Superparamagnetic particles offer a new way to probe the kinetics of adhesive processes. Two different scenarios of physical adhesion are studied. The thermal activation of van der Waals adhesion is well described by an Arrhenius model. In contrast, it is necessary to go beyond the Arrhenius description to understand the thermal activation of bridging between colloidal particles by a polymer at equilibrium adsorbance. We show that polymer bridging requires some removal of adsorbed polymer and is strongly influenced by the proximity of a glass transition within the adsorbed polymer.

The rheological behavior of soybean oil emulsions stabilized by sodium caseinate is studied. While having a very low interfacial tension, these emulsions, when concentrated up to an oil volume fraction of 64%, have a very high elasticity. It is 30 times higher than those usually observed for surfactant-stabilized emulsions. We show that this high elasticity originates from the interfacial shear elasticity of the bilayer interface. So, sodium caseinate stabilized droplets can be regarded as droplets coated with a solid shell.

During the past decades, organic and inorganic colloids have been widely used for biological or biotechnological applications. In the last decade, colloidal organic / inorganic composites, namely super-paramagnetic particles, have constituted a real improvement for some of these applications. Very recently, we have developed a new way of using such colloidal composites in the fundamental domain of molecular recognition and in the closely linked but more industrial field of immunological diagnosis.Résumé -Colloïdes pour l'étude de la reconnaissance moléculaire. Au cours des décennies passées, les colloïdes organiques et inorganiques ont été largement mis à contribution pour des applications biologiques ou biotechnologiques. Lors des dix dernières années, les composites colloïdaux organique/inorganique , et précisément les particules superparamagnétiques, ont constitué une véritable amélioration dans le cadre de certaines de ces applications. Très récemment, nous avons développé une nouvelle méthode d'utilisation de tels composites colloïdaux dans le domaine de la reconnaissance moléculaire et dans celui, étroitement lié mais plus industriel, du diagnostic immunologique.