Berlin 2024 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 4: Interfaces and Thin Films
CPP 4.12: Vortrag
Montag, 18. März 2024, 12:30–12:45, H 0111
From X-ray reflectometry to surfactant surface coverage with the help of MD simulations — •Kay-Robert Dormann1, Joshua Reed1, Matej Kanduč2, Benno Liebchen1, and Emanuel Schneck1 — 1Institut für Physik kondensierter Materie, Technische Universität Darmstadt, Hochschulstr. 8, 64289 Darmstadt, Germany — 2Department of Theoretical Physics, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia
Adsorption of surfactants to fluid interfaces occurs in numerous technological and daily-life contexts. The surfactant surface coverage Γ governs important interface characteristics like tension, viscoelastic properties, or the stability of thin foam films. Direct measurements of Γ are therefore highly desirable but have remained challenging, especially for non-ionic surfactants without easily detectable (e.g., elemental) labels [1]. Here, we utilize atomistic MD simulations of surfactant-loaded air/water interfaces with defined Γ to obtain the associated interfacial electron density profiles. From these profiles, we compute theoretical X-ray reflectivity curves, which are then compared to experimental curves recorded with a conventional laboratory instrument. An important aspect in this procedure is the apparent interfacial roughness in experiments and simulations. For two non-ionic surfactants with previously verified force-fields [2,3] we demonstrate the suitability of this combination of experiments and simulations to deduce Γ as a function of the surfactant bulk concentration. [1] Kovalchuk et al., Langmuir 39, 3537 (2023). [2] Kanduč et al., J. Chem. Theory Comput. (2023). [3] Kanduč et al., J. Colloid Interf. Sci. 586, 588 (2021).