Polyoxometalates (POMs) are nanometric metal-oxide anions with unique chemical and physical properties. During last decade, significant efforts have been made to give POMs surface activity and self-assembly properties that are essential for catalysis applications and for producing organic-inorganic hybrid materials. In this work, POMs based surfactants are produced spontaneously through non-covalent interactions in water by mixing non-ionic surfactants with POM. The most common POMs of tungstosilicate and tungstophosphate, have indeed an unexpected strong tendency to adsorb on polar and neutral interfaces. Micelles in water and water/air interfaces were investigated by SAXS and ion flotation showing the POM anions adsorbed at the micelle surface and on monolayers of non-ionic surfactants. This general property of POM provides a unique opportunity for deeper understanding of many medicinal effects of POMs, i.e. their antiviral and antitumor activities that involves their specific adsorption on biological surfaces.

In the last decadeo rganic-inorganic hybrid materials have becomeessential in materials science as they combine properties of both buildingb locks. Nowadays the main routes for their synthesis involve electrostatic coupling, covalent grafting, and/or solvente ffects. In this field, polyoxometalates (POMs) have emerged as interesting inorganic functional buildingb locks due to their outstanding properties. In the present work the well-known a-Keggin polyoxometalate, a-PW 12 O 40 3À (PW), is shown to form hybrid crystalline materials with industrial (neutral) polyethylene glycol oligomers (PEG) under mild conditions, that is, in aqueous medium and at room temperature. The formation of these materials originates from the spontaneous self-assembly of PW with EO x ,( EO = ethylene oxide)w ith at least four EO units (x > 4). The PW-PEG nanoassemblies, made of aP OM surrounded by about two PEG oligomers, are stabilized by electrostatic repulsions betweent he negatively charged PW anions.A ddition of NaCl, aimed at screening the inter-nanoassembly repulsions,i nduces aggregation and formationo f hybrid crystalline materials. Single-crystal analysiss howed ah igh selectivity of PW towards EO 5 -EO 6 oligomers from PEG200, which is made of am ixture of EO 3-8 .T herefore, ag eneral "soft" route to produce POM-organic composites is proposed here through the controlo fe lectrostatic repulsions between spontaneously formed nanoassemblies in water.H owever, this rational design of new POM hybrid (crystalline) materials with hydrophilic blocks, using such as imple mixing procedureo ft he components, requires ad eep understanding of the molecular interactions.

The micellar properties of gemini surfactant, tetramethylene-1,4-bis(dimethyltetradecylammonium bromide) (14-4-14) in binary aqueous mixtures of isopropanol (IP) and 1,4-dioxane (DO) were investigated by tensiometric, conductometric and microcalorimetric methods in the temperature range of 298 to 323 K. The values of both critical micelle concentration (cmc) and degree of dissociation increase with increasing temperature and concentration of cosolvent. The energetics of micellization was determined from the temperature dependence of critical micelle concentration values. The standard Gibbs free energy of micellization (ΔG) was found to be negative and the negative value decreases with both temperature and concentration of cosolvent. The Gibbs free energy of micellization (ΔG) is mainly controlled by tail transfer free energy. The enthalpy of micellization obtained from direct calorimetry, Gibbs-Helmholtz equation and van't Hoff methods are presented and compared. Entropic contribution is found to be larger than the enthalpy and for all the systems, an enthalpy-entropy compensation phenomenon was obtained. Some interfacial parameters, e.g., Gibbs surface excess (Γmax), minimum area per surfactant molecule (Amin), surface pressure (Πcmc) were been calculated. The fluorimetric technique was used to understand the microenvironment of the solution under the influence of cosolvent. The micellar aggregation number of 14-4-14 in a binary mixed solvent was also determined from fluorimetry using pyrene as a probe. Two fluorophores, fluorescein and curcumin delivered the information of the peripheral region of the micellar interface and palisade region. The self-diffusion coefficients of the micellar media were evaluated using the cyclic voltammetry (CV) method. Such multi-technique investigation provides a new look into the role of solvation in micellization.

Solution properties of pluronics L44 or L [(PEO)(10)(PPO)(23)(PEO)(10)] and 10R5 or R [(PPO)(8)(PEO)(22)(PPO)(8)] were studied individually as well in their binary mixtures in aqueous medium. The critical micelle concentration (CMC), critical micelle temperature, and cloud point (CP) were determined. Ideal and nonideal behaviors of their mixtures in the formation of CMC and CP were observed; the energetics of the studied processes were determined. Spectrophotometry, isothermal titration calorimetry and dynamic light scattering (DLS) methods were used for evaluations. Morphologies of the dispersed L, R, and their mixtures along with their polydispersities were determined from DLS measurements. Atomic force microscopy was also employed. The interfacial properties of L and R were investigated forming Langmuir monolayers in a surface balance. The surface pressures (π) generated by the compounds were moderate, the area per molecule was higher for R than L. R has shown antibacterial activity against both gram positive and gram negative bacteria whereas L was inactive in this respect.

Mixed aquo-organic solvents are used in chemical, industrial, and pharmaceutical processes along with amphiphilic materials. Their fundamental studies with reference to bulk and interfacial phenomena are thus considered to be important, but such detailed studies are limited. In this work, the interfacial adsorption of sodium dodecylsulfate (SDS, C12H25SO4(-)Na(+)) in dioxane-water (Dn-W) and methanol-water (Ml-W) media in extensive mixing ratios along with its bulk behavior have been investigated. The solvent-composition-dependent properties have been identified, and their quantifications have been attempted. The SDS micellization has been assessed in terms of different solvent parameters, and the possible formation of an ion pair and triple ion of the colloidal electrolyte, C12H25SO4(-)Na(+) in the Dn-W medium has been correlated and quantified. In the Ml-W medium at a high volume percent of Ml, the SDS amphiphile formed special associated species instead of ion association. The formation of self-assembly and the energetics of SDS in the mixed solvent media have been determined and assessed using conductometry, calorimetry, tensiometry, viscometry, NMR, and DLS methods. The detailed study undertaken herein with respect to the behavior of SDS in the mixed aquo-organic solvent media (Dn-W and Ml-W) is a new kind of endeavor.

Individual amphiphiles, polymers, and colloidal dispersions influenced by temperature, pH, and environmental conditions or interactions between their oppositely charged pairs in solvent medium often produce solvent-rich and solvent-poor phases in the system. The solvent-poor denser phase found either on the top or the bottom of the system is called coacervate. Coacervates have immense applications in various technological fields. This review comprises a concise introduction, focusing on the types of coacervates, and the influence of different factors in their formation, structures, and stability. In addition, their physicochemical properties, thermodynamics of formation, and uses and multifarious applications are also concisely presented and discussed.

Various micelle parameters viz., critical micelle concentration (CMC), counter-ion binding (b), aggregation number (N), hydrodynamic radius (R h ), micelle zeta potential (f) and energetic parameters, free energy of micellization (DG 0 m ), enthalpy of micellization (DH 0 m ) and entropy of micelle formation (DS 0 m ) were determined for sodium dodecylsulfate, and dodecyltrimethylammonium bromide in the presence of NaCl for the former and NaBr for the latter. Conductometry and calorimetry methods were used for the measurements of CMC and energetic parameters. The fluorimetric (static quenching) method was employed to determine N and dynamic light scattering to estimate R h and f. The conductometrically determined b was verified from the CMC values by calorimetry using the Corrin-Harkins equation. The results found for the two surfactants of identical tails but different head groups have been presented and discussed. A detailed report on the salt effect using salts containing counter-ions the same as those in the surfactant is found only limitedly in the literature.

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