Papers by elodie Bourgeat
Journal of Nanoscience and Nanotechnology, 2006
Silica/polystyrene nanocomposite particles with different morphologies were synthesized through e... more Silica/polystyrene nanocomposite particles with different morphologies were synthesized through emulsion polymerization of styrene in the presence of silica particles previously modified by-methacryloxypropyltrimethoxysilane (MPS). Grafting of the silane molecule was performed by direct addition of MPS to the aqueous silica suspension in the presence of an anionic surfactant under basic conditions. The MPS grafting density on the silica surface was determined using the depletion method and plotted against the initial MPS concentration. The influence of the MPS grafting density, the silica particles size and concentration and the nature of the surfactant on the polymerization kinetics and the particles morphology was investigated. When the polymerization was performed in the presence of an anionic surfactant, transmission electron microscopy images showed the formation of polymer spheres around silica for MPS grafting densities lower than typically 1 mole•m −2 while the conversion versus time curves indicated a strong acceleration effect under such conditions. In contrast, polymerizations performed in the presence of a larger amount of MPS moieties or in the presence of a non ionic emulsifier resulted in the formation of "excentered" core-shell morphologies and lower polymerization rates. The paper identifies the parameters that allow to control particles morphology and polymerization kinetics and describes the mechanism of formation of the nanocomposite colloids.
Dans la mythologie romaine, Janus est un dieu à une tête mais avec deux visages opposés. Par anal... more Dans la mythologie romaine, Janus est un dieu à une tête mais avec deux visages opposés. Par analogie, le terme " Janus " qualifie tout objet dissymétrique, tel qu'une particule sphérique dont les deux hémisphères seraient chimiquement différents. Très attendues sur le plan de leurs propriétés et de leurs applications, ces particules Janus seraient en outre des briques élémentaires essentielles dans la réalisation future d'assemblages supraparticulaires. L'objectif de cet article est de mettre en valeur les efforts souvent très imaginatifs que les chimistes continuent de fournir pour leur synthèse et leur caractérisation.
Le concept de molécules colloïdales a été évoqué pour la première fois par van Blaaderen en 2003 ... more Le concept de molécules colloïdales a été évoqué pour la première fois par van Blaaderen en 2003 pour décrire de petits agrégats supraparticulaires dont l'assemblage pourrait conduire à des matériaux complexes aux propriétés originales, notamment dans le domaine de l'optique. Cet article décrit les travaux qui se sont avérés les plus pertinents pour élaborer ces premières briques élémentaires.
Journal of Nanomaterials, 2006
Polystyrene (PS) chains with molecular weights comprised between 8000 and 64000g⋅mol-1and narrow ... more Polystyrene (PS) chains with molecular weights comprised between 8000 and 64000g⋅mol-1and narrow polydispersities were grown from the surface of silica nanoparticles (Aerosil A200 fumed silica and Stöber silica, resp.) through nitroxide-mediated polymerization (NMP). Alkoxyamine initiators based on N-tert-butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide (DEPN) and carrying a terminal functional group have been synthesized in situ and grafted to the silica surface. The resulting grafted alkoxyamines have been employed to initiate the growth of polystyrene chains from the inorganic surface. The maximum grafting density of the surface-tethered PS chains was estimated and seemed to be limited by initiator confinement at the interface. Then, the PS-grafted Stöber silica nanoparticles were entrapped inside latex particles via miniemulsion polymerization. Transmission electron microscopy indicated the successful formation of silica-polystyrene core-shell particles.
MRS Proceedings, 2004
ABSTRACTColloidal particles with a controlled morphology combining both organic and inorganic par... more ABSTRACTColloidal 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.
MRS Proceedings, 2005
One area of particular effort recently is the use of colloidal particles as precursors in enginee... more One area of particular effort recently is the use of colloidal particles as precursors in engineering new materials. Nevertheless, these particles are nearly always spheres. This places limitations on the structures that can be built, especially in making photonic-bandgap materials. Therefore, it is a great challenge to create new colloids with an original shape, i.e. different from the sphere, in a controllable manner.We present here an original approach to create hybrid organic-inorganic colloidal particles with a perfect controlled shape. The synthetic route of these structures, which are composed of spherical silica spheres surrounded by a varying number of polystyrene beads, consists in the emulsion polymerization of styrene in presence of silica particles, which had been surface-modified by a coupling agent containing polymerizable groups.The influence of the size of the silica particle and of the nature of the coupling agent on the resulting colloidal particles morphologies w...
Polymer Chemistry, 2014
Nanosized dumbbell- and snowman-like P(Sty-co-BuA)/silica particles have been successfully synthe... more Nanosized dumbbell- and snowman-like P(Sty-co-BuA)/silica particles have been successfully synthesized via emulsion polymerization.
Polymer International, 2003
... Scheme 1. Schematic representation of the encapsulation reaction of organic pigments through ... more ... Scheme 1. Schematic representation of the encapsulation reaction of organic pigments through miniemulsion polymerization. thumbnail image. ... Organic pigments have a wide range of commercial applications in coatings, printing and paint industries. ...
Macromolecular Symposia, 2007
Polymer/silica and polymer/Laponite nanocomposite colloids with various morphologies have been el... more Polymer/silica and polymer/Laponite nanocomposite colloids with various morphologies have been elaborated through emulsion polymerization using a polymerizable organosilane (route I) and a methyl methacrylate-terminated macromonomer (route II) as coupling agents. Depending on the synthetic strategy and on the nature of the mineral particles, either core-shell, raspberry-like, multipod-like, currant bun or inverted core-shell morphologies (the mineral forming the shell) were achieved. Beyond the control of particle shape, we have demonstrated that some of the polymerizations exhibited particular kinetics behaviors which could be correlated to the mechanism of formation of the composite particles. Interestingly, conversion versus time curves of a series of soap free polymerizations performed in the presence of the macromonomer showed a significant increase in the polymerization rate with increasing the inorganic particles concentration. Characterization of the composite latexes by transmission electron microscopy showed that the mineral was located at the surface of the latex spheres and participated therefore to their stabilization. The higher the amount of inorganic particles, the lower the particles size and the higher the polymerization rate.
Macromolecular Symposia, 2005
Polymer latex particles were synthesized in the presence of inorganic particles, which had been o... more Polymer latex particles were synthesized in the presence of inorganic particles, which had been organically-modified to promote favorable interactions with growing macromolecules. The organic modification was performed using three different routes: (1) surface covalent grafting of vinyl trialkoxysilanes, (2) surface adsorption of polyethylene glycol-based macromonomers, and (3) bulk modification through ion exchange with cationic monomers or cationic initiators. Two types of mineral particles were studied: commercial and self-prepared silica particles (with diameters from 80 nm to 1 mm), and commercial laponite clay particles with a cation exchange capacity of 0.75 meq Á g À1. Emulsion polymerization was performed in the presence of styrene or butyl acrylate monomers. The morphologies of the nanocomposite particles were observed by (cryogenic) transmission electron microscopy and correlated to the organic modification procedure.
Macromolecular Materials and Engineering, 2007
Journal of Materials Chemistry, 2005
Because the Roman god Janus was usually represented with two heads placed back to back, the term ... more Because the Roman god Janus was usually represented with two heads placed back to back, the term Janus is used for the description of particles whose surfaces of both hemispheres are different from a chemical point of view. So, they could be used as building blocks for ...
Journal of Materials Chemistry, 2009
Original planar biphasic colloids are obtained by (i) using a growth-seeded emulsion polymerizati... more Original planar biphasic colloids are obtained by (i) using a growth-seeded emulsion polymerization process where a controlled number of polystyrene nodules are able to nucleate and grow on submicronic silica seeds to form multipods and (ii) shaping these multipods on a planar ...
univ-ubs.fr
RESUME: Des nanoparticules biphasiques silice/polystyrène sont obtenues selon un procédé original... more RESUME: Des nanoparticules biphasiques silice/polystyrène sont obtenues selon un procédé original de polymérisation en émulsion du styrène en présence de particules silice colloïdale utilisées comme semences. La morphologie des objets dépend largement des ...
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2006
Colloidal particles with a controlled morphology combining both organic and inorganic parts were ... more Colloidal particles with a controlled morphology combining both organic and inorganic parts were synthesized through a seeded emulsion polymerization process. Silica seed particles (from 100 to 400 nm in diameter) were first surface-modified by the adsorption of an oxyethylenebased 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. While varying different experimental parameters, we have demonstrated that the ratio between the number of silica seeds and the number of growing nodules is a key parameter to control the morphology of the final hybrid nanoparticles.
Chemistry of Materials, 2005
Colloidal particles with a controlled morphology combining both organic and inorganic parts were ... more 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 were first surface-modified by adsorption of an oxyethylene-based ...
Chemical Communications, 2005
univ-ubs.fr
... Ainsi, des particules à structure « cur/écorce » dans lesquelles les plaquettes d'argil... more ... Ainsi, des particules à structure « cur/écorce » dans lesquelles les plaquettes d'argile viennent décorer la surface des billes de ... C. Bartholome, E. Beyou, E. Bourgeat-Lami, P. Chaumont, N. Zydowicz, Nitroxide-mediated polymerizations from silica nanoparticles surfaces : graft ...
Angewandte Chemie International Edition, 2009
Uploads
Papers by elodie Bourgeat