Résumé
Foams are ubiquitous in daily life. This fluid, however, never reaches thermodynamic equilibrium and is constantly undergoing structural change until the fluid's gas and liquid components are separated. Physical and chemical phenomena occur at various times and scales, which makes it challenging to correlate how the foam ages. However, it is figuring out how to adjust its formulation so that it can regulate both its viscoelastic characteristics and its lifespan in accordance with the necessary uses. It is important to describe a created foam in its whole, including the size of the supramolecular self-assemblies, the inter-bubble layer, and the bubbles (on a millimeter or centimeter scale) (at the nanometre scale). To track the multi-scale evolution of a developing foam, it is necessary to use a variety of experimental methodologies simultaneously and "in operando". In order to overcome this difficulty, a special cell has been created to demonstrate, first, the potential data collection as a function of time of a free-draining foam investigated utilizing simultaneously small angle neutron scattering (SANS at ILL/D33), electrical conductivity, and optical imaging. The combination of the findings and the creation of a specific analysis code allowed us to follow the kinetics of the different surfaces independently of the inter-bubble films, the Plateau border, and their time lag, and to describe a disjunction pressure isotherm as a function of the average film thickness within an evolving foam [1]. This novel approach was employed in a study that examined the stability of a foam made with an ethoxylated fatty alcohol as a non-ionic surfactant and in the presence of either ionic charges supplied by either a second ionic surfactant (sodium dodecyl sulfate) or nanometer-sized ions (nano-ions) with low charge density. In the first instance, the ionic species stabilizes the foam by attaching to the surfactant film via a hydrophobic interaction with the help of its fatty chain, whereas in the second instance, the association of the nano-ions with the surfactant monolayer is brought about by a potent (super)chaotropic effect. [2,3]. Despite the fact that both species tend to lengthen the lifetime of a non-ionic foam, minute similarities and differences are highlighted and explored by correlating findings, particularly macro- and nanometric quantities, and by linking them to the rheological response of the interfacial layers. Very recently, the study of foam and nano-ions has opened up exciting possibilities for extraction separation applications using the concept of superchaotropic flotation. [4]