From Raspberry-like to Dumbbell-like Hybrid Colloids through Surface-assisted Nucleation and Growth of Polystyrene Nodul
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From Raspberry-like to Dumbbell-like Hybrid Colloids through Surface-assisted Nucleation and Growth of Polystyrene Nodules onto Macromonomer-modified Silica Nanoparticles Etienne Duguet1, Stéphane Reculusa2, Adeline Perro1,2, Céline Poncet-Legrand1,2, Serge Ravaine2, Elodie Bourgeat-Lami3 and Christophe Mingotaud4 1 Institut de Chimie de la Matière Condensée de Bordeaux, CNRS, Université Bordeaux-1, 87 avenue du Docteur Schweitzer, F-33608 Pessac, France 2 Centre de Recherche Paul Pascal, CNRS, Université Bordeaux-1, 115 avenue du Docteur Schweitzer, F-33608 Pessac, France 3 Laboratoire de Chimie et des Procédés de Polymérisation, CPE, CNRS, 43 boulevard du 11 novembre, BP 2077, F-69616 Villeurbanne, France 4 Laboratoire des Interactions Moléculaires et Réactivité Chimique et Photochimique, Université Paul Sabatier, CNRS, 118 route de Narbonne, F-31062 Toulouse, France ABSTRACT Colloidal particles with a controlled morphology combining both organic and inorganic parts were synthesized through a seeded emulsion polymerization process. Silica seed particles (from 50 to 150 nm in diameter) were first surface-modified by the adsorption of an oxyethylene-based macromonomer. Then, emulsion polymerization of styrene was carried out in presence of these particles, the formation of polystyrene nodules being highly favored at the silica surface in such conditions. The ratio between the number of silica seeds and the number of growing polystyrene nodules appeared to be one of the key parameters to control the morphology of the final hybrid nanoparticles. When this ratio is close to 1, original hybrid dumbbell-like nanoparticles were mainly obtained. INTRODUCTION In the past few years, a lot of work has been done in the field of colloidal hybrid particles made of materials of different compositions [1-3]. As a standard example, core-shell particles consisting of an inorganic core surrounded with an organic shell are currently produced and the range of materials available to get such morphologies is wide [4]. Raspberry-like morphologies have also been frequently reported [5-9]. Today, much attention is devoted to the elaboration of colloidal nanoparticles with tuneable shapes. Yin and Xia have first assembled monodispersed polymer beads by physical confinement in the cylindric holes patterned in a thin film of photoresist [10]. Later, Manoharan et al. have reported a method based on the drying of oil-in-water emulsion droplets containing spherical polystyrene colloids, resulting in the formation of colloidal clusters with 2, 3 and up to 15 colloids [11]. Following a similar strategy, Yi et al. have extended this process to other monophasic systems, either still polymeric (based on polymethylmethacrylate particles) or fully inorganic (hydrophobic silica clusters) [12]. In fact, the synthesis of hybrid colloidal assemblies has been first reported by Xia et al. with the successful formation of hetero-aggregates of spherical colloids using a principle almost identical to their previous work [13]. However, the association be
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