Dresden 2017 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 51: Poster: Charged Soft Matter, Polyelectrolytes, Ionic Liquids
CPP 51.8: Poster
Wednesday, March 22, 2017, 18:30–21:00, P3
Specific Ion Effects on the Interfacial Structure and Foam Properties of Polystyrene Sulfonate Solutions — •Felix Schulze-Zachau and Björn Braunschweig — Institut für Physikalische Chemie, Westfälische Wilhelms-Universität Münster, D-48149 Münster, Germany
Poly(sodium 4-styrenesulfonate) (NaPSS, 70 kDa) modified air/water interfaces were investigated with tensiometry, ellipsometry and vibrational SFG spectroscopy. Specific ion effects of K+, Ca2+ and Nd3+ on the interfacial structure and adsorption properties of 20 mM NaPSS were studied. For a better understanding of the behavior in the bulk phase, turbidity measurements were performed. In order to relate the molecular structure of NaPSS in the bulk and at the interface to macroscopic foam properties, foams of these mixtures were analyzed with respect to their stability and structure. SFG spectra reveal charge screening with increasing ionic strength which is more effective for higher charged ions and linked with high foam stability. For Ca2+ ions, a change in the intensity ratio of CH2/CH3 vibrational bands can be related to a change in molecular structure at low salt concentrations. Structural changes in the foams can be linked to this change of molecular structure as we observe a bimodal bubble size distribution which is connected with poor foam stability. With increasing ionic strength, a decrease in surface tension and an increase of adsorbate thickness as well as foam stability is observed. The reason for that is charge screening and formation of aggregates which stabilize the foam bubbles and give rise to small mean bubble sizes.