Well-defined water-soluble brush-type homopolymers and copolymers entirely composed of poly(ethylene)oxide methacrylate (PEOMA) units with PEO side groups of various chain lengths (M n = 300 and 950 g mol–1) were synthesized by nitroxide-mediated polymerization (NMP) using a low molar mass unimolecular alkoxyamine initiator (so-called BlocBuilder) and N-tert-butyl-N-(1-diethyl phosphono-2,2-dimethyl propyl) nitroxide (SG1) in the presence of a small amount of styrene. The resulting SG1-capped macroalkoxyamines possessed the predicted molar masses based on the monomer/initiator molar ratio and narrow molar mass distributions. They were then employed to initiate the emulsion polymerization of n-butyl methacrylate with a low amount of styrene under mild conditions (85 °C) leading to amphiphilic block copolymers that in situ self-assembled into sterically stabilized particles. Kinetics study confirmed the living character of the polymerization, while SEC analysis indicated the presence of a small fraction of dead chains formed by irreversible homotermination reactions. Spherical latex particles with diameters comprised between 60 and 300 nm were obtained at pH 4.2 when decreasing the macroinitiator concentration from 7.2 to 1.2 mM in agreement with the in situ formation of block copolymers. As expected, only the macroinitiators with long PEO side groups, and whose cloud points were above the reaction temperature, led to stable latex suspensions. A drastic change in particle morphology with the formation of vesicles and anisotropic objects was observed when increasing the suspension pH from 4.2 to 6.7. As the macroalkoxyamine initiator contained only one terminal methacrylic acid unit, such a strong effect of pH on particles morphology was not expected. The observed results were interpreted in terms of a salting out effect induced by the concomitant increase of ionic strength upon neutralization of the alkoxyamine initiator. Hence, particle morphologies could be tuned from spherical to elongated micelles and vesicles by the addition of increasing amounts of sodium chloride at a fixed pH of 4.2, which confirmed the above hypothesis.

Photoinduced atom transfer radical polymerization (ATRP) has been proved to be a versatile technique for polymer network formation. However, the slow polymerization rates of typical ATRP limited its application in the field of additive manufacturing (3D printing). In this work, we introduced carbon quantum dots (CQDs) for the first time to the ATRP in aqueous media and developed an ultrafast visible-light-induced polymerization system. After optimization, the polymerization could achieve a high monomer conversion (>90%) within 1 min, and the polydispersity index (PDI) of the polymer was lower than 1.25. This system was then applied as the first example of ATRP for the 3D printing of hydrogel through digital light processing (DLP), and the printed object exhibited good dimensional accuracy. Additionally, the excellent and stable optical properties of CQDs also provided interesting photoluminescence capabilities to the printed objects. We deduce this ATRP mediated 3D printing process would provide a new platform for the preparation of functional and stimuli-responsive hydrogel materials.

We report the first nitroxide-mediated synthesis of multipod-like silica/polymer latexes by polymerizationinduced self-assembly (PISA) of amphiphilic block copolymers in aqueous emulsion. A water-soluble brush-type PEO-based macroalkoxyamine initiator composed of poly(ethylene oxide) methacrylate and a small amount of styrene (P-[(PEOMA 950 ) 12 -co-S 1 ]-SG1, M n = 11 700 g mol −1 and M w / M n = 1.11) was synthesized and physically adsorbed on the surface of silica particles through hydrogen-bonding interactions. The adsorbed macroalkoxyamine initiator was subsequently employed to initiate the emulsion polymerization of n-butyl methacrylate with a small amount of styrene under mild conditions (85°C). Kinetic analysis indicates that the polymerizations exhibit the same behavior (i.e., the same reaction rates and the same level of control) as those reported in our previous work in the absence of silica under otherwise similar experimental conditions [Qiao et al. Macromolecules 2013, 46, 4285−4295]. This observation is fully consistent with a PISA process taking place at the silica surface. The resulting self-assembled block copolymers formed polymer nodules randomly distributed around the central silica spheres. Varying the macroinitiator concentration or the silica particle size enabled the successful formation of hybrid particles with dumbbell-, daisy-, or raspberry-like morphologies using this new surface-PISA process. ■ INTRODUCTIONColloidal particles with complex shapes such as triangles, pyramids, rods, cubes, nanodisks, star-like, peanuts and other sorts of exotic geometries have attracted considerable attention in the past few years. 1−4 Such complex particles with welldefined compositions and morphologies can find applications in many areas of colloid science and are very promising building blocks for the elaboration of functional advanced materials. 5−7 Among them, multipod-like particles with a controlled number of pods (e.g., dumbbells, dipods, tripods, and beyond) have been the subject of intensive research. 8−15 For instance, colloidal polymer−polymer dumbbells have been produced by controlled phase separation in seeded emulsion polymerization. 9−11 Colloidal polymeric clusters with a precisely defined geometry have been generated by confining latex particles to water-in-oil emulsion droplets and subsequent oil removala process pioneered by Velev et al. 12 in 1996 and further extended to a variety of colloidal systems 13−16 including inorganic particles 15 and binary mixtures of organic and inorganic colloids. 16 Organic/inorganic particles have received increasing interest in the recent literature. 17 Our group has been particularly active in this area, with special attention being focused on the synthesis of polymer/silica biphasic particles. 18−22 Such particles can be obtained by seeded-growth emulsion polymerization using methacryloxymethyltriethoxysilane (MMS) 18,19 or poly(ethylene oxide) methyl ether methacrylate (PEOMA) 20 functionalized silica particles as seeds. Depending on the reacti...

Organic–inorganic hybrid particles have many potential applications, but almost all research has been focused on hybrid particles with one kind of inorganic nanoparticle. This article presents a novel and facile preparation approach for raspberry‐like silica/polystyrene/silica multilayer hybrid particles via miniemulsion polymerization. In this method, larger, surface‐modified silica particles are first dispersed into monomer droplets to form a miniemulsion, and then raspberry‐like silica/polystyrene/silica multilayer hybrid particles are directly obtained when miniemulsion polymerization is performed in the presence of smaller, unmodified silica particles with 4‐vinylpyridine as an auxiliary monomer. Influential parameters such as the amount of 4‐vinylpyridine, the surfactant concentration, and the pH value of the system have been investigated. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1028–1037, 2007

A series of SiO2/poly(styrene‐co‐butyl acrylate) nanocomposite microspheres with various morphologies (e.g., multicore–shell, normal core–shell, and raspberry‐like) were synthesized via miniemulsion polymerization. The results showed that the morphology of the composite latex particles was strongly influenced by the presence or absence of the soft monomer (butyl acrylate), the particle sizes of the silica, and the emulsifier concentrations. The incorporation of the soft monomer helped in forming the multicore–shell structure. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3202–3209, 2006

No abstract

High performance Mg-8.2Gd-3.8Y-1.0Zn-0.4Zr alloy with high strength and excellent ductility has been successfully developed by hot extrusion. The effect of plate-shaped long period stacking ordered (LPSO) phases and solute-segregated stacking faults (SFs) on the dynamically recrystallization (DRX) behavior was analyzed. The plate-shaped LPSO phases stimulate the DRX by particle stimulated nucleation mechanism, leading to higher DRX ratio and weaker basal texture. While for the alloy with dense fine SFs inside the original grains, discontinuous DRX initially occurs at the original grain boundaries, and the DRX is obviously restricted. Consequently, alloy containing dense SFs exhibits higher strength but lower ductility compared with alloy with plated-shaped LPSO phases.

Organic-inorganic hybrid particles have many potential applications, but almost all of this research was focused on the hybrid particles containing one kind of inorganic nanoparticles. This paper presented a facile preparation method for SiO2/PS/TiO2 multilayer core-shell hybrid microspheres. In this approach, positively charged SiO2/PS core-shell hybrid particles were first synthesized by miniemulsion polymerization using cationic initiator and emulsifier. These positively charged SiO2/PS hybrid particles were mixed with tetra-n-butyl titanate for sol-gel reaction to directly form SiO2/PS/TiO2 multilayer core-shell hybrid microspheres. Some influencing parameters such as surfactant concentration, tetra-n-butyl titanate amount, and glacial acetic acid amount were investigated. TEM, TGA, and EDX analyses indicated that titania layers were successfully coated onto the surfaces of hybrid microspheres.