کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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608777 | 880608 | 2011 | 6 صفحه PDF | دانلود رایگان |

Detailed surfactant transport studies have typically been restricted to the air–water interface. This is mainly due to the lack of experimental devices and techniques available to study liquid–liquid interfaces. As a result, there is a lack of relevant data and understanding of surfactant behavior in microfluidic studies and emulsion applications. Using a novel shape fitting algorithm for a pendant drop capable of handling fluids of similar densities, i.e. low Bond numbers, we measure the dynamic surface tension as a function of bulk surfactant concentration at the silicone oil–water interface for a homologous series of CiE8 nonionic surfactants. We show that the isotherms governing equilibrium at the oil–water and air–water interfaces are very different. Using a scaling analysis comparing two governing mass transport timescales, we demonstrate that there exists a transition from diffusion-limited to kinetic-limited dynamics at the silicone oil–water interface. Adsorption rate constants are determined from a one parameter nonlinear fit to dynamic surface tension data. These results demonstrate that the dynamics of interfacial transport are highly dependent on the immiscible fluids that form the interface.
A scaling analysis is used to determine whether dynamic surface tension experiments exhibit diffusion-limited or kinetic-limited transport. If diffusion-limited, the equilibration timescale follows scaling expected for diffusion in a spherical geometry (solid line). If kinetic-limited, the timescale deviates from the diffusion scaling. Identifying when kinetics are relevant aids in correctly analyzing dynamic surface tension data to determine kinetic rate constants.Figure optionsDownload high-quality image (35 K)Download as PowerPoint slideResearch highlights
► Scaling arguments determine relevant transport mechanisms for surface tension evolution.
► Diffusion-limited dynamics aid in fitting isotherm parameters.
► Adsorption rate constant decreases with increasing alkane tail length.
Journal: Journal of Colloid and Interface Science - Volume 355, Issue 1, 1 March 2011, Pages 231–236