When Bulk Matters: Disentanglement of the Role of Polyelectrolyte/Surfactant Complexes at Surfaces and in the Bulk of Foam Films

Abstract

Foam films display exciting systems as on one hand they dictate the performance of macroscopic foams and on the other hand they allow studies of surface forces. With regard to surface forces, we attempt to disentangle the effect of the foam film surfaces and the foam film bulk. For that, we study the influence of salt (LiBr) on foam films formed by mixtures of oppositely charged polyelectrolyte and surfactant: anionic monosulfonated polyphenylene sulfone (sPSO 2 -220) and cationic tetradecyltrimethylammonium bromide (C 14 TAB). Adding a small amount of salt (≤10 −3 M) decreases the foam film stability due to a weakened electrostatic net repulsion. In contrast, a large amount of salt (10 −2 M) unexpectedly increases the foam film stability. Disjoining pressure isotherms reveal that the increased stability is due to an additional steric stabilization, which is attributed to sPSO 2 -220/C 14 TAB complexes in the film bulk. These bulk complexes also contribute to the measured apparent surface potential between the two air/water interfaces. We find, for the first time, the formation of Newton black films for mixtures of anionic polyelectrolytes and cationic surfactants.

Photoresponsive arylazopyrazole surfactant/PDADMAC mixtures: reversible control of bulk and interfacial properties

“…Foams of P/S aggregates are mainly stabilized through electrostatic disjoining forces 41 or steric repulsion 8,9 as well as due to Pickering effects with larger particles. 13 When the surfactants are in the E state the disjoining pressure between gas bubbles is sufficiently high but is reduced drastically for the Z isomer where surfactant desorption from the interface (Fig.…”

“…[4][5][6][7] Owing to their widespread use in applications, the properties of P/S mixtures with classical surfactants like dodecylsulfate or alkylammonium in bulk solutions and at interfaces are studied extensively to the present day. [5][6][7][8][9][10][11][12] Using different P/S mixing ratios allows one to tailor soft matter properties such as the size of the P/S aggregates that form after mixing or the stability of aqueous foams.…”

Photoresponsive Arylazopyrazole Surfactant/PDADMAC Mixtures: Reversible Control of Bulk and Interfacial Properties

“…[4][5][6][7] Owing to their widespread use in applications, the properties of P/S mixtures with classical surfactants like dodecylsulfate or alkylammonium in bulk solutions and at interfaces are studied extensively to the present day. [5][6][7][8][9][10][11][12] Using different P/S mixing ratios allows one to tailor soft matter properties such as the size of the P/S aggregates that form after mixing or the stability of aqueous foam. However, these properties are notoriously difficult to change after P/S mixtures have been prepared, where only drastic changes in chemical composition e.g., pH values, or in the ionic strengths are useful triggers.…”

Developing Safe Organohydrogel Sunscreens Using Polyelectrolyte–Betaine Surfactant Complexes

“…On the other hand, polyelectrolyte/surfactant complexes are well-known for forming interfacial networks at gas/liquid and liquid/liquid interfaces through physical cross-linking. , These complexes are formed by the electrostatic interaction between oppositely charged polyelectrolytes and surfactants, resulting in the formation of a stable network at the interface. The main function of surfactants in this context is to increase the local concentration of hydrophobic cargo by forming self-assemblies that can encapsulate the cargo. , This is achieved through hydrophobic interactions between the surfactant molecules and the hydrophobic cargo.…”