title: Out of equilibrium divergence of dissipation in an oscillating bubble coated by surfactants.
abstract: We report measurements of the relaxation and resonance frequency of forced oscillating bubbles covered by a layer of surface-active molecules, the anionic surfactant sodium dodecyl sulfate (SDS). Less systematic investigations have been also carried out on neutral and cationic surfactants. A divergence of the viscous damping is observed at a very low bulk concentration. Subtle variations in the resonance peak are also measured. Bubble oscillations are driven by an electric field and measured with a sensitive interferometric technique. Results are interpreted with a model which takes care of the coupling between the dynamics of fluid surface oscillations and the properties of a surfactant monolayer in the vicinity of the phase transition from a gas-like distribution to a liquid-like assembly (the so-called gas-LE transition). Important charge effects are also considered. The basic assumptions of the model (cooperative adsorption of the surfactant at the air-water interface and coupling between the shape of the deformed surface and the local surfactant concentration) have been fully confirmed by extensive coarse-grained molecular dynamics simulations on model systems.
authors: CNR-IPCF, Viale Ferdinando Stagno d'Alcontres, 37, 98158 Messina, Italy.
authors: Mario
authors: M
authors: Corti
authors: Martina
authors: M
authors: Pannuzzo
authors: Antonio
authors: A
authors: Raudino
mesh_terms: D005740:Gases / Q000737:chemistry; D056004:Molecular Dynamics Simulation; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry*; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D005740:Gases; D013501:Surface-Active Agents; D012967:Sodium Dodecyl Sulfate