Connectivity of the Hexagonal, Cubic, and Isotropic Phases of the C12EO6/H2O Lyotropic Mixture Investigated by Tracer Diffusion and X-ray Scattering

The connectivity of the hydrophobic medium in the nonionic binary system C12EO6/H2O is studied by monitoring the diffusion constants of tracer molecules at the transition between the hexagonal mesophase and the fluid isotropic phase. The increase in the transverse diffusion coefficient on approaching the isotropic phase reveals the proliferation of bridgelike defects connecting the surfactant cylinders. This suggests that the isotropic phase has a highly connected structure. Indeed, we find similar diffusion coefficients in the isotropic and cubic bicontinuous phases. The temperature dependence of the lattice parameter in the hexagonal phase confirms the change in connectivity close to the hexagonal-isotropic transition. Finally, an X-ray investigation of the isotropic phase shows that its structure is locally similar to that of the hexagonal phase

Etude de transition de phase vers les phases cubiques des systèmes eau/surfactant.

Ce travail a été consacré aux phases cubiques bicontinues dans les systèmes tensioactifs/eau. Plus particulièrement, deux transitions de phases vers une phase cubique bicontinue de groupe d'espace Ia3d ont été étudiées, en partant soit d'une phase hexagonale 2D, soit d'une phase lamellaire. En combinant des résultats expérimentaux de diffusion des rayons X, il a été possible d'établir des modèles géométriques décrivant la transformation de l'arrangement des aggrégats micellaires lors de ces transitions de phase.This work has been devoted to bicontinuous cubic phases in surfactant / water systems.;Two phase transitions to a bicontinuous cubic phase of space group Ia3d have been studied, starting either from a 2D hexagonal phase or from a lamellar phase. By combining experimental X-ray scattering results, it has been possible to establish geometric models describing the transformation of the arrangement of the micellar aggregates for these phase transitions

Nanocasting, templated syntheses and structural studies of manganese oxide nanoparticles nucleated in the pores of ordered mesoporous silicas (SBA-15)

International audienc

Epsilon-Fe 2 O 3 Nanocrystals inside Mesoporous Silicas with Tailored Morphologies of Rod, Platelet and Donut

International audienc

Macroscopic Magnetic Anisotropy Induced by the Combined Control of Size, Shape and Organization of NiFe Prussian Blue Analog Nanoparticles in an Ordered Mesoporous Silica Monolith

International audienceIntegration of coordination polymers and metal–organic frameworks into real applications requires a processing step at the nanoscale. However, their synthesis in the form of nanoparticles with controlled size, shape and organization remains a challenge faced by diverse scientific communities. Ordered mesoporous silica monolith with 2D‐hexagonal structure of the mesopores is used to form ferromagnetic NiFe Prussian blue analog (PBA) nanoparticles with anisotropic shape. The PBA nanowires formed within the nanochannels of the monolith are made of single chains of nanocrystals. Furthermore, when using an ordered mesoporous silica monolith instead of the more frequently used mesoporous powders a parallel organization of the pores is achieved over whole macroscopic fragments of the monolith. A 1×1×1 mm3 fragment of monolith exhibits a remarkably strong anisotropy in its magnetic properties, arising from unprecedented magnetic dipolar interaction along the chains of coordination nanocrystals, which is spread to the macroscopic scale thanks to the long‐range organization of the pores. As various confined chemistries can be developed within the ordered porosity of such monolith, this tool opens up new opportunities for the development of original nanostructured materials exhibiting anisotropy in their properties at the macroscopic scale