(730c) Tween 80 and Aerosol-OT Adsorption Behavior At An OIL-Aqueous Interface

Dispersants contain a number of different surface active components.  We have characterized the impact of two primary components on the adsorption of each other at oil-water interfaces. Pre-adsorbed layers of Tween-80 are found to inhibit adsorption of AOT molecules at the interface.  The mechanism appears to be due both to reduction of available interfacial area for AOT molecules, and generation of charge in the layers of nonionic Tween-80 that causes electrostatic repulsion for the negatively charged AOT.  Once adsorbed into a mixed layer at the interface, the AOT and Tween-80 molecules interact at the interface, as determined by the nature of the dilatational viscosity and elasticity of the interfaces. A mixed transport and surface reaction model was developed and used to fit adsorption rate constants for AOT to the Tween coated interfaces. Overall, these experiments and analysis serve to describe important interactions that might be expected to play a role in the transport properties of dispersant mixtures to oil-aqueous interfaces. The experimental techniques and analysis approach used in this study are applicable to any binary mixture of surfactant systems where one component adsorbs irreversibly, and also for elucidating the effects of charged surfactant layers. This information is critical for effective dispersant design, as well as for emulsion systems containing multiple surfactant components.