Regensburg 2016 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 61: Interfaces and Thin Films I (joint session CPP/DY, organized by CPP)

CPP 61.4: Vortrag

Donnerstag, 10. März 2016, 17:15–17:30, H51

Molecular Structure of Polyelectrolyte/Surfactant Mixtures with Tunable Electrostatic Interactions at Air-Water Interfaces — •Felix Schulze-Zachau and Björn Braunschweig — Institute of Particle Technology (LFG), Friedrich-Alexander University of Erlangen-Nürnberg (FAU), Cauerstrasse 4, 91058 Erlangen, Germany

Mixtures of poly(sodium 4-styrenesulfonate) (NaPSS) polyelectrolytes and cetyltrimethylammonium bromide (CTAB) surfactants were studied at the air/water interface with tensiometry, ellipsometry and vibrational SFG spectroscopy. Additionally, macroscopic foams from these mixtures were studied in order to relate information on the interfacial molecular structure and charging state to foam stability and foamability. At low NaPSS concentrations, hydrophobic PSS⁻/CTA⁺ complexes adsorb at air/water interfaces with co-adsorbed free CTA⁺ ions. The latter leads to relatively stable foams. For mixtures with equimolar concentrations, there is a significant rise in surface tension to values close to the tension of neat water that is accompanied by negligible foamabilities. However, SFG spectroscopy and ellipsometry provide evidence that PSS⁻/CTA⁺ complexes are at the interface with high coverage. Obviously, at these concentrations PSS⁻/CTA⁺ complexes are highly solvated at the interface but in a subsurface configuration with a covering water layer with free OH groups that give a clear signature in our SFG spectra. For excess NaPSS concentrations, surface adsorption is mainly determined by the molecular properties of PSS⁻ interfacial layers which provide good foamability and stability.