Towards a better knowledge of U(VI) speciation in weakly alkaline solution through an in-depth study of U(VI) intrinsic colloids.

The formation of U(VI) intrinsic colloids has a non-negligible impact on the dissemination of actinides in the environment. It is therefore essential to better identify their nature, formation conditions, and stability domains. These specific points are especially important since the behavior of these elements in environment is generally estimated by geochemical transport modeling.

Rabies Virus Phosphoprotein Exhibits Thermoresponsive Phase Separation with a Lower Critical Solution Temperature.

Rabies virus (RABV) generates membrane-less liquid organelles (Negri bodies) in the cytoplasm of its host cell, where genome transcription and replication and nucleocapsid assembly take place, but the mechanisms of their assembly and maturation remain to be explained. An essential component of the viral RNA synthesizing machine, the phosphoprotein (P), acts as a scaffold protein for the assembly of these condensates. This intrinsically disordered protein forms star-shaped dimers with N-terminal negatively charged flexible arms and C-terminal globular domains exhibiting a large dipole moment.

Supramolecular Architectures of Dendritic Polymers Provide Irreversible Inhibitor to Block Viral Infection.

In Nature, most known objects can perform their functions only when in supramolecular self-assembled from, e.g. protein complexes and cell membranes.

Insertion of anionic synthetic clay in lamellar surfactant phases.

We describe the different mixed colloidal solutions that can be obtained when mixing equivalent quantities of a synthetic anionic clay to surfactants forming lamellar phases in the absence of added salt. The important quantity driving toward insertion or depletion is the osmotic pressure, of the lamellar phase and of the clay alone. Competition for water is the main driving force toward dispersion, inclusion or exclusion (phase separation).

Ion effects on co-existing pseudo-phases in aqueous surfactant solutions: cryo-TEM, rheometry, and quantification.

Hypothesis: Specific alkaline cation effects control the area per headgroup of alkylester sulphates, which modifies the spontaneous packing of the surfactants. The resulting effective packing minimizes the total bending energy frustration and results in a Boltzmann distribution of coexisting pseudo-phases. These pseudo-phases constitute of micelles and other structures of complex morphology: cylindrical sections, end-caps, branching points, and bilayers, all in dynamic equilibrium.

A dilute nematic gel produced by intramicellar segregation of two polyoxyethylene alkyl ether carboxylic acids.

Motivation: Surfactants like CECHCOOH have such bulky headgroups that they cannot show the common sphere-to-cylinder transition, while surfactants like CECHCOOH are mimicking lipids and form only bilayers. Mixing these two types of surfactants allows one to investigate the competition between intramicellar segregation leading to disc-like bicelles and the temperature dependent curvature constraints imposed by the mismatch between heads and tails.

Experiments: We establish phase diagrams as a function of temperature, surfactant mole ratio, and active matter content.

Structure of microemulsions in the continuous phase channel.

We have studied the microemulsion and lamellar phases of two of the most commonly described systems based on nonionic CE and ionic AOT surfactants. We show that CE is best described by the symmetric disordered open connected lamellar model (DOC-lamellar), contrary to the more commonly employed standard flexible model. In the case of AOT, the bicontinuous microemulsion structure is best described by the standard flexible model at high temperatures.

Two Types of Liquid Phase Separation Induced by Soft Centrifugation in Aqueous Ethyl Acetate Using Ethanol as Cosolvent.

Water/ethyl acetate/ethanol is widely used as a "green" extractant system. We show that 2 different types of phase separation can be induced upon centrifugation in this ternary system using ethanol as a cosolvent of water and ethyl acetate: centrifuge-induced criticality and centrifuge-induced emulsification. The expected composition profiles of samples after centrifugation can be represented by bent lines in a ternary phase diagram when gravitational energy is added to the free energy of mixing.

How colloid nature drives the interactions between actinide and carboxylic surfactant in sol: Towards a mesostructured nanoporous actinide oxide material.

Hypothesis: The key to prepare a mesostructured porous material by a soft-template route coupled to a colloidal sol-gel process is to control the surfactant-colloid interface. In the case of tetravalent actinide ions, their high reactivity in aqueous media always leads to uncontrolled and irreversible condensation. The addition of a complexing agent to the sol may moderate these reactions and enhances the interaction between the colloids and the surfactant to in fine prepare a mesostructured nanoporous actinide oxide material.

Swollen cubic phases with reduced hardness solubilizing a model fragrance oil as a co-surfactant.

Swollen cubic lyotropic ternary phases with Pn3m symmetry and reduced hardness were obtained from a specific binary mixture of cubic phase-forming (phytantriol) and lamellar phase-forming (decaglycerol monooleate) compounds. The microstructures were determined by using a small-angle x-ray scattering technique. The softness and temperature-induced phase transitions were investigated by means of rheology.

Facile Preparation of Macro-Microporous Thorium Oxide via a Colloidal Sol-Gel Route toward Safe MOX Fuel Fabrication.

The identification of new colloidal sol-gel routes for the preparation of actinide oxides, which have a homogeneous and accessible porosity that can easily be impregnated by any concentrated actinide solution, opens new perspectives for the preparation of homogeneous nuclear fuel for minor actinide transmutation. This homogeneity allows us to avoid "hot spot" formation due to the local accumulation of more fissile elements. Here, we report the preparation of macro-microporous ThO materials by a colloidal sol-gel route.

The effect of ethanol on fibrillar hydrogels formed by glycyrrhizic acid monoammonium salt.

Motivation: The monoammonium salt of glycyrrhizic acid (AGA) is known to form fibrillar hydrogels and few studies regarding self-assembly of AGA have been published. Yet, the understanding of the fibrillar microstructures and the gelation remains vague. Thus, we attempt to achieve a deeper understanding of the microstructures and the gelation process of binary solutions of AGA in water.

Specific analysis of highly absorbing nanoporous powder by small-angle X-ray scattering.

The characterization of nanoporous powders of highly absorbing compounds by small-angle X-ray scattering (SAXS) involves overcoming several difficulties before quantitative information related to the porous texture, such as the specific surface and the porous volume, can be derived. In this article, first, the contribution of the grain facet reflectivity and scattering from the bulk of a grain with the density of ThO, a highly absorbing material, were calculated. Microporous ThO powder having micrometric grain size was characterized, in which the scattering signal is predominant.

Short-chain branched sulfosuccinate as a missing link between surfactants and hydrotropes.

Surfactants aggregate in water into micelles, and these micelles incorporate organic substances to solubilize them. Hydrotropes are compounds that increase the solubility of hydrophobic substances in water without this form of aggregation. Decreasing the chain length of the classical surfactant Aerosol OT (AOT) from C8 to C5 results in a molecule with intermediate properties.

Cloud point, auto-coacervation, and nematic ordering of micelles formed by ethylene oxide containing carboxylate surfactants.

Hypothesis: In a recent paper, we determined the phase behavior of an aqueous solution of octyl ether octaethylene oxide carboxylic acid ([H][C8E8c], Akypo™ LF2) and with partial replacement of H by Na and Ca. It was found that even the neat surfactants are liquid at room temperature and that they form only direct micelles for any aqueous content and over large temperature ranges. The aim of the present work was to find an explanation for the clouding in these systems as well as for the coacervation observed at very low surfactant content.

Theory of Ternary Fluids under Centrifugal Fields.

In this work, we developed a general theoretical description of ternary solutions of small molecules under a centrifugal field, from which we obtained the centrifugation map (CMap) as a general tool to understand observations or to predict composition profiles in centrifugal fields of arbitrary strength. The theoretical formalism is based on the classical density functional theory with established models for liquid mixtures. Thermodynamics also yields a general criterion for apparent aggregation.

Molecular Forces in Liquid-Liquid Extraction.

The phase transfer of ions is driven by gradients of chemical potentials rather than concentrations alone (i.e., by both the molecular forces and entropy).

Using Microemulsions: Formulation Based on Knowledge of Their Mesostructure.

Microemulsions, as thermodynamically stable mixtures of oil, water, and surfactant, are known and have been studied for more than 70 years. However, even today there are still quite a number of unclear aspects, and more recent research work has modified and extended our picture. This review gives a short overview of how the understanding of microemulsions has developed, the current view on their properties and structural features, and in particular, how they are related to applications.

Spontaneous Ouzo Emulsions Coexist with Pre-Ouzo Ultraflexible Microemulsions.

Even in the absence of surfactants, polymers, or particles, spontaneous emulsions produced by dilution with water can be stable over days. This "Ouzo effect" used by the industry is obtained by rapid dilution from an identified "pre-Ouzo" domain of composition where weak aggregates are present: nanometer-sized clusters covered by a surface layer enriched in a hydrotrope such as ethanol. In these systems, Ostwald ripening is not an effective destabilizing mechanism.

Phase diagrams and microstructures of aqueous short alkyl chain polyethylene glycol ether carboxylate and carboxylic acid triblock surfactant solutions.

Hypothesis: The surfactant CEOCHCOOH (Akypo LF2) and its salts have a small hydrophobic and a significantly longer hydrophilic part. As a consequence, there must be a significant steric constraint, once these surfactant molecules form micelles. In addition, the partially charged headgroups should bring some additional fine-tuning via electrostatic interactions to this "essentially non-ionic" surfactant.

How Adsorption of Pheromones on Aerosols Controls Their Transport.

We propose a general transport theory for pheromone molecules in an atmosphere containing aerosols. Many pheromones are hydrophobic molecules containing polar groups. They are low volatile and have some properties similar to those of hydrotropes.

A microfluidic study of synergic liquid-liquid extraction of rare earth elements.

A microfluidic technique is coupled with X-ray fluorescence in order to investigate the origin of the so-called synergy effect observed in liquid-liquid extraction of rare earth elements (REEs) when special combinations of two extractants - one solvating and one ionic - are used. The setup enables kinetic studies by varying the two phases' contact time. The results obtained are compared with those obtained using a standard batch extraction method at identical contact time.

Synergistic Solvent Extraction Is Driven by Entropy.

In solvent extraction, the self-assembly of amphiphilic molecules into an organized structure is the phenomenon responsible for the transfer of the metal ion from the aqueous phase to the organic solvent. Despite their significance for chemical engineering and separation science, the forces driving the solute transfer are not fully understood. Instead of assuming the simple complexation reaction with predefined stoichiometry, we model synergistic extraction systems by a colloidal approach that explicitly takes into account the self-assembly resulting from the amphiphilic nature of the extractants.