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Abstract:
The time scales of the p-nitrophenol (pNP) interfacial association at the curved surfactant monolayers of a dioctyl-sulfosuccinate (AOT) water-in-oil microemulsion system were identified and quantified using the Iodine Laser Temperature Jump (ILTJ) technique. The location of the solute (pNP) was monitored spectrophotometrically as a function of time, following a rapid (≈1μs) temperature perturbation of the system which shifted the partitioning of pNP between the water and oil phases. The characteristic time assigned to solute association and/or transport was measured to be in the range 0.1–1 ms. The equilibrium distribution of pNP was determined and used to identify the mechanism responsible for this relaxation time. Our preliminary results for the association of pNP from the aqueous phase to the curved surfactant interface and transport to the oil are consistent with estimates based on reported results for interfacial resistance offered by surfactants at planar interfaces. A model that accounts for mass-transfer between the water-surfactant-oil regions is proposed to describe the association and transport of species through the surfactant pseudophase and used to analyze the experimental characteristic times.
