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Low charge density nanometric ions were recently shown to bind strongly to neutral hydrated matter in aqueous solution. This phenomenon, called the (super-)chaotropic effect, arises from the partial dehydration of both the nano-ion and the solute, leading to a significant gain in enthalpy. Here, we investigate the chaotropic effect of the polyoxometalate α-PW12O403− on the triblock copolymer P84: (EO)19(PO)43(EO)19 with (EO)19 the polyethoxylated and (PO)43 the polypropoxylated chains. The combination of phase diagrams, spectroscopic (nuclear magnetic resonance) and scattering (small angle neutron/X-ray scattering) techniques revealed that: (i) below the micellization temperature of P84, PW12O403− exclusively binds to the propylene oxide moiety of P84 unimers; and (ii) above the micellization temperature, PW12O403− mostly adsorbs on the ethylene oxide micellar corona. The preferential binding of the PW12O403− to the PPO chain over the PEO chains suggests that the binding is driven by the chaotropic effect and is reinforced by the hydrophobic effect. At higher temperatures, copolymer micellization leads to the displacement of PW12O403− from the PPO chain to the PEO chains. This study deepens our understanding of the subtle interplay between the chaotropic and hydrophobic effects in complex salt-organic matter solutions. [ABSTRACT FROM AUTHOR]

Recently, nanometric ions were shown to adsorb to hydrated neutral surfaces and to bind to the cavities of macrocyclic molecules with an unexpectedly strong affinity arising from a solvent‐mediated effect named superchaotropicity. We show here that nano‐ions at low concentrations (μm range), similarly to anionic surfactants, induce the spontaneous transformation of a swollen lyotropic lamellar phase of non‐ionic surfactant into a vesicle phase. This transition occurs when the neutral lamellae acquire charges, either by adsorption of the nano‐ions onto, or by anchoring of the ionic surfactant into the lamellae. In contrast to ionic surfactants, nano‐ions strongly dehydrate the neutral surfactant assemblies. As a conclusion, these purely inorganic nanometric ions act as alternatives to the widely used organic ionic surfactants. [ABSTRACT FROM AUTHOR]

We propose a simple experimental procedure based on the cloud point measurement of a non-ionic surfactant as a tool for (i) estimating the super-chaotropic behaviour of polyoxometalates (POMs) and for (ii) establishing a classification of POMs according to their affinity towards polar surfaces. [ABSTRACT FROM AUTHOR]

[3,3'-Co(1,2-C2B9H11)2]-, [1]-, and its chloroderivatives have been described as displaying surfactant/ aggregation properties. We have studied their behaviour as electrolytes in the water electrolysis process. The electrolysis experiments support the surfactant behaviour of these compounds. These conclusions have been drawn on the grounds of the intensity/voltage (I/V) curves of water splitting into H2 and O2 of aqueous solutions in which the electrolytes have been tested at the same concentration. The I/V curves have permitted us to map and group the different electrolytes studied in this work. Three differentiated zones have been observed: one for true electrolytes, NO3- and ClO4-; a second one for intermediate electrolytes, BF4- and p-toluenesulfonate (PTS); and a third having the surfactant dodecylbenzenesulfonate (DBS), [1]- and its chloroderivatives. The incorporation into the study of the chloroderivatives of [1]- has allowed us to correlate molecular structure features with aqueous performance. The studied chloroderivatives perform better as electrolytes in accordance with the descending order of available B-H groups. This comes from the higher capacity to generate B-H...H-Cc dihydrogen bonds in the non- or less-halogenated molecules, considered one of the main reasons for the generation of the aggregates. In order to generate B-H...H-Cc dihydrogen bonds the H-Cc from the carborane cluster is needed. [B12H12]2- was chosen to prove the hypothesis as it has B-H units but lacks H-Cc units. Consequently, it should not produce self-assembling motifs, as is the case. [B12H12]2- has an aqueous behaviour similar to SO42-. [ABSTRACT FROM AUTHOR]

Abstract: For colloidal solutions containing any type of surfactant inducing the formation of locally flat interfaces, we show here that two equations of state are required to understand phase behaviour and stability: the perpendicular and the lateral equations of state. This applies to lamellar phases, locally lamellar connected or sponge phases, uni- and multilamellar vesicle phases formed by detergents, lipids, extractants and theta-shaped molecules in all solutions showing optical anisotropy. [Copyright &y& Elsevier]

Steadystate foams made of a pH sensitive surfactant, nonaoxyethyleneoleylether carboxylic acid, with ion complexing properties was studiedusing small angle neutron scattering (SANS). The effect of pH variationand salt addition on the foam film thickness was investigated anddiscussed in terms of the influent parameters stabilizing the foamsuch as surface properties and electrostatic effects determined bytensiometry and zeta potential measurements. The decrease in the filmthickness by adding mono (Na+) and divalent (Ca2+) salts is classically explained by screening of the double layerin foam films (transverse interactions). On the contrary, additionof acid or complexing ion (Nd3+) results in an increasein the film thickness and can be analyzed in terms of cohesive forcesbetween surfactants at the liquid/gas interface (lateral interactions).pH and specific salt effects revealed that foams produced by nonaoxyethyleneoleylether carboxylic acid are of interest in the potential use ofthis surfactant in ion separation process. [ABSTRACT FROM AUTHOR]

Abstract: The effect of adding salts to micelles made of a sugar based surfactant, n-octyl-beta-glucoside, has been investigated using small angle X-ray scattering (SAXS) and dynamic light scattering (DLS) techniques. It was shown that adding salts leads to change the outer shell hydration of the micelles i.e. where the glucose moieties are situated. No ion adsorption at the micelle surface was detected. Three regimes have been determined as a function of the ionic strength (IS): (i) at low IS (<1M), no significant effect on the hydration of the surfactant sugar moieties was detected while at (ii) intermediate IS (1–1.8M) a salting-in effect was observed, i.e. a strengthening of the hydration of the glucose polar heads at the micelle surface, and at (ii) higher IS a strong salting-out effect is detectable i.e. strong dehydration of the polar head inducing an increase in the micelle size. It is noteworthy to remark that such a transition from a salting-in to a salting-out effect is observed with classical polyethoxylated surfactants (CiEj) when measuring the cloud point as a function of a salting-in electrolyte concentration i.e. the cloud point shows an increase and then a decrease by addition of the electrolyte. [Copyright &y& Elsevier]

In the present contribution, we investigated the influence of the structuring of surfactant-free microemulsions (SFME) (water/1-propanol/limonene and water/ tert -butanol/limonene) on the enzyme activity of horseradish peroxidase (HRP). To this purpose, the oxidation of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) with hydrogen peroxide was chosen as a model reaction. Enzymatic activities in SFMEs of varying compositions were investigated by UV–Vis spectroscopy and compared to the enzyme activity in pure buffer solution. Dynamic light, small-angle-X-ray scattering and conductivity measurements were performed in order to obtain structural information on the used SFMEs. Findings presented in this study revealed that the ability of short-chain alcohols to form mesostructures (aqueous aggregates in oil) has a crucial effect on the enzyme activity in SFMEs. Mesoscale structuring with 1-propanol (NPA) was found to be more pronounced than for the more hydrophobic tert -butanol (TBA). It was concluded that the most pronounced mesoscale-structured SFMEs lead to the highest enzymatic activities. [ABSTRACT FROM AUTHOR]

Unlike the self‐assembly of other surfactants, that of metallacarborane clusters, described as θ‐shaped amphiphiles, does not originate from the hydrophobic effect. In their Communication on page 12114 ff., P. Bauduin et al. show that specific interactions involving many intermolecular dihydrogen bonds, such as CHδ+⋅⋅⋅δ−HB, are the key to understanding the aggregation process in water. This peculiarity results in the formation of lyotropic lamellar phases with a unique monomolecular structure. [ABSTRACT FROM AUTHOR]

Self-aggregation of eight dimethyl-di-N-octylammonium salts ([DiC8]) has been investigated as a function of the nature of the counteranion. Tensiometry, conductimetry, and [DiC8]-selective electrode measurements highlighted three different behaviors and led to a rationalization of the aggregation process depending on the counteranion: “hydrophilic” anions (MoO42–, WO42–, SO42–, F–) give only unimers and micelles, whereas less hydrated anions form unimers, dimers, and either one micelle-like structure (NO3–, Br–) or two micelle-like structures (CH3SO3–, Cl–). Small-angle neutron and dynamic light scattering confirms the unusual behavior of [DiC8][Cl], which forms two types of aggregates: (i) disk or vesicles between 10 and 30 mM and (ii) ellipsoidal micelles above 30 mM. For [DiC8][MoO42–], the formation of ellipsoidal micelles is supported between 10 and 300 mM. Finally, shapes and sizes of the aggregates are confirmed by molecular dynamic experiments. [ABSTRACT FROM AUTHOR]

• The superchaotropic nature of the Krebbs anion, Mo 36 O 112 8−, is shown for the first time. • Polyoxometalates formed by varying pH/concentration do bind with non-ionic surfactants. • Ion separation is performed here for the first time by non-ionic surfactant foams. • Non-ionic surfactants affect the equilibria of formation of foam extractible polyoxometalates. • As a proof of concept, W and Mo were separated by using a polyethoxylated (non-ionic) surfactant. Ion flotation is a separation technology for recovering ions from dilute aqueous solutions. All ion flotation processes known so far make use of ionic foaming agents (surfactants) to selectively extract ions of opposite charge by electrostatic interactions. Recently, it was shown that nanometric-sized ions (nano-ions) with low charge density, such as certain polyoxometalates (POMs), strongly adsorb to neutral hydrated surfaces. In this study, we provide proof-of-concept for a method that we call "superchaotropic ion flotation," which uses non-ionic surfactant foams to selectively recover and separate superchaotropic POMs from other ions, including non-superchaotropic ions. Specifically, we investigated the extraction of isopolyoxomolybdates, formed by pH and concentration variation of molybdate aqueous solutions, using foams produced with a commercial polyethoxylated surfactant (BrijO10). The speciation of polyoxomolybdates was investigated by Raman spectroscopy and small angle X-ray scattering (SAXS). SAXS has also confirmed the superchaotropic behaviour of the polyoxomolybdates species via the characterization of their strong adsorption on surfactant micelles. The flotation recovering is high and maximal at pH 1, a pH for which Mo 36 O 112 8−, an anion with a low charge density, is the predominant molybdate species. It was found that the surfactant has a strong influence on the molybdate speciation. It was also demonstrated that molybdate may be separated from tungstate at pH 2 by superchaotropic ion flotation. In conclusion, we propose a novel ion separation method via non-ionic surfactant aqueous foams and we show that the superchaotropic effect makes it possible to foresee various applications in separation science. [ABSTRACT FROM AUTHOR]

Separation of metal cations of different charges, Na + , Li + , Ca 2+ , Sr 2+ , Cu 2+ , Nd 3+ and Eu 3+ was investigated through ion foam flotation using a pH sensitive surfactant, nonaoxyethylene oleyl ether carboxylic acid. We propose here a method to evaluate ion selectivity coefficients using mass and volume balances. This method yields selectivity coefficients in agreement with those obtained with the classical slope method. The ion selectivity obtained by the flotation experiments was found to correlate well with the apparent charge of the surfactant micelles (zeta potential values) in the presence of different salts and is therefore not influenced by the surface curvature. Consequently the ion specificity order has been established according to the surfactant–ion affinity at the air–water and micelle–water interfaces as Na + < Li + < Sr 2+ < Ca 2+ < Cu 2+ < Nd 3+ < Eu 3+ . It has been noticed that the selectivity coefficients between the different metal ions, obtained by ion flotation, differ from the ones predicted by using metal ion complexation constants of acetate, which is considered here as the non-surface active complexing part of the surfactant. This discrepancy was attributed to the surface complexation effects at the air–water interface in flotation experiments and at the micelle–water interface. For the separation of lithium and neodymium, a depletion phenomenon of lithium ions from the interface, hence from the foam, has been observed, i.e. once the flotation experiment was finished, the lithium concentration in the remaining foaming solution was indeed higher compared to the initial one. This phenomenon was explained by the strong adsorption of Nd 3+ that leads Li + to be repelled from the foam. [ABSTRACT FROM AUTHOR]

Because of their amphiphilic structure,surfactants adsorb at thewater–air interface with their hydrophobic tails pointing outof the water and their polar heads plunging into the liquid phase.Unlike classical surfactants, metallabisdicarbollides (MCs) do nothave a well-defined amphiphilic structure. They are nanometer-sizedinorganic anions with an ellipsoidal shape composed of two carboranesemicages sandwiching a metal ion. However, MCs have been shown toshare many properties with surfactants, such as self-assembly in water(formation of micelles and vesicles), formation of lamellar lyotropicphases, and surface activity. By combining second harmonic generationand surface tension measurement, we show here that cobaltabis(dicarbollide)anion {[(C2B9H11)2Co]−also named [COSAN]−} with H+as a counterion, the most representative metallacarborane,adsorbs vertically at the water surface with its long axis normalto the surface. This vertical molecular orientation facilitates theformation of intermolecular and nonconventional dihydrogen bonds suchas the B–Hδ−···δ+H–C bond that has recently been proven to beat the origin of the self-assembly of MCs in water. Therefore, itappears here that lateral dihydrogen bonds are also involved in thesurface activity of MCs. [ABSTRACT FROM AUTHOR]

Abstract: In this work, we report on the phase behavior of 1-ethyl-3-methyl-imidazolium-ethylsulfate ([emim][etSO4])/limonene/polyethylene glycol tert-octylphenyl ether (Triton X-114 or TX-114) microemulsions as a function of ionic liquid (IL) content and temperature. Phase diagrams, conductivity measurements, and small angle X-ray scattering (SAXS) experiments will be presented. A hydrophilic IL, instead of water is used with the goal to enlarge the temperature range on which stable microemulsions can be formed. Indeed, the system shows remarkably large temperature stability, in particular down to −35°C. We will emphasize on a comparison with a recently published work about microemulsions composed of [emim][etSO4], limonene, and Triton X-100 that to some extent are stable at temperatures well below the freezing point of water. The key parameter responsible for the difference in phase behavior, microstructure, and temperature stability is the average repeating number of ethylene oxide units in the surfactant head group, which is smaller for Triton X-114 compared to Triton X-100. Among the fundamental interest, how the amphiphilicity of the surfactant influences the phase diagram and phase behavior of IL-based microemulsions, the exchange of Triton X-100 by Triton X-114 results in one main advantage: along the experimental path the temperature where phase segregation occurs is significantly lowered leading to single phase microemulsions that exist at temperatures beneath 0°C. [Copyright &y& Elsevier]