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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 24: Poster Session I

CPP 24.13: Poster

Montag, 16. März 2020, 17:30–19:30, P3

Adsorption of Dodecyl Sulfonate Surfactants and Alkali Ions at Extended and Nanoscopic Oil/Water Interfaces — •Dana Glikman, Eric Weißenborn, and Björn Braunschweig — Institute of Physical Chemistry and Center for Soft Nanoscience, Corrensstr. 28/30, 48149 Münster, Germany

Emulsions find many applications in different everyday life and industrial applications. However, a complete molecular-level understanding of the soft oil/water interface inside emulsions is still missing, but is prerequisite for targeted manipulation of emulsions. In this contribution, we report on the influence of anionic dodecyl sulfate (DS^-) surfactants and their counter ions (Li⁺, Na⁺, Cs⁺) at the extended- and nanoscopic hexadecane/water interface. In order to study the oil/water interface as a function of surfactant concentration and ionic strength on different length scales, we have applied a thin-film pressure balance and the captive bubble method for extended surface, but also recorded the zeta-potential and second-harmonic light scattering (SHS) profiles from nanoscopic oil drops. Due to the higher affinity of DS^- to oil, the surface pressure is higher at the oil/water interface than at the air/water interface. Nevertheless, we find similar trends for the alkali cations at the oil/water interface as for the air/water interface: in dependence on the counter ion, the maximal surface excess of DS^- decreases with decreasing ion size (Cs⁺ > Na⁺ > Li⁺). In addition, the zeta-potential of nanoemulsions is for NaDS more negative than for CsDS, which is corroborated by SHS experiments that can address the double-layer potential directly.