HYDRODYNAMIC MODES OF SOLUBLE SURFACTANT FILMS

Soluble surfactants in suspended soap films are distributed on the sur face monolayers and inside the films. We study theoretically the effec ts of the dynamics redistribution of surfactants between these two pla ces on the Linearized soap film hydrodynamics. The interchange of surf actants can be incorporated into the existing hydrodynamic analysis as an effective complex surface modulus. The main effects are on Marango ni modes and the peristaltic modes. The presence of micelles at high s urfactant concentration can be easily included for submegahertz freque ncies provided the surfactant solution has a fast micelle forming/brea king kinetics. The effects of any intrinsic surface viscosities in the monolayers are briefly discussed.