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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 38: Interfaces and Thin Films II

CPP 38.3: Vortrag

Donnerstag, 20. März 2025, 17:00–17:15, H38

Ion Specific Effects and Photo-Switching of Surfactants at Interfaces — •Dana Glikman and Björn Braunschweig — Institute of Physical Chemistry and Center for Soft Nanoscience, University of Münster, Busso-Peus-Str. 10, 48149 Münster (Germany)

Understanding surface charging and molecular structure changes at oil/water (O/W) interfaces in nanoemulsions is critical for enhancing colloidal properties. In previous work, we demonstrated that photo-switchable surfactants could modulate interfacial behavior. Specifically, we studied an arylazopyrazole (AAP) derivative that undergoes photoisomerization between E and less surface-active Z isomers. In nanoemulsions with droplets showing an average radius of 90 nm, no significant changes in drop size or ζ-potential were observed upon E/Z photo-isomerization. However, second-harmonic scattering (SHS) revealed substantial changes in surfactant coverage which were attributed to ion condensation at the interface [1]. In this contribution, we now focus on the role of specific ion effects and the structural influence of the surfactants’ head group. By systematically varying between Li, Na, and Cs cations and by using surfactants with different head group architectures, we aim to dissect the interplay between ionic specificity and head group structure. To study the adsorption of the surfactants at the interface, we are analyzing SHS profiles combined with measurements of the ζ-potential at the shear plane, in order to reveal a detailed mechanisms of ion-specific effects and ion condensation in these nanoemulsions. [1] Glikman et al. J. Am. Chem. Soc. 146, 8362 (2024).

Keywords: Specific Ion Effects; Nanoemulsions; Photoswitches