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Open AccessFeature PaperArticle

Dynamic Properties of Mixed Cationic/Nonionic Adsorbed Layers at the N-Hexane/Water Interface: Capillary Pressure Experiments Under Low Gravity Conditions

1
Institute of Condensed Matter Chemistry and Technologies for Energy, 16149 Genoa, Italy
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Institute of Biocolloid Chemistry, 03142 Kiev, Ukraine
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Department of Colloid Chemistry, St. Petersburg State University, 198504 St. Petersburg, Russia
4
Max Planck Institute of Colloids and Interfaces, 14424 Potsdam/Golm, Germany
*
Author to whom correspondence should be addressed.
Colloids Interfaces 2018, 2(4), 53; https://doi.org/10.3390/colloids2040053
Received: 4 October 2018 / Revised: 26 October 2018 / Accepted: 29 October 2018 / Published: 2 November 2018
Capillary pressure experiments are performed in microgravity conditions on board the International Space Station to quantify the dynamic interfacial behavior of mixed adsorption layers of TTAB and C13DMPO at the water/hexane interface. While the non-ionic surfactant C13DMPO is soluble in both bulk phases, water and hexane, the cationic surfactant TTAB is only soluble in the aqueous phase. The interfacial layer is thus formed by TTAB molecules adsorbing from the aqueous phase while the C13DMPO molecules adsorb from the aqueous phase, and transfer partially into the hexane phase until both the equilibrium of adsorption and the distribution between the two adjacent liquid phases is established. The experimental constrains as well as all possible influencing parameters, such as interfacial and bulk phase compressibility, interfacial curvature, calibration of pressure and absolute geometry size, are discussed in detail. The experimental results in terms of the dilational interfacial viscoelasticity of the mixed adsorption layers in a wide range of oscillation frequencies show that the existing theoretical background had to be extended in order to consider the effect of transfer of the non-ionic surfactant across the interface, and the curvature of the water/hexane interface. A good qualitative agreement between theory and experiment was obtained, however, for a quantitative comparison, additional accurate information on the adsorption isotherms and diffusion coefficients of the two studied surfactants in water and hexane, alone and in a mixed system, are required. View Full-Text
Keywords: adsorption of mixed surfactant; water/hexane interface; capillary pressure tensiometry; dilational viscoelasticity; drop oscillations; microgravity adsorption of mixed surfactant; water/hexane interface; capillary pressure tensiometry; dilational viscoelasticity; drop oscillations; microgravity
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Loglio, G.; Kovalchuk, V.I.; Bykov, A.G.; Ferrari, M.; Krägel, J.; Liggieri, L.; Miller, R.; Noskov, B.A.; Pandolfini, P.; Ravera, F.; Santini, E. Dynamic Properties of Mixed Cationic/Nonionic Adsorbed Layers at the N-Hexane/Water Interface: Capillary Pressure Experiments Under Low Gravity Conditions. Colloids Interfaces 2018, 2, 53.

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