SANS studies of hybrid nanosystems

Abstract

The soft matter group of LLB is centered on Small Angle Neutron Scattering (SANS). It is in charge of three classical SANS facilities (one annular detector and two XY detectors) and one polarized neutron SANS, and is developing a new USANS diffractometer. The group is also connected withneutron reflectivity, and to a lesser extent to inelastic scattering (spin echo, time of flight). In the field of soft matter, the expertise has been for many years focused on polymer solutions (neutral and charged), adsorbed polymers, polymer melts, and liquid crystalline polymers, witha focus on the effect of mechanical deformation (“rheo-SANS”). More recently, such deformation effects have been studied also on polymer latex films and latex-silica composites. We have chosento present this work here, which is at the boundary between polymer and colloid science, since interactions between silica particles in the films are involved and control partly the reinforcement of the polymer film. We will balance this example with another, the case of particles dispersed inside aqueous clays gels: Here, the particles are magnetic and play the role of probes, notinfluencing the properties of the material, but allowing an understanding of its properties, in particular the mechanical ones. Both systems are hybrid materials for which SANS is useful. For maghemite-clay mixtures, the contrast-matching method with a mixture of normal and deuterated water allows one to separate the different correlations: As usual, SANS is a powerful tool for thestudy of ternary systems. For composite films, the case of silica particles covered by polymer is under development; in this situation, labeling the grafted polymer will also give information unique to SANS.