Phase behavior of the orange essential oil/sodium bis(2-ethylhexyl)sulfosuccinate/water system

The ternary phase diagram for the orange essential oil (OEO)/sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/water system was constructed at 25 °C. It indicates a large single phase region, comprising an isotropic water-in-oil (W/O) microemulsion (ME) phase (L₂), a liquid crystal (LC) (lamellar or hexagonal) and a large unstable emulsion phase that separates in two phases of normal and reverse micelles (L₁ and L₂). In this communication the properties of the ME are investigated by viscosity, electric conductivity and small angle X-ray scattering (SAXS) indicating that the isotropic ME phase exhibits different behaviors depending on composition. At low water content low viscous “dry” surfactant structures are formed, whereas at higher water content higher viscous water droplets are formed. The experimental data allow the determination of the transition from “dry” to the water droplet structures within the L₂ phase. SAXS analyses have also been performed for selected LC samples.     

Cubic phase prepared in an anionic/amphoteric surfactant/oleic acid/decane/water system and the relationship with the neighboring phase

The formation, properties, and structure of discontinuous cubic phase in the pseudo-ternary system consisting of N'-carboxyethyl N'-hydroxyethyl N-aminoethyl dodecylamide (imidazoriniumbetain), sodium and triethanol amine salt of polyoxyethylene (1.5 mol) myristyl ether sulfate, oleic acid, decane, and water at a constant surfactant/water ratio of 4/6 were studied by means of small-angle X-ray scattering, freeze-fracture transmission electron microscopy, static light scattering, and dynamic rheology to gain an insight in its origin and interrelation with neighboring phases. It was found that the cubic phase occupied a rather wide region in a constructed ternary phase diagram, including from 25 to 45% of decane. Its properties and structural parameters varied with changing the oil content. The decane addition caused the swelling of spherical micellar aggregates. This resulted in an increase of their diameter up to 35 nm, which was ca. nine times larger than that of the initial micelles, and micellar volume fraction (packing fraction) up to 72 vol. %, which was close to the theoretically possible value of 74 vol. % for the close-packed spherical particles. The cubic phase was surrounded by a micellar L1 phase from the water-rich side (separated by a short two-phase region), two-phase region (cubic + oil) from the oil-rich side, and a lamellar phase from the surfactant-rich side. A transition from the L1 phase to the cubic state at the packing fraction of 60 vol. % was caused by an increase in the packing density of micellar aggregates, occurring with the decane addition. When it reached 72 vol. %, the oil started forming a separated phase owing to the inability of micelles to dissolve it. The important observation is that the adjacent phase from the surfactant-rich side was a lamellar one made up of flat bilayers. The preliminary data showed that the lamellar phase coexisted with cylindrical micelles in the intermediate two-phase region separating the cubic and lamellar phases.     

Surfactant-free oil/water and bicontinuous microemulsion composed of benzene, ethanol and water

<正>Generally,a microemulsion consists of oil,water,surfactant and sometimes cosurfactant.Herein,we report a novel suffactant-free microemulsion(denoted as SFME) composed of benzene,water and ethanol without the amphiphilic molecular structure of traditional surfactant.The phase behavior of the ternary system was investigated,finding that there were a single-phase region and a two-phase region in ternary phase diagram.The electrical conductivity measurement was employed to investigate the microregion of the single-phase region,and a bicontinuous microregion and a benzene-in-water(O/W) microemulsion microregion were identified,which was confirmed by freeze-fracture transmission electron microscopy(FF-TEM) observations.The sizes of the microemulsion droplets are in the range of 20-50 nm.     

Biocompatible lipidic formulations: phase behavior and microstructure

Biocompatible systems formulated for use in the food, cosmetic, and pharmaceutical fields are characterized. Ternary phase diagrams of mixtures of natural lipids (glycerol trioleate, glycerol monooleate, diglycerol monooleate, and lecithin) and water were investigated by means of optical microscopy in polarized light and by multinuclear NMR spectroscopy. All systems showed a microemulsion region at high oil content and a large area of coexistence of two liquid crystalline (hexagonal and lamellar) phases. 1H and 13C NMR self-diffusion measurements were used to characterize microstructural features of the microemulsions. On water dilution, the two-phase liquid crystalline region transforms into a creamy emulsion area where the droplets of water are stabilized by both the lamellar and the hexagonal phases, as indicated by 2H NMR measurements. Due to the very effective dispersing action of the two liquid crystalline phases, these emulsions show a high stability toward phase separation.     

Structural fluctuations in the lamellar phase of sodium decyl sulphate/decanol/water

We present a neutron scattering study of oriented samples for the lamellar phase of the ternary mixture sodium decyl sulphate/1-decanol/water. Diffuse scatterings are observed, around the Bragg reflections and away from them, which show that the structure of this lamellar phase deviates from the periodic stacking of infinite homogeneous lamellae of water and amphiphilic molecules usually proposed for the structure of lamellar phases. The nature of this deviation evolves with the soap/decanol ratio, according to the location of the sample in the lamellar domain of the phase diagram. In the middle of the domain the deviation relates to the organization of the lamellar stacking, without apparent modification of the structure of the lamellae of amphiphiles. Moving away from the middle, for higher soap/decanol ratios, the structure of the lamellae appears to be randomly perturbed, eventually by the presence of a few water regions piercing them. When the boundary of the lamellar domain is approached, for still higher soap/decanol ratios, the density of these peturbations increases and they start to be correlated over limited distances, within the lamellae and from lamella to lamella. The local symmetry of these short range correlations is such that these perturbations may be seen as structural fluctuations which may be seen as precursors of the transformation of the lamellar phase into a neighbouring phase on the phase diagram. This phenomenon is discussed briefly in relation to the structural fluctuations of the relative concentrations of sodium decyl sulphate and decanol within the aggregates.     

Phase equilibria and phase structure in the ternary systems sodium or potassium octanoate-octanoic acid-water

Two isotropic solution regions and several liquid crystalline regions occur in the ternary system sodium octanoate-octanoic acid-water at 20°C The solution regions are an aqueous solution and a solution of sodium octanoate and water in liquid octanoic acid. A region displaying one-dimensional lamellar structure is located in the center of the phase diagram. A region along the soap-water axis has a two-dimensional normal hexagonal structure. Another region at high octanoic acid content has a reversed hexagonal structure. Along the soap-fatty acid axis the acid-soap 2NaC₈:1HC₈ in crystalline state is found.X-ray and density findings for the various phases are presented, and structural parameters for the different liquid crystalline phases are estimated.The phase behavior of the potassium soap system is similar to that of the sodium system.The isothermal ternary phase diagram of a soap, the corresponding fatty acid and water provides information about the ionization state of the system, from the unionized fatty acid to the fully ionized soap.     

Shear-induced topology changes in liquid crystals of the soybean lecithin/DDAB/water system

The viscoelastic behavior of the two different liquid crystalline lamellar phases and the liquid crystalline cubic phase of the mixed soybean lecithin/DDAB system in water was studied through rheology, with mechanical parameters studied as a function of composition. The swollen or diluted lamellar region is formed by vesicles, and its characteristic flow curve presents two-power law regions separated by a region where viscosity passes through a maximum. Yield stress and shear-dependent flow behavior were also observed. The microstructure suffers transformation under shear stress, and rheological response shifts from thixotropic to antithixotropic loops. Similar rheological behavior has been observed for samples in the collapsed or concentrated lamellar region, at the water-rich corner of the phase diagram. Vesicle formation may therefore occur by shearing the initial stacked and open bilayers. However, concentrated lamellar samples in the water-poor part of the phase diagram are less sensitive to shear effects and show plastic behavior and thixotropy. All lamellar samples manifest high elasticity. The dynamic responses of both lamellar topologies, i.e., vesicles and open bilayers, are comparable and exhibit an infinite relation time. The bicontinuous cubic, liquid crystalline phase is highly viscous. Its dynamic response cannot be modeled by a Maxwell model.     

Interaction of sodium ions with cationic surfactant interfaces

The thermodynamically stable microemulsion and lamellar phases in the didodecyldimethylammonium bromide/water/n-decane ternary system were explored in the presence of NaBr to gain information on sodium ion-interface interactions. Experimental results, obtained by different NMR techniques, strongly suggest accumulation of sodium ions at the cationic interface. This apparently counterintuitive result is explained by invoking the dispersion potential experienced by the ions near the interface. A mechanism is proposed that can account for the dramatic shrinkage of the microemulsion phase region when an electrolyte is added.     

P NMR investigation of a ringing gel phase and adjacent phases

The temperature-surfactant concentration phase diagram was examined for the dodecyltrimethylammonium dimethylphosphate/3-methyl-3-methoxybutanol/water ternary system. The phase diagram contained a highly elastic gel phase which is known as a “ringing gel phase”. The ringing gel phase and adjacent phases in the ternary system were investigated by polarized optical microscopy, freeze-fracture transmission electron microscopy, and ³¹P NMR. Globular textures were observed in an optically isotropic gel phase. Since the globules were larger than those found in an isotropic solution, the texture consists of domains of aggregated units in the cubic (I₁) phase. Structure units of domains are equivalent to microemulsions which are constructed by surfactant molecules and swollen by alcohol in the isotropic (L₁) phase. Characteristic polarized microscopic textures were visualized in two phases with higher surfactant concentrations. These phases were identified as being hexagonal (H₁) and lamellar (L) liquid crystals which was confirmed by transmission electron microscopy. The ³¹P NMR signal of the ringing gel showed a sharp singlet the same as that of the L₁ phase, indicating the fully averaged anisotropic interaction of the aggregates. The characteristic NMR signals of the anisotropic hexagonal and lamellar liquid crystal phases displayed chemical shielding with an asymmetric lineshape.     

Phase behavior of a DNA-based surfactant mixed with water and n-alcohols

The self-assembly behavior of a cationic surfactant (dodecyltrimethylammonium, DTA) with DNA as counterion in mixtures of water and n-alcohols (decanol, octanol, hexanol, butanol, and ethanol) was investigated. The phase diagrams were established and the different regions of the phase diagram characterized with respect to microstructure by (2)H NMR, small-angle X-ray scattering (SAXS), and other techniques. The DNA-DTA surfactant is soluble in all of the studied alcohols, showing increased solubility from decanol down to ethanol. All of the phase diagrams are analogous with respect to the occurrence of liquid crystalline (LC) regions, but the area of the LC region increases as one goes from decanol to ethanol. In all phase diagrams, hexagonal phases (of the reversed type) for the alcohol-rich side and lamellar phases for the other side were detected. For balanced proportions of the components, there is a coexistence of the lamellar and the hexagonal phase, here detected with a double quadrupole splitting in the (2)H NMR spectra. The correctness of the phase diagrams is confirmed by the fact that along the tie-lines the splitting magnitude remains nearly constant. All of the alcohols except for ethanol act as cosurfactants penetrating the DNA-DTA film. Adding salt to the ternary mixtures causes an increase in the unit cell dimension of the lamellar and the hexagonal phases. The phase diagram becomes more complicated when butanol is used for the alcohol phase. Here, there is the occurrence of a new isotropic phase with some properties analogous to those of the disordered sponge (L3) phase obtained for simple surfactant systems.     

Aqueous phase behavior of tetraethylene glycol decanoyl ester (C9COE4) and Ether (C10E4) investigated by nuclear magnetic resonance spectroscopic techniques

The binary phase diagram of tetraethylene glycol decanoyl ester (C9COE4) was investigated in the micellar region by PGSE-NMR (pulse field gradient spin echo nuclear magnetic resonance) and in the lamellar liquid crystalline state by 2H NMR. Its behavior was compared to the ether counterpart, tetraethylene glycol decanoyl ether (C10E4), whose phase diagram is well-described. The determination of the self-diffusion coefficient as a function of concentration permitted not only a determination of the critical micellar concentration (cmc) values but also the determination of the size and shape of micelles formed by both compounds. The evolution of the self-diffusion coefficients in the vicinity of the cloud point was also studied, showing no micellar growth with increasing temperature. 2H NMR analyses at the border of and within the liquid crystalline region gave an insight into the lamellar phase structure. We investigated in detail the lamellar phase of both compounds by comparing the values of quadrupolar splittings (Deltanu) measured under the same conditions. Lower Deltanu values were found for the ester compared to the ether: since the ester probably binds more water than the ether, these lower Deltanu values would indicate a lower order parameter in the liquid crystal phase. NMR techniques, either PGSE-NMR or 2H NMR, were confirmed as useful tools to characterize aqueous phase behavior of surfactants, providing supplementary information to the classical techniques such as visual observations, polarized optical microscopy (POM), and surface tension measurements. They also provide a unique insight into the molecular organization in the different phases formed.     

Temperature-induced phase separation in pseudoternary mixtures of Triton X-100–butanol–kerosene–water

The transparent Winsor IV domain in the phase diagram of the mixtures of emulsifier (Triton X-100 and butanol), oil (kerosene), and water is found to be 34% of the total phase diagram in presence of emulsifier with surfactant:cosurfactant::1:1, and is water dominant. Increase in cosurfactant/surfactant ratio inverts the Winsor IV domain to become oil rich. The plot of conductance of the microemulsions prepared by substituting water by brine against water content depicts the existence of three distinct phases like oil-in-water, bicontinuous, and water-in-oil microemulsion in the phase diagram. The phase contrast micrographs of the mixtures of different compositions in these three different phases reveal the existence of microdroplets of oil dispersed in water and water dispersed in oil. Further, the dynamic light scattering studies of these solutions reveal an inhomogeneity in the size distribution of the droplets. A temperature-induced clouding in the microemulsion domain leading to phase separation has been observed. Additives like glucose, sucrose, and sodium chloride decrease the cloud point (CP), while addition of ammonium thiocyanate increases it. A quantitative relationship of the clouding temperature with the composition of the microemulsion has been established. With increase in oil and emulsifier, the cloud point of the microemulsion increases. The separated phases after the clouding have been used for preconcentration of water-soluble metal ions as well as oil-soluble dyes. The turbid systems on heating led to separation into three isotropic phases which are found to be stable at ambient temperature. The stability of these phases is ascribed to the formation of stable microemulsions by mass transfer from one phase to other.     

Phase equilibria and structures in ternary systems of a cationic surfactant (C16 TABr or (C16 TA)2SO4), alcohol,and water

The dependence of alcohol chain length on the isothermal phase behavior of the ternary systems hexadecylrrimethylammonium bromide/alcohol/water has been investigated. A liquid crystalline phase (the normal hexagonal one) occurs in the phase diagrams along the surfactant/water axis and this phase extends in the interior of the diagrams.When the alcohol is methanol, ethanol or butanol, there is in the ternary phase diagram a continuous solution region from the water to the alcoholic corner, and in the butanol case, in addition, a small region of lamellar liquid crystalline phase in the interior of the diagram. When the alcohol chain length is increased, the continuous solution region is divided into two subregions, an aqueousL ₁ and an alcoholicL ₂. The lamellar phase occupies the center of the phase diagrams and has the capability to incorporate large amounts of water under one-dimensional swelling. On the alcoholic side of the lamellar phase occur a reversed hexagonal liquid crystalline phase and a cubic liquid crystalline phase in the octanolic system; in the decanolic system the cubic phase is missing, but instead another liquid crystalline phase, presumably with rod-structure, occurs in addition to the reversed hexagonal phase.In a decanolic system where the monovalent bromide ion is replaced by the divalent sulphate ion there are the same solution regionsL ₁ andL ₂, and phase regions with liquid crystalline normal hexagonal and lamellar structures. The lamellar phase has lost much of its capability of incorporating water. That is in analogy with the conditions in anionic systems where the counterion charge has been increased. There is no reversed hexagonal phase, but on the alcoholic side of the lamellar phase, there is the same foreign liquid crystalline phase with a presumed rod-structure as in the monovalent system.     

The water/n-octane/octyl-beta-D-glucoside/1-octanol system: phase diagrams and phase properties

The partial phase diagram of D2O/n-octyl-beta-D-alkyl-glucoside(C8G1)/n-octane has been determined at T=25 degrees C. The diagram contains a funnel-shaped micellar phase originating from the water corner of the phase diagram D2O/C8G1 with the stem forming a narrow three-phase region, in which the three phases in equilibrium are two microemulsions of similar composition and an excess oil phase. The microemulsions have been characterized with NMR self-diffusion measurements. At high surfactant concentration and no or low n-octane content, branched micelles exist. As the n-octane content is increased, discrete micelles are formed. Upon further addition of n-octane, the phase separation into two microemulsion phases is induced. Possible mechanisms causing the phase separation are discussed. The phase diagram of D2O/(C8G1)/1-octanol has been determined at 25 degrees C. Ten different phase regions were identified. The phases have been characterized with SAXS and deuterium heavy water NMR, and the swelling of the lamellar phase was investigated with SAXS.     

Phase behavior of the lecithin/water/isooctane and lecithin/water/decane systems

The isothermal pseudo-ternary-phase diagram was determined at 25 degrees C for systems composed oflecithin, water, and, as oil, either isooctane or decane. This was accomplished by a combination of polarizing microscopy, small-angle X-ray scattering, and NMR techniques. The lecithin-rich region of the phase diagram is dominated by a lamellar liquid-crystalline phase (Lalpha). For lecithin contents less than 60% and low hydration (mole ratio water/lecithin = W0 < 5.5), the system forms a viscous gel of branched cylindrical reverse micelles. With increase in the water content, the system phase separates into two phases, which is either gel in equilibrium with essentially pure isooctane (for lecithin < 25%) or a gel in equilibrium with Lalpha (for lecithin > 25%). These two-phase regions are very thin with respect to water dilution. For 8 < W0 < 54 very stable water-in-oil emulsions form. It is only after ripening for more than 1 year that the large region occupied by the emulsion reveals a complex pattern of stable phases. Moving along water dilution lines, one finds (i) the coexistence of gel, isooctane and Lalpha, (ii) equilibrium between reverse micelles and spherulites, and, finally, (iii) disconnected reverse micelles that fail to solubilize water for W0 > 54. This results in a Winsor II phase equilibrium at low lecithin content, while for lecithin > 20% the neat water is in equilibrium with a reverse hexagonal phase and an isotropic liquid-crystalline phase. The use of the decane as oil does not change the main features of the phase behavior.     

Emulsifying potency of new amino acid-type surfactant (II): stable water-in-oil (W/O) emulsions containing 85 wt% inner water phase

The ternary phase diagram for N-[3-lauryloxy-2-hydroxypropyl]-L-arginine L-glutamate (C12HEA-Glu), a new amino acid-type surfactant, /oleic acid (OA)/water system was established. The liquid crystal and gel complex formations between C12HEA-Glu and OA were applied to a preparation of water-in-oil (W/O) emulsions. Stable W/O emulsions containing liquid paraffin (LP) as the oil and a mixture of C12HEA-Glu and OA as the emulsifier were formed. The preparation of stable W/O emulsions containing 85 wt% water phase was also possible, in which water droplets would be polygonally transformed and closely packed, since the maximum percentage of inner phase is 74% assuming uniformly spherical droplets. Water droplets would be taken into the liquid crystalline phase (or the gel complex) and the immovable water droplets would stabilize the W/O emulsion system. The viscosity of emulsions abruptly increased above the 75 wt% water phase (dispersed phase). The stability of W/O emulsions with a lower weight ratio of OA to C12HEA-Glu and a higher ratio of water phase was greater. This unusual phenomenon may be related to the formation of a liquid crystalline phase between C12HEA-Glu and OA, and the stability of the liquid crystal at a lower ratio of oil (continuous phase). W/O and oil-in-water (O/W) emulsions containing LP were selectively prepared using a mixture of C12HEA-Glu and OA since the desirable hydrophile-lipophile balance (HLB) number for the emulsification was obtainable by mixing the two emulsifiers.     

辛烷基苯酚聚氧乙烯醚与正癸醇层状液晶的有序性及层状结构

Order character and lamellar structure of TritonX 100/n C10H21OH/H2O lamellar liquid crystal were investigated. Partial phase diagram of TritonX 100/C10H21OH/H2O was measured at 25℃ by the polarizing microscope, and lamellar structure of the lamellar liquid crystal was verified by the 2H NMR spectra. The ESR spin probe method was used to detect the changes in the lamellar liquid crystal. A stearic acid, 5 doxylstearic acid, was used as the spin probe. The values of hyperfine coupling constant and order parameter of lamellar liquid crystal in the phase diagram were calculated. The values of the hyperfine coupling constant with different composition were almost unchanged. It indicates that the micropolarity of the lamellar liquid crystal is very similar. The order parameter decreases with the increasing water content in lamellar liquid crystal. It can be explained by considering that: First, though the penetration is determined at the given weight ratio of C10H21OH to TritonX 100, the absolute water content penetrated into the amphiphile bilayer increases with the increasing of the water content. Second, the thickness of the solvent also increases, which makes the force between layers weaker. The results also showed that order parameter of lamellar liquid crystal increased with TritonX 100 content, which may be explained from the fact that the water content penetrated into the amphiphile bilayer decreases relatively and the molecules in the amphiphile bilayer are made tighten. The interlayer spacing of lamellar liquid crystal was determined by small angle X ray diffraction. The penetration ratio of water in the lamellar liquid crystal was calculated. It was about 50%.     

Phase Behavior and Formulation of Palm Oil Esters o/w Nanoemulsions Stabilized by Hydrocolloid Gums for Cosmeceuticals Application

Palm oil esters (POEs) are wax esters derived from palm oil and cis-9-octadecen-1-ol. The excellent wetting behaviour of the esters without the oily feel make them have great potentials in the manufacture of cosmeceutical and pharmaceutical products. However, little is known about their phase behaviors in ternary systems. The purpose of this investigation was to construct phase diagram of the POEs and mixed surfactants and to consequently select nanoemulsions composition for further studies. The preparation and characterization of oil-in-water nanoemulsions stabilized by hydrocolloid gums were then studied. Two types of nonionic surfactants were selected, namely Tween 80 (T80) and Span 80 (S80). Ternary phase diagram of POEs:Tocotrienol/T80:S80 (80:20)/water system was constructed at 25.0 ± 0.5°C. The emulsification properties of 2 hydrocolloids gum (xanthan gum, carbopol ultrez 20 copolymer) were investigated. Gum dispersions were prepared in water (0.8%) and emulsified with 30% oil using a Polytron homogenizer. The flow curve of the emulsions always exhibited shear thinning behavior and obeys the power law viscosity. The emulsions with carbopol ultrez 20 copolymer was the most stable emulsions which composed of very small oil droplets (50% < 142.43 nm) with a narrow size distribution.     

无表面活性剂微乳液体系：N,N－二甲基甲酰胺/呋喃甲醛/水

通常微乳液一般由四个组分构成：水相、油相、表面活性剂和助表面活性剂。本文报道了一种不含表面活性剂的微乳液体系(简称SFME),由呋喃甲醛(油相),水和N,N－二甲基甲酰胺(DMF)三组分构成,不含传统的表面活性剂。对其相行为进行了研究,发现存在一个单相微乳液区和一个两相平衡区。采用电导率法和冷冻蚀刻电镜(FF-TEM)考察了单相区域中微乳液的微结构,结果表明可分为油包水(O/W)、双连续(BC)和水包油(W/O)三个区域。液滴直径介于40-70nm。     

STUDIES ON THE PHASE DIAGRAM OF THE SURFACTANT/1-PENTANOL / WATER TERNARY SYSTEM II: THE LIQUID CRYSTALLINE PHASE

The phase behavior of liquid crystalline in the ternary system of dodecyl dimethyl ammonium hydroxyl propyl sulfonate(DDAHPS)/1pentanol(C5HnOH) / water deuteron(D₂O) has been investigated by polarizing optical microscopy, ²H NMR spectroscopy methods. The results indicate that two kinds of liquid crystals (the lamellar, and the hexagonal) exist in the liquid crystalline phase region. In this paper, we also use the polarized Raman spectroscopy method to measure the values of the order/ disorder parameters and the values of the environment polarity parameters for the samples selected from the liquid crystalline phase region, and compare these two parameters of the samples with those of solid state DDAHPS and liquid state pentan-l-ol.