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Organisation de nanoparticules dans des phases ordonnées de copolymères diblocs amphiphiles

Abstract : Poly(styrene)-block-poly(acrylic acid) diblock copolymers present a microphase separation and self-organize in a spherical, an hexagonal and a lamellar phase in a solide state. These nanostructures swell selectively in water and keep their long range order: water invades the PAA shells, but not the hydrophobic and glassy PS-cores. The period of the dispersed ordered hexagonal and lamellar phases then depends on the PAA ionization degree, controlled via the pH. The swelling in water of the structures is investigated using small-angle X-ray scattering (SAXS) and freeze-fracture transmission electron microscopy (FF-TEM). These properties of controlled swelling are used in the preparation of ordered nanocomposites of copolymersand mineral nanoparticles. This approach consists in a selective incorporation of the nanoparticles in the ordered PAA microdomains using water as medium. Using a simple model of polyelectrolyte brushes, we estimate the balance between the interaction and the confinement effects in the incorporation of nanoparticles depending on the parameters (pH, morphology, particle size). We experimentally confirm these results on composites containing silica and cerium oxide nanoparticles through the structural analysis of the dispersed hybrid systems as well as the final nanocomposites obtained after drying. We especially obtain well ordered lamellar structures containing up to 12% by volume of oxide nanoparticles. Such nanocomposites are promising for applications in functionnal materials.
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Benoit Maxit. Organisation de nanoparticules dans des phases ordonnées de copolymères diblocs amphiphiles. Matière Condensée [cond-mat]. Université Sciences et Technologies - Bordeaux I, 2007. Français. ⟨tel-00581646⟩

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