A structural study of perfluorosulfonated ionomer (PFSI) solutions in polar solvents such as alcohols, amides, and water using both small-angle X-ray and neutron scattering is presented. Contrast variation methods have shown that the ionomer molecule particles form dense particles of constant scattering length. The study of dilute solutions allows one to evidence the rodlike structure of PFSI solutions. The radius of the cylindrical particles is determined from both the shape and the intensities of the scattering curves. These results are confirmed by the analysis of the asymptotic behavior at large angles of the scattering curves. Typical values for the radii are found to be around 20 Å. The diameter of the rod is shown to be related to the polymer−solvent interfacial energy, whereas the dielectric constant of the solvent acts only on the local order. Mixtures of solvents have been used to check the evolution of the structure with the solvents. The effect of the counterion is also studied. The effect of added salt on the small-angle scattering spectra can be interpreted as due to a decrease of the local order through the disappearance of the interference term and the shape of the particles is not modified.

Résumé. 2014 Nous examinons les résultats d'expérience de diffusion de neutrons aux petits angles (10-2 q 2 x 10-1 Å-1) par des solutions de sulfonate de polystyrène dans l'eau pour des concentrations supérieures à 0,5 x 10-2 g. cm-3.Avec de l'eau ultra pure, l'absence de diffusion centrale et la présence d'un maximum pour les plus grandes valeurs de q caractérisent la fonction de diffusion S(q). Les deux effets étudiés, variation de la concentration en polyions et addition de sel, conduisent à des résultats différents : la position du maximum varie avec la concentration de polyions alors qu'avec l'addition de sel, on note l'apparition de diffusion centrale et disparition du maximum.Abstract. 2014 Solutions of polyelectrolyte are studied by small angle neutron scattering for c > 0.5 x 10-2 g. cm -3.The function S(q) is characterized by a small value of S'(q ~ 0) and one broad maximum for higher q's

The adsorption and complexation of polystyrene sulfonate (a highly charged anionic polyelectrolyte) and dodecyltrimethylammonium bromide (a cationic surfactant) at the air-water interface can lead to interfacial gels that strongly influence foam-film drainage and stability. The formation and characteristics of these gels have been studied by combining surface tension, ellipsometry, and foam-film drainage experiments. Simultaneously, the solution electromotive force is measured and used to track the polymer-surfactant interactions in the bulk solution. We find that surface gelation occurs above the critical aggregation concentration in solution but before bulk precipitation of the polymer-surfactant complexes. Furthermore, we reveal that strong readsorption of polymer-surfactant complexes occurs during the resolubilization of the precipitated complexes at high surfactant concentrations (i.e., >>critical micelle concentration). Seemingly overlooked in the past, this readsorption significantly influences the surface rheological properties and foam-film drainage of these systems.

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