The Role of Diffusion in Dynamic Interfacial Tension Data: The Transition From Diffusion-Limited to Kinetic-Limited Dynamic

Tuesday, November 9, 2010: 4:35 PM
Canyon A (Hilton)
Nicolas Alvarez1, Lynn M. Walker1 and Shelley L. Anna2, (1)Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA, (2)Departments of Mechanical Engineering and Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA

Determining the dependence of dynamic interfacial tension on diffusion or kinetic transport is a long standing goal of surfactant research. Traditional methods rely on a square root dependence of early time data [1]. Using a newly derived and validated spherical diffusion-limited timescale [2], we have determined a scaling argument to quantitatively assess the dependence of dynamic data on diffusion and kinetic transport properties. This study presents the usefulness of this scaling using data obtained from the literature as well as measurements made using a novel device designed to measure dynamic surface tension at microscopic interfaces, denoted a microtensiometer. Specifically, we compare the dynamic response of a given surfactant species at the air-water and oil-water interface to illustrate the sensitivity and usefulness of this approach. This method is general to any type of surface active species (i.e. ions, surfactants, polyelectrolytes, and amphiphilic polymers) and requires knowledge of only an appropriate isotherm. More specifically this methodology reduces the ambiguity of choosing a model to describe surfactant dynamics and in some cases results in a quantitative measure of the adsorption rate constant.

[1] S.N. Moorkanikkara and D. Blankschtein, Journal of Colloid and Interface Science, 296, 2 (2006). [2] N.J. Alvarez, L.M. Walker, and S.L. Anna, Submitted: Physical Review E, (2010).

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See more of this Session: Fundamentals of Interfacial Phenomena III
See more of this Group/Topical: Engineering Sciences and Fundamentals