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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 53: Charged Soft Matter, Polyelectrolytes and Ionic Liquid

CPP 53.5: Vortrag

Donnerstag, 30. März 2023, 16:30–16:45, ZEU 255

Photoisomerization of Arylazopyrazole Surfactants Drives Property Changes of Polyelectrolyte/Surfactant Mixtures — •Michael Hardt and Björn Braunschweig — University Münster, Center for Soft Nanoscience, 48149 Münster, Germany

Polyelectrolyte/surfactant (P/S) mixtures are in most cases static in nature, which renders them invariable for property changes unless massive changes in pH or ionic strength are applied. We have shown that mixtures of cationic photo-responsive arylazopyrazole (AAP) surfactants with NaPSS exhibit substantial changes in particle size and electrophoretic mobility [1] that can be easily triggered by light irradiation.
Here, we present new information on PDADMAC polyelectrolyte mixtures with three anionic AAP surfactants that have H, butyl and octyl terminal groups. The E and Z configurations of the AAP photoswitches show substantially different hydrophobic interactions that drastically alter their binding affinity to the PDADMAC. Measurements of the electrophoretic mobility clearly indicate that the E/Z photoisomerization of AAP surfactants causes a charge reversal of the P/S aggregates, while for the H-AAP also larger P/S aggregates in the bulk solution can be dissolved by UV irradiation and formed again with green light. Vibrational sum-frequency generation (SFG) spectroscopy reveals that similar to the changes in the bulk, the charging state at the air-water interface can be reversibly tuned by the light conditions. This has interesting consequences for soft matter materials such as foams [1] and emulsions.
[1] Schnurbus et al., ACS Appl. Mater. Int. 2022, 14, 4656-4667.