(541b) Using Electric Fields to Manipulate Surfactant Transport to Oil-Water Interfaces

Control and characterization of the transport of surfactants to oil-water interfaces is a key aspect to formulation design. The transport of surfactant from bulk to a fluid-fluid interface has been well studied and is known to be a function of bulk concentration, isotherm, local convection and interface geometry. The impact of electric fields has not been studied. Here, we quantify the transport of oil soluble surfactants to oil-water interfaces using a microscale capillary tensiometer platform, under a D.C. electric field. Dynamic interfacial tension is measured as a function of the electric field strength for two systems – a polyisobutylene succinimide surfactant (OLOA 11000) at the Isopar-water interface, and a triblock polyethylene oxide-polypropylene oxide-polyethylene oxide surfactant (Pluronic L64) at the silicone oil-water interface. Surfactant transport is enhanced under electric field for OLOA in Isopar, and is not affected by the field for Pluronic in silicone oil. Electrical conductivity measurements reveal that the electro-migration of charge carriers in Isopar on addition of OLOA is responsible for the accelerated transport. Notably, this enhanced transport can be precisely tuned by altering the field strength. Our work establishes electric fields as a new parameter to tune surfactant transport to oil-water interfaces.