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Research activities:

Rheophysics (2002 - present) :

 

We have built two Couette shear cells located in our Institute and by the Swing beamline of SOLEIL. These devices allow us to study the structures of complex fluids under shear by X-ray scattering. We are particularly interested in the flow properties of suspensions of nanometric clay platelets that are commonly used in the industry.

 

Hybrid systems (2006- present) :

 

We have recently formulated lamellar liquid-crystalline phases doped with mineral nanoparticles and we study their structural and dynamic properties. We thus managed to obtain mesophases that display quite original properties..

 

Mineral liquid crystals (1992- present) :

 

Colloidal suspensions of anisotropic nanoparticles (rods, ribbons, platelets …) form liquid-crystalline phases that can be nematic, smectic and columnar. These suspensions combine the properties of anisotropy and fluidity that are typical of liquid crystals with the electronic properties (magnetism, conductivity …) of minerals.

 

Suspensions of biopolymers (2002- present) :

 

Numerous water-soluble polymers (or that may be solubilised), such as actin, chitin, or collagen, can be found in Nature. We study the liquid-crystalline organizations of these suspensions and their influence on the structures of related biomaterials.

 

Mesoporous silicas (1998-2003) :

 

Silica-based materials, that display a controlled porosity organised on a 2D hexagonal lattice, can be produced by condensation of silica precursors around the cylindrical micelles of triblock copolymer surfactants (SBA-15). We have studied their peculiar porosity and processed these materials as monoliths and fibers.

 

Gels from lamellar L mesophases (1994-2001) :

 

Inserting hydrosoluble polymers, bearing an (or two) hydrophobic anchor at their ends, into the phospholipid membranes of an L phase leads to an unusual gelation phenomenon upon dilution. This phenomenon is due to the proliferation of topological defects stabilized by these macromolecules.

 

Liquid-crystalline polymers (1984-1993) :

 

By polymerizing head to tail liquid-crystalline molecules (“main-chain” polymers) or by grafting them onto a preformed skeleton (“side-chain” polymers), one can produce materials that have the properties of polymers (Tg) and liquid crystals. We have studied their molecular organization (polymer conformation and localisation) and some of their physical properties (defects, flow-alignment).

 

Ionic discotic liquid crystals (1983-1990) :

 

Disc-like liquid-crystalline molecules very often stack in columns organized on a 2-dimensional lattice; usually, these molecules are neutral. The search for conducting liquid crystals has led to the synthesis of ionic liquid crystals that can display mesophases even with very short side-chains, thanks to counter-ions disorder.

From the instrumental point of view, my research activities heavily involve X-ray (and sometimes neutron) scattering in our Institute as well as at synchrotron radiation facilities (ESRF, SOLEIL). I also use polarized-light microscopy and rheology, and I often examine the influence on complex fluids of magnetic and electric fields.