Spontaneous bubble growths in liquids are usually triggered by rapid changes in pressure or temperature that can lead to liquid gas supersaturation. Here, we report alternative scenarios of the spontaneous growths of bubbles inside a high-saturation-vapor-pressure and high-air-solubility perfluorocarbon liquid (PP1) that were observed under ambient quiescent conditions. First, we investigate spontaneous bubble growth inside the single PP1 phase, which was left to evaporate freely. The bubble growth is explained by the difference in the PP1 vapor pressure inside the bubble and that above the freely evaporating PP1 interface. Next, we study the bubble growth inside the liquid PP1 covered with a layer of a second air-saturated immiscible liquid: low-air-solubility water or higher-air-solubility ethanol. In both cases, the bubble growth rates were accelerated, indicating mass transfer of air from the water or ethanol phases to the PP1 phase. The bubble growth rates significantly increase for bubbles trapped at the PP1–water or PP1–ethanol interfaces due to faster air diffusion through the thin PP1 liquid films separating the bubbles from the upper phases. Finally, we consider the case of bubbles inside millimeter-sized PP1 emulsion droplets in water or ethanol. The bubble growth inside the droplet leads to an increase in the PP1 droplet’s effective buoyancy and to the detachment of the droplets from the substrate. The observed bubble growth rate in the case of emulsion droplets was much faster for PP1 droplets in ethanol than for PP1 droplets in water (minutes vs hours). The underlying physical mechanism of the increase of bubble volumes is the spontaneous mass transfer of both air and PP1 vapor to the bubbles produced by a colloidal diffusion pump effect.

Hypothesis
Polyglycerol esters of fatty acids are generated via the esterification of a polydisperse mixture of polyglycerol with naturally derived fatty acids. The polymerization process of polyglycerol results in the production of various oligomers, ranging from di-, tri-, and higher-order forms, which contribute to the complexity of final products. The combination of complementary experimental techniques and adequate theoretical interpretations can reveal the wide variety of their physicochemical properties.

Experiments
The colloid and interface properties of polyglyceryl mono-laurate, mono-stearate, mono-oleate, and a mixture of mono-caprylate and mono-caprate esters solutions were characterized by measurements of the electrolytic conductivity, static and dynamic surface tension, aggregate and micelle sizes and distributions, thin liquid film stability and stratification, and solubility in aqueous and in oil phases. The formation, stability, and bubble size distribution of foams generated from polyglycerol esters aqueous solutions were systematically investigated.

Findings
The low concentrations of double-tail molecules and fatty acids in polyglycerol esters affect considerably their micellar, aggregation, and vesicle formations in aqueous solutions. The theoretical data interpretation of polyglycerol esters isotherms and thin liquid films data provide information on the adsorption energies, excluded areas per molecule, interaction parameters of molecules at interfaces, surface electrostatic potential, and the size of micelles. Polyglyceryl mono-oleate exhibits spontaneous emulsification properties. Short chain length polyglycerol esters have excellent foaming ability but relatively low foam stability. The optimal weight fractions of the short-chain polyglyceryl esters and polyglyceryl mono-stearate mixtures with respect to good foaminess and foam stability upon Ostwald ripening are obtained. The reported physicochemical characterization of the water-soluble polyglycerol esters could be of interest to increase the range of their applicability in practice.

Hypothesis: Methyl ester sulfonates (MES) show limited water solubility at lower temperatures (Krafft point). One way to increase their solubility below their Krafft points is to incorporate them in anionic surfactant micelles. The electrostatic interactions between the ionic surfactant molecules and charged micelles play an important role for the degree of MES solubility. Experiments: The solubility and electrolytic conductivity for binary and ternary surfactant mixtures of MES with anionic sodium alpha olefin sulfonate (AOS) and sodium lauryl ether sulfate with two ethylene oxide groups (SLES-2EO) at 5 °C during long-term storage were measured. Phase diagrams were established; a general phase separation theoretical model for their explanation was developed and checked experimentally. Findings: The binary and ternary phase diagrams for studied surfactant mixtures include phase domains: mixed micelles; micelles + crystallites; crystallites, and molecular solution. The proposed general phase separation model for ionic surfactant mixtures is convenient for construction of such complex phase diagrams and provides information on the concentrations of all components of the complex solution and on the micellar electrostatic potential. The obtained maximal MES mole fraction of transparent micellar solutions could be of interest to increase the range of applicability of MES–surfactants.

Different oils can be homogeneously dispersed in the network junctions of the separated bicontinuous micellar phases. Upon dilution, these dispersions spontaneously form nanoemulsions. The possibility of a micellar sponge phase formation in the case of mixtures with three anionic and two zwitterionic surfactants in the presence of divalent and monovalent salts is studied. The best results are obtained using sodium lauryl ether sulfate with 1 ethylene oxide group (SLES-1EO) and both cocamidopropyl betaine (CAPB) or N,N-dimethyldodecylamine N-oxide (DDAO) in the presence of an appropriate small amount of MgCl2 and CaCl2. Bicontinuous micellar phases can be produced also in high-salinity NaCl solutions. The bulk properties of these phases are independent of the concentration of the initial solutions from which they are separated, and their Newtonian viscosities are in the range from 0.3 Pa·s to 0.8 Pa·s. Both 8 wt% CAPB- and DDAO-containing sponge phases engulf up to 10 wt% limonene and spontaneously form nanoemulsion upon dilution with droplet sizes of 110–120 nm. Vitamin E can be homogeneously dispersed only in CAPB-containing saturated micellar network, and upon dilution, these dispersions spontaneously form nanoemulsions with smaller droplet sizes of 66 nm for both 8 diastereomers and 2 diastereomers mixtures of vitamin E.

The concentrated surfactant solutions have a wide application in industry, oil recovery, drug delivery, turbulent drag reduction, etc. The competition between the companies-producers has led to use of new kind of formulations to improve: washing action; skin and eye irritation; stability and durability; biodegradability; tolerance to hard water. Here, we present a review on the state of the art and our contributions to the molecular thermodynamic theory and experiment on the growth of giant micellar aggregates. Despite the considerable advances in theory and computer simulations, agreement with experimental data has been achieved only in isolated cases. Our predictive molecular thermodynamic approach accounts for the different contributions to the micellar scission energy in the case of nonionic, zwitterionic and ionic surfactant solutions and their mixtures. Excellent agreement was achieved between the theoretical model and experimental data for wormlike surfactant micelles at various concentrations of salt and temperatures. At high salt concentrations, the model also predicts loss of chemical equilibrium, which implies a transition to self-assemblies of other morphology or the onset of crystallization and phase separation. The results have applications for the design of new products and nanostructured materials.