Molten fatty acid based microemulsions †

International audiencea We show that ternary mixtures of water (polar phase), myristic acid (MA, apolar phase) and cetyltrimethyl-ammonium bromide (CTAB, cationic surfactant) studied above the melting point of myristic acid allow the preparation of microemulsions without adding a salt or a co-surfactant. The combination of SANS, SAXS/ WAXS, DSC, and phase diagram determination allows a complete characterization of the structures and interactions between components in the molten fatty acid based microemulsions. For the different structures characterized (microemulsion, lamellar or hexagonal phases), a similar thermal behaviour is observed for all ternary MA/CTAB/water monophasic samples and for binary MA/CTAB mixtures without water: crystalline myristic acid melts at 52 1C, and a thermal transition at 70 1C is assigned to the breaking of hydrogen bounds inside the mixed myristic acid/CTAB complex (being the surfactant film in the ternary system). Water determines the film curvature, hence the structures observed at high temperature, but does not influence the thermal behaviour of the ternary system. Myristic acid is partitioned in two ''species'' that behave independently: pure myristic acid and myristic acid associated with CTAB to form an equimolar complex that plays the role of the surfactant film. We therefore show that myristic acid plays the role of a solvent (oil) and a co-surfactant allowing the fine tuning of the structure of oil and water mixtures. This solvosurfactant behaviour of long chain fatty acid opens the way for new formulations with a complex structure without the addition of any extra compound

La mer, miroir de la légitimité du califat nasride. A propos du Khatrat al-tayf d’Ibn al-Khatîb (1347)

International audienc

Design of Double Stimuli-Responsive Polyelectrolyte Microcontainers for Protein Soft Encapsulation

International audienc

Polymer Microcapsules with Carbohydrate-Sensitive Properties

International audienc

Synthèse asymétrique phosphorés (alpha)-aminés et expression de la reconnaissance chirale dans leurs modes d'agrégation

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Surfactin Self-Assembles into Direct and Reverse Aggregates in Equilibrium and Performs Selective Metal Cation Extraction

International audienc

Ion-specific weak adsorption of salts and water/octanol transfer free energy of a model amphiphilic hexapeptide

International audienceAn amphiphilic hexapeptide has been used as a model to quantify how specific ion effects induced by addition of four salts tune the hydrophilic/hydrophobic balance and induce temperature-dependant coacervate formation from aqueous solution. The hexapeptide chosen is present as a dimer with low transfer energy from water to octanol. Taking sodium chloride as the reference state in the Hofmeister scale, we identify water activity effects and therefore measure the free energy of transfer from water to octanol and separately the free energy associated to the adsorption of chaotropic ions or the desorption of kosmotropic ions for the same amphiphilic peptide. These effects have the same order of magnitude: therefore, both energies of solvation as well as transfer into octanol strongly depend on the nature of the electrolytes used to formulate any buffer. Model peptides could be used on separation processes based on criteria linked to “Hofmeister” but different from volume and valency

Effects of Alkaline Cations on Self-assembly of Cetylpyridinium Surfactants

International audienc

How Do Anions Affect Self-Assembly and Solubility of Cetylpyridinium Surfactants in Water

International audienceWe report the specific effects of a series of anions (chloride, nitrate, and oxalate) on the solubility and self-assembly of cationic cetylpyridinium surfactants in water. The anion influence on micellization was evidenced by tensiometry and determination of Krafft temperatures. Anions strongly affect these parameters, depending on their position in the lyotropic series as well as on their “bridging” character. Scattering techniques (light, X-rays, and neutrons) were used to characterize the structures of micelles, and by solving a lateral equation of state approach, we show that chaotropic anions can be considered as adsorbed on the pyridinium head groups, inducing a decrease of the surface polarity and a Krafft temperature shift. Mixing different counteranions in various ratios led to a competition with a preferential adsorption at the micellar surface