Dresden 2020 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 25: Interfaces and Thin Films II (joint session CPP/DY/O)

DY 25.3: Talk

Tuesday, March 17, 2020, 10:15–10:30, ZEU 260

Relation between stability and interfacial structure of polyelectrolyte containing foam films — •Larissa Braun and Regine von Klitzing — TU Darmstadt, Darmstadt, Germany

For many industrial applications foams of oppositely charged polyelectrolyte/surfactant-mixtures are of high impact, as they form surface active complexes.

Extensive research on such mixtures was already performed^[1,2] but the influence of the ionic strength is still unclear.

This work focuses on the influence of added LiBr on foam films of mixtures of the anionic polyelectrolyte sPSO2-220 (similar to PSS but stiffer) with the cationic surfactant C14TAB. Therefore, disjoining pressure isotherms were measured with a fixed C14TAB concentration and a variable polyelectrolyte concentration.

Different stability regimes were identified. Already a low salt concentration of 10^-4 M leads to a considerably less stable foam films regarding the maximum disjoining pressure. An unexpected formation of an unstable Newton Black Film was found at this low salt concentration. Higher salt concentrations will also be considered. These findings will be correlated with the surface excesses of both compounds which can be separated from each other by neutron reflectometry measurements.

[1] N. Kristen, A. Vüllings, A. Laschewsky, R. Miller, R. v. Klitzing, Langmuir, 2010, 12, 9321-9327. [2] M. Uhlig, R. Miller, R. v. Klitzing, Phys. Chem. Chem. Phys., 2016, 18, 18414-18423