Phase behavior of pseudoternary brine/alkane/alcohol-secondary alkanesulfonates systems

Dodecanesulfonates (isomer mixtures) have been synthesized by the process developed in our laboratory. First, pseudoternary phase diagrams of water or (brine) decane/dodecanesulfonates-butan-1-ol systems were drawn and compared with those of a commercial sample (Hostapur 60). In the presence of NaCl, a three-phase region (Winsor III) appears for the two systems, and is larger with the home-made surfactants. This region is interesting in enhanced oil recovery because it leads to very low interfacial tensions. Then, the behavior of the Winsor III region was investigated as a function of the alcohol/surfactant mass ratio (C/T). At a constant salinity (2.5 mass% NaCl) a value of 2 for C/T gives the best compromise for a larger WIII region with both systems. For this ratio, optimal salinity values of 1.55 and 1.65 mass% for our sample and Hostapur 60, were found, respectively.     

The solid-liquid phase diagrams of binary mixtures of even saturated fatty alcohols

This study is part of a work developed in the author's research group on the solid-liquid equilibrium of fatty substances. The phase diagrams of the following fatty alcohol systems were determined by differential scanning calorimetry (DSC): 1-octanol + 1-dodecanol, 1-octanol + 1-tetradecanol, 1-decanol + 1-tetradecanol, 1-decanol + 1-hexadecanol and 1-dodecanol + 1-octadecanol. The liquidus lines of three of these systems were previously reported in the literature but the other two systems were never published. Moreover other transitions, in addition to the eutectic temperature, were also detected in all the systems. A region of solid solution at the extreme left of the phase diagrams was observed for all the binary mixtures. Polarized light microscopy was used to complement the characterization of the systems for a full grasp of the phase diagrams. The solid-liquid equilibrium was modeled using the Margules 2-suffix, Margules 3-suffix, NRTL and UNIFAC Dortmund equations.     

Binary melting phase diagrams of nifedipine-PEG 4000 and nifedipine-mannitol systems

The phase diagrams of nifedipine-polyethylene glycol (PEG) 4000 and nifedipine-mannitol systems have been determined. Heating experiments on thermodynamically equilibrated co-melts revealed eutectic behaviour for nifedipine-PEG 4000 mixtures, with the composition of the eutectic point between 40 and 45%w/w of nifedipine. These observations were supported by optical and hot stage microscopy. Nifedipine and mannitol were negligibly miscible in the solid-state, behaving as a binary system with monotectic characteristics. Application of phase diagrams to the production of solid dispersions is shown to be rational, since they provide valuable information on the state of the binary systems under preparation. This revised version was published online in July 2006 with corrections to the Cover Date.     

多组分体系相图中的杠杆原理形式

讨论了两相和三相多组分体系中杠杆原理的两种形式。对两组分体系,利用三相线上的杠杆原理关系式和凝固点降低公式,解释了熔化物体系冷却过程中的步冷曲线。另外,还讨论了三组分体系相图中,同一直线段上三个物系点之间的类杠杆原理关系式。该关系式可以用于不同浓度溶液的配制和三相体系相图的绘制。     

Studies on the Phase Behavior of Beta‐cypermethrion Microemulsion

The phase behavior of the system of surfactant SAA [0203B, nonionic surfactant 700# and methanol (weight ratio=6∶1∶1)]/mixed oil [beta‐cypermethrion, dimethyl benzene and cyclohexanone (weight ratio=2∶2∶1,or 0∶2∶1)]/water [distilled water (0 mg/L), or standard water (342 mg/L), or ultra‐hard water (500 mg/L)] has been studied in a pseudoternary phase diagram at 25 ± 1°C. Our results indicated that the isotropic monophasic area in the phase diagrams decreased significantly as the beta‐cypermethrion was added in the oil phase. In an attempt to the microemulsion electrical condectivity can be define regions corresponding to three structure states W/O, B.C., and O/W type in the microemulsion domain. The influence of beta‐cypermethrion on their regions sequences B.C. > O/W?W/O type. This work will be beneficial to improving the quality of beta‐cypermethrion microemulsion and make it more competitive in the market.     

Tuning high aqueous phase uptake in nonionic water-in-oil microemulsions for the synthesis of Mn-Zn ferrite nanoparticles: phase behavior, characterization, and nanoparticle synthesis

In this work, the formation of water-in-oil (w/o) microemulsions with high aqueous phase uptake in a nonionic surfactant system is investigated as potential media for the synthesis of Mn-Zn ferrite nanoparticles. A comprehensive study based on the phase behavior of systems containing precursor salts, on one hand, and precipitating agent, on the other hand, was carried out to identify key regions on (a) pseudoternary phase diagrams at constant temperature (50 °C), and (b) pseudobinary phase diagrams at constant surfactant (S):oil(O) weight ratio (S:O) as a function of temperature. The internal structure and dynamics of microemulsions were studied systematically by conductivity and self-diffusion coefficient determinations (FT PGSE (1)H NMR). It was found that nonpercolated w/o microemulsions could be obtained by appropriate tuning of composition variables and temperature, with aqueous phase concentrations as high as 36 wt % for precursor salts and 25 wt % for precipitating agent systems. Three compositions with three different dynamic behaviors (nonpercolated and percolated w/o, as well as bicontinuous microemulsions) were selected for the synthesis of Mn-Zn ferrites, resulting in nanoparticles with different characteristics. Spinel structure and superparamagnetic behavior were obtained. This study sets firm basis for a systematic study of Mn-Zn ferrite nanoparticle synthesis via different scenarios of microemulsion dynamics, which will contribute to a better understanding on the relationship of the characteristics of the obtained materials with the properties of the reaction media.     

Effect of Addition of Cosurfactant on the Phase Behaviour of Oil-in-water Aminosilicone Oil Microemulsion

Stable and transparent aminosilicone oil microemulsion of the average particle size below 0.05 micron was prepared. The interaction of the aminosilicone oil, water, complex surfactants and cosurfactant was studied by part pseudotemary phase diagram. The effect of cosurfactants (such as alcohol) and the mechanism of its effect on the phase behaviour of the pseudotemary system were investigated.     

Preparation of Fe3O4 magnetic fluid by one-step method with a microemulsion reactor

A W/O microemulsion was prepared with Span80-PS (petroleum sulfonate) as complex emulsifier, isopropanol as cosurfactant and kerosene as oil phase. The optimal constituents of microemulsion were found from pseudoternary phase diagrams: the mass ratio of Span80 to PS was 4:1 and complex surfactant to cosurfactant was 1:1. The Fe₃O₄ magnetic fluid was obtained by one-step method with the W/O microemulsion as microreactor to synthesize magnetic nanoparticles (reaction temperature was 30 °C and reaction time was 5 h) and kerosene as carrier liquid. The magnetic fluid was investigated by TEM, XRD and fluorescence microscope. The magnetism was determined by Gouy magnetic balance. The average particle size of Fe₃O₄ was 7.4 nm, and magnetic particles were well-dispersed. The stable Fe₃O₄ magnetic fluid with good magnetism may be produced by one-step method in the W/O microemulsion. Accordingly, the traditional preparation method of magnetic fluid can be simplified greatly. __________ Translated from Chinese Journal of Applied Chemistry, 2005, 22 (7) (in Chinese)     

Volume study on the exclusion of lithium naphthylsulfonate from lithium decylsulfonate micelles

Densities of aqueous solutions of lithium 1-naphthylsulfonate (1-LiNSO)–lithium decylsulfonate (LiDeSO) and 2-LiNSO–LiDeSO mixtures were measured as a function of total molality and composition of the mixtures. The partial derivative of the solution with respect to the total molality was calculated for the monomer and micellar regions. It was found that the values of the partial derivative are larger for the 2-LiNSO–LiDeSO system than for the 1-LiNSO–LiDeSO system. This fact is attributable to the larger value of the partial molar volume of monomer of 2-LiNSO than that of 1-LiNSO. For the two systems, the micellar molar volume of the mixtures varied linearly with the composition from the partial molar volumes of 1- and 2-LiNSO in their single systems to the micellar molar volume in the single LiDeSO system. Miscibility of the solutes in the mixed micelles was examined by drawing the critical micelle concentration (CMC) vs composition diagrams. The diagrams for the 1- and 2-isomers coincided with each other and showed that molecules of 1- and 2-LiNSO are excluded from the micelles. The contribution of the micelle-unforming component to the volume of micelle formation is positive and large because of the exclusion from the micelles. On the other hand, the contribution of the micelle-forming component to the volume of micelle formation is unchanged. The dependence of the monomer molalities of LiNSO and LiDeSO on the total molality, evaluated by means of the CMC vs composition diagrams, substantiated the validity of the approximations used in the derivation of the equations in this study.     

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.     

Thermal Analysis of Solid-Solid Interactions in Binary Mixtures of Alkylcyclohexanes Using DSC

Differential scanning calorimetry (DSC) was used to construct phase diagrams of binary mixtures of alkylcyclohexanes and to characterize metastable phases formed in the binary mixtures. The experimentally measured liquidus curves were compared to the liquidus curves calculated using ideal solution theory. The measured phase diagrams of pentadecylcyclohexane/nonadecylcyclohexane and octadecylcyclohexane/nonadecylcyclohexane binary mixtures are consistent with theoretical phase diagrams constructed based on the assumption that these mixtures form eutectic systems. It was also observed that a metastable phase formed in some binary mixtures of pentadecylcyclohexane/nonadecylcyclohexane under fast cooling conditions. It is hypothesized that this metastable phase recrystallizes into the eutectic phase upon heating. This revised version was published online in July 2006 with corrections to the Cover Date.     

CTAB/正丁醇-正辛烷-水和盐水的拟三元体系相图及微乳液微观结构的电导研究

绘制了CTAB/正丁醇-正辛烷-水和Al(NO₃)3(或Na2WO4)盐水拟三元体系的35℃相图.用电导法并结合电解质理论讨论了微乳液的微观结构,将整个微乳液单相区分为W/O微乳区、O/W微乳区和B.C.双连续区,并且用渗滤理论确定了一个分散相质点为W/O球状结构的反胶团微乳液区.     

The case of missing incommensurate smectic A phases

Two binary mixtures of polar liquid crystal materials were previously reported to exhibit three incommensurate smectic A phases predicted for such materials on the basis of phenomenological theory. Results of our recent high-resolution X-ray scattering experiments show that no incommensurate phases exist in the two systems. Wide coexistence regions are found at first order transitions between various frustrated smectic phases of these mixtures. These regions were previously identified as the incommensurate smectic A phases. The phase diagrams of the two systems determined with high-resolution X-ray technique are shown to be in excellent agreement with Baroisa-Prost-Lubensky theory.     

Thermophysical behaviour of monofunctional acrylate and liquid crystal systems

The phase behavior of monofunctional acrylate and low molecular weight nematic liquid crystals (LC) is considered. Systems involving the monomeric 2-ethylhexylacrylate (2-EHA), the eutectic LC mixture known as E7 and the 4-cyano-4^′-n-pentyl-biphenyl (5CB) are investigated. A similar investigation is performed on mixtures involving a polymer poly-2-EHA with molecular weight M_w=48,000 g/mol and both LCs. The experimental phase diagrams are established using polarized optical microscopy and analyzed using a theoretical formalism which combines the Flory-Huggins theory of isotropic mixing and the Maier-Saupe theory of nematic order. The results lead to characterization of the miscibility of E7 and 5CB with monomeric and analogous polymeric 2-EHA systems.     

Phase equilibria and photopolymerisation-induced phase transitions of mesogenic diacrylate monomer and low molecular mass liquid crystal mixture

Experimental phase diagrams of binary mesogenic mixtures of reactive mesogenic diacrylate (RM257) monomer and low molar mass liquid crystals (E7) were determined by means of differential scanning calorimetry and optical microscopy. The combined free energy densities of Flory–Huggins for liquid–liquid demixing, Maier–Saupe for nematic ordering, and phase field free energy for crystal solidification was proposed to describe the phase diagrams of the starting E7/RM257 mixtures. The phase diagram thus constructed is an ideal mixing type, exhibiting a narrow loop of isotropic + nematic (I + N) coexistence region followed by the crystal + nematic (Cr1 + N) region in descending order of temperature. Of particular interest is the permanent fixation of the mesophase structures upon photopolymerisation of neat RM257 in the corresponding nematic and crystalline phases. Upon photopolymerisation of a low RM257 content mixture in both isotropic and nematic states, the nematic–isotropic transition of E7 was found to persist. The permanent structural anchoring is seen upon photo-curing of the 90/10 RM257/E7 mixture in the crystalline state.     

Correlation of the volumes and heat capacities of solutions with their solid-liquid phase diagrams

Liquid systems which have strong non-idealities, as seen from their thermodynamic properties, often show evidence of these interactions in the solid-liquid phase diagrams. This suggests that some of the structures present in the solid state can persist in the solution state, on a time average, up to temperatures much higher than the melting point. Volumes and heat capacities of typical systems were either taken from the literature or measured to illustrate this correlation with the phase diagrams. With mixtures of aprotic solvents which show nearly-ideal simple eutectic phase diagrams, the properties of the solutions are also nearly ideal. Examples of systems investigated which show strong non-idealities are ionic surfactant solutions, alcohol-water mixtures, chloroform-triethylamine mixtures and lithium salts in aprotic solvents.Paper written in the honor of Loren Hepler on the occasion of his retirement.     

Effect of external electrical field on phase behavior and morphology development of polymer dispersed liquid crystal

Phase diagrams for mixtures of liquid crystal (LC)/monomer with and without an external electrical field applied have been established using polarized light microscope (PLM).The (isotropic + nematic) coexistent phase region and (isotropic + isotropic) phase boundary of LC/monomer mixtures were observed to shift upward to higher temperatures when the external electrical field exists. It was found that the electrical field applied during the cross-linking polymerization has a significant influence on the phase diagrams for the LC/polymer mixtures by rendering the coexistent phase regions shift upward to higher temperatures. The influence of the external electrical field on the processes of the isotropic-isotropic phase separation and liquid crystal ordering in PDLC formation has also been investigated. The results revealed that both the processes could be highly accelerated by the electrical field.     

Formulation and physicochemical characterization of imwitor 308 based self microemulsifying drug delivery systems

Self Microemulsifying Drug Delivery Systems (SMEDDS) are a novel alternative to the conventional transdermal delivery systems. SMEDDS are water-free systems, made up of oils and surfactants that can readily form a microemulsion upon dilution within an aqueous medium. Before SMEDDS can be used as a drug delivery system it is necessary to investigate the internal microstructure of the resulting microemulsion. Novel Imwitor 308 based SMEDDS were prepared and investigated. Phase behaviour of the comprising components was investigated through the construction of pseudoternary phase diagrams. The formed systems were characterized using visual inspection, measurement of electrical conductivity, viscosity and droplet size. Amongst the pseudoternary systems investigated, IPM/Cremophor EL (50% w/w)/Imwitor (50% w/w) and Myritol 318/Tween 85 (64% w/w)/ Transcutol P (20% w/w)/Imwitor (16% w/w) possessed the largest microemulsion area. Electrical conductivity and viscosity studies depict structural transitions from w/o microemulsion to bicontinuous or o/w microemulsion around 20-35% water. This was further supported by the droplet size and Fourier transform (FT)-IR measurements. The FT-IR data suggests that below the percolation threshold (ψ(C)) the water molecules are mainly bounded to the surfactant head group (bound water). Above this value, water molecule move to the outer phase of the microemulsion mainly interacting with each other though hydrogen bounding (free water). It was also found that pseudoternary systems with water content of less than 30% were stable at 32°C. Such systems may form stable microemulsion upon contact with the skin. Absorption of water may also result in a supersaturated solution with enhanced transdermal flux.     

Characterization of the Liquid-Gas Interface of Aqueous Systems Containing a Derivative from Castor Oil

An anionic surfactant, synthesized with ricinoleic acid from castor oil, was obtained and its behavior in terms of microemulsion formation (via pseudo-ternary diagram analysis) and liquid-gas surface tension (both for microemulsions and pure surfactant-water systems) was determined as a function of temperature and NaCl concentration in the aqueous phase. Microemulsions were formed by using butanol as co-surfactant and kerosene as the oil phase. Concerning the pseudoternary diagrams, the increase in NaCl concentration resulted in a decrease in the Winsor IV region, which was correlated to a possible occurrence of nonmicellar aggregates, induced by the high concentration of NaCl in the aqueous phase. Surface tension measurements also indicated that at the very high NaCl concentrations used there could be the formation of surfactant aggregates. The oil phase in microemulsionated systems decreased surface tension (but increased CMC): Possible interactions between isolated surfactant molecules and molecules from the oil phase were used to explain these results.