Insights into Extended Structures and Their Driving Force: Influence of Salt on Polyelectrolyte/Surfactant Mixtures at the Air/Water Interface.

This paper addresses the effect of polyelectrolyte stiffness on the surface structure of polyelectrolyte (P)/surfactant (S) mixtures. Therefore, two different anionic Ps with different intrinsic persistence length are studied while varying the salt concentration (0-10 M). Either monosulfonated polyphenylene sulfone (sPSO-220, ∼20 nm) or sodium poly(styrenesulfonate) (PSS, ∼1 nm) is mixed with the cationic surfactant tetradecyltrimethylammonium bromide (CTAB) well below its critical micelle concentration and studied with tensiometry and neutron reflectivity experiments.

New structural approach to rationalize the foam film stability of oppositely charged polyelectrolyte/surfactant mixtures.

A novel structural framework is presented to rationalize the foam film stability of polyelectrolyte/surfactant mixtures using neutron reflectivity data. Provision of electrostatic or steric stabilization in thin foam films is related to the spatial distributions of molecules interacting from opposing air/water interfaces. The advance is discussed in the context of many studies on mixed systems over two decades that focused on macroscopic properties such as the surface tension, elasticity, potential and composition, but for which no robust correlations have been established.

Polymers and surfactants at fluid interfaces studied with specular neutron reflectometry.

This review addresses the advances made with specular neutron reflectometry in studies of aqueous mixtures of polymers and surfactants at fluid interfaces during the last decade (or so). The increase in neutron flux due to improvements in instrumentation has led to routine measurements at the air/water interface that are faster and involve samples with lower isotopic contrast than in previous experiments. One can now resolve the surface excess of a single deuterated component on the second time scale and the composition of a mixture on the minute time scale, and information about adsorption processes and dynamic rheology can also be accessed.

Surface adsorption of sulfonated poly(phenylene sulfone)/C14TAB mixtures and its correlation with foam film stability.

Polyelectrolyte/surfactant mixtures of rigid monosulfonated poly(phenylene sulfone) (sPSO2-220) and tetradecyl trimethylammonium bromide (C14TAB) were investigated by surface tension, surface elasticity and foam film stability measurements. The results were compared to former measurements of polyelectrolyte/surfactant mixtures containing more flexible polyelectrolytes (PAMPS or PSS and C14TAB). For all polyelectrolyte/surfactant mixtures an increased surface adsorption in comparison to the pure surfactant was detected.

Two-Dimensional Aggregation and Semidilute Ordering in Cellulose Nanocrystals.

The structural properties and aggregation behavior of carboxymethylated cellulose nanocrystals (CNC-COOH) were analyzed with small angle neutron scattering (SANS), transmission electron microscopy (TEM), atomic force microscopy (AFM), and dynamic light scattering (DLS) and compared to sulfuric acid hydrolyzed cellulose nanocrystals (CNC-SO3H). The CNC-COOH system, prepared from single carboxymethylated cellulose nanofibrils, was shown to laterally aggregate into 2D-stacks that were stable both in bulk solution and when adsorbed to surfaces. CNC-SO3H also showed a 2D aggregate structure with similar cross sectional dimensions (a width to height ratio of 8) as CNC-COOH, but a factor of 2 shorter length.

Surface Adsorption of Oppositely Charged SDS:C(12)TAB Mixtures and the Relation to Foam Film Formation and Stability.

The complexation, surface adsorption, and foam film stabiliztation of the oppositely charged surfactants, sodium dodecyl sulfate (SDS) and dodecyl trimethylammonium bromide (C12TAB), is analyzed. The SDS:C12TAB mixing ratio is systematically varied to investigate whether the adsorption of equimolar or irregular catanionic surfactant complexes, and thus a variation in surface charge (i.e.