainly nitroxide-mediated radical polymerization, 15À20 organotellurium-mediated radical polymerization, 21,22 and RAFT for reversible additionÀfragmentation chain transfer 23À36 ). Most

The present paper describes the successful onepot synthesis of self-stabilized particles composed of amphiphilic block copolymers based on poly(methacrylic acid) (PMAA) obtained by polymerization-induced selfassembly. First, controlled radical polymerization of MAA is performed in water using the RAFT process by taking advantage of our recent results showing the successful RAFT polymerization of MAA in water [Chaduc et al. Macromolecules 2012, 45, 1241−1247. The so-formed hydrophilic macro-RAFT agents are then chain-extended in situ with a hydrophobic monomer to form amphiphilic block copolymer chains of controlled molar mass that self-assemble into stable nanoparticles. Various parameters such as the pH, the molar mass and the concentration of the PMAA segments or the nature of the hydrophobic block have been investigated.

International audienceThe reversible addition-fragmentation chain transfer (RAFT) polymerization of acrylic acid (AA) in water was studied in detail at different pHs using 4-cyano-4-thiothiopropylsulfanyl pentanoic add (CTPPA) as a control agent and 4,4'-azobis(4-cyanopentanoic acid) (ACPA) as an initiator. Well-defined hydrophilic macromolecular RAFT agents (PAA-CTPPA) were obtained and further used directly in water for the polymerization of styrene. The corresponding polymerization-induced self-assembly (PISA) process was evaluated at different pHs and it was shown that working in acidic conditions (pH = 2.5) led to well-defined amphiphilic block copolymer particles (D < 1.4) of small size (below 50 nm). When the pH increased, the control over the growth of the polystyrene (PS) block was gradually lost. Chain extension experiments of PAA-CTPPA with N-acryloylmorpholine (NAM), a hydrosoluble and non-pH sensitive monomer, performed at different pHs showed that the very first addition-fragmentation steps that occurred in water were impeded when PAA was ionized leading to partial consumption of PAA-CTPPA and thus to PS molar masses higher than expected. Varying the PAA-CTPPA concentration at pH = 2.5 led in all cases to stable particles composed of well-defined block copolymers with PS segments of different molar masses