(92b) Interfacial Properties and Interactions of Emulsion Drops Stabilized by Mixtures of Surfactants

Emulsions of silicone oils are common surface modifiers in consumer care products . Droplet charge plays a critical role in determining the interactions with a substrate (hair, fibers etc.)  In this talk, we present an experimental investigation of the interfacial properties of non-ionic surfactant stabilized oil-in-water emulsions of silicones.  Electrophoresis of droplets as a function of different solution compositions is studied.  We observe adsorption of ionic surfactants from solution, which is characterized by neutralization of charge followed by charge reversal of the emulsion droplet.  Furthermore, the change in the droplet surface charge density due to the adsorption of ionic surfactants can be used to characterize the change in the surfactant concentration at the drop interface.  The insights gained from this experimental work are used to calculate the emulsion drop-drop and drop-substrate interactions, which are then verified by laser tweezers interaction measurements.  This can quantitatively address the phenomena of deposition of emulsion droplets at solid substrate.