Polyelectrolyte/surfactant (P/S) mixtures find many applications but are static in nature and cannot be reversibly reconfigured through the application of external stimuli. Using a new type of photoswitchable surfactants, we use light to trigger property changes in mixtures of an anionic polyelectrolyte with a cationic photoswitch such as electrophoretic mobilities, particle size, as well as their interfacial structure and their ability to stabilize aqueous foam. For that, we show that prevailing hydrophobic intermolecular interactions can be remotely controlled between poly(sodium styrene sulfonate) (PSS) and arylazopyrazole tetraethylammonium bromide (AAP-TB). Shifting the chemical potential for P/S binding with E/Z photoisomerization of the surfactants can reversibly disintegrate even large aggregates (>4 μm) and is accompanied by a substantial change in the net charging state of PSS/AAP-TB complexes, e.g., from negative to positive excess charges upon light irradiation. In addition to the drastic changes in the bulk solution, also at air−water interfaces, the interfacial stoichiometry and structure change drastically on the molecular level with E/Z photoisomerization, which can also drive the stability of aqueous foam on a macroscopic level.

H-bond donor catalysts able to modulate the reactivity of ionic substrates for asymmetric reactions have gained great attention in the past years, leadingt ot he development of cooperative multidentate H-bonding supramolecular structures. However,t here is still al ack of understanding of the forces driving the ion recognition and catalytic performance of these systems. Herein, insight into the cooperativity nature, anion binding strength, and folding mechanism of am odel chiral triazole catalysti sp resented. Our combinede xperimentala nd computational study revealedthat multi-interaction catalysts exhibiting weak binding energies (% 3-4 kcal mol À1)c an effectively recognize ionic substrates and induce chirality,w hile strong dependencies on the temperature and solventw ere quantified. These results are key for the future design of catalystsw ith optimal anion bindings trength and catalytica ctivity in target reactions.

Triazole hosts allow cooperative binding of anions via hydrogen bonds, which makes them versatile systems for application in anion binding catalysis to be performed in organic solvents. The anion binding behavior of a tetratriazole host is systematically studied by employing a variety of salts, including chloride, acetate, and benzoate, as well as different cations. Classical nuclear magnetic resonance ( 1 H NMR) titrations demonstrate a large influence of cation structures on the anion binding constant, which is attributed to poor dissociation of most salts in organic solvents and corrupts the results of classical titration techniques. We propose an approach employing electrophoretic NMR (eNMR), yielding drift velocities of each species in an electric field and thus allowing a distinction between charged and uncharged species. After the determination of the dissociation constants K D for the salts, electrophoretic mobilities are measured for all species in the host-salt system and are analyzed in a model which treats anion binding as a consecutive reaction to salt dissociation, yielding a corrected anion binding constant K A . Interestingly, dependence of K A on salt concentration occurs, which is attributed to cation aggregation with the anion-host complex. Finally, by the extrapolation to zero salt concentration, the true anionhost binding constant is obtained. Thus, the approach by eNMR allows a fully quantitative analysis of two factors that might impair classical anion binding studies, namely, an incomplete salt dissociation as well as the occurrence of larger aggregate species.