A crossover quasi-chemical nonrandom lattice fluid model for pure carbon dioxide and hydrocarbons

Thequasi-chemical nonrandom lattice fluid model is capable of describing thermodynamic properties for complex systems containing associating fluids, polymer, biomolecules and surfactants, but this model fails to reproduce the singular behavior of fluids in the critical region. In this research, we used the quasi-chemical nonrandom lattice fluid model and combined this model with a crossover theory to obtain a crossover quasi-chemical nonrandom lattice fluid model which incorporated the critical scaling laws valid asymptotically close to the critical point and reduced to the original quasi-chemical nonrandom model far from the critical point. The crossover quasi-chemical nonrandom lattice fluid model showed a great improvement in prediction of the volumetric properties and second-order derivative properties near the critical region.     

APPLICATION OF THEORETICAL MODELS TO THE ESTIMATE OF M1CROEMULSIONS PROPERTIES PART I TERNARY SYSTEMS

A model has been developed which adequately describes the phase behavior of alcohol in an oil phase. The model has been also extended to quaternary systems containing a surfactant component.     

APPLICATION OF THEORETICAL MODELS TO THE ESTIMATE OF M1CROEMULSIONS PROPERTIES PART I TERNARY SYSTEMS

A model has been developed which adequately describes the phase behavior of alcohol in an oil phase. The model has been also extended to quaternary systems containing a surfactant component.     

The Phase Transformation Mechanism of Bentonite-Stabilized and Cetyltrimethylammonium Bromide-Stabilized Emulsions and Application in Reversible Emulsification Oil-Based Drilling Fluids

We obtained a reversible emulsion system induced by bentonite solid particles and surfactant Cetyltrimethylammonium bromide (CTAB, whose critical micelle concentration (CMC) value is 9.21 × 10⁻⁴ mol L⁻¹). In this study, the zeta potential and contact angle were used to characterize surface wettability of bentonite solid particles in the process of phase transmission behavior. The adsorption amount was calculated at different CTAB concentrations, and then the adsorption isotherm of surfactant CTAB at bentonite solid particles was also studied to confirm the adsorption behavior and adsorption layer structure. The electrical conductivity and microscopic analysis were employed to characterize the phase inversion behavior of emulsion. The results show that the wettability of bentonite particles can be reversed by changing the CTAB concentration, and then the two phase transition behavior of bentonite emulsion can be induced. Additionally, the surfactant CTAB can be used in oil-based drilling fluid systems for the inversion of the emulsion type. The research on the performance of the reversible emulsion oil-based drilling fluid system shows that it has a good thermal stability and a small amount of fluid loss, and successfully reduces the damage of the traditional oil-based drilling fluids on oil well completion.     

Synergism in mixed monolayers of alkylpolyglucoside and alkylsorbitan surfactants at liquid/liquid interface

A study of nonideal behavior in the formation of mixed monolayers at the oil-water interface was performed for a nonionic-nonionic surfactant system. Mixtures containing alkylpolyglucoside and alkylsorbitan derivatives were investigated. As the oily phase, colza-rapeseed and olive oils were used. To evidence a synergetic effect in the interfacial tension reduction in the oil-water-surfactant-cosurfactant system, the model based on the regular solution theory was modified for the case of both surfactants being soluble in the water as well as in the oily phase. For determination of the condition for the synergism and the point of the maximum synergetic effect, the molar fraction in the mixed monolayer X ^s and the interaction parameter β^s were calculated, using experimental data for the interfacial tension and for the partition coefficient. A set of general equations was developed, to allow the analysis of a mixture containing a water-soluble and an oil-soluble surfactant. The equations are applied according the characteristics of studied quaternary systems. The mathematical model was tested with literature data, and the results were compared with those obtained from the phase diagram of oil-water-mixed surfactant system. The systems water-vegetable oil-alkylpolyglucoside-alkylsorbitan show a maximum synergetic effect at molar fractions between 0.85 and 0.90. The liquid-liquid interfacial tension and partition coefficient data were used to calculate the point of the maximum synergetic effect, i.e., the surfactant-cosurfactant ratio, which ensures the interfacial tension miniumum. The dramatic reduction in interfacial tension due to the presence of the surfactant mixture at the interface at the point of the synergism maximum is related to the formation of three-phase and single-phase microemulsions. The results were applied to obtain single-phase microemulsion in water-vegetable oil-alkylpolyglucoside-alkylsorbitan systems.     

A crossover multi-fluid nonrandom lattice fluid model for pure hydrocarbons and carbon dioxide near to and far from the critical region

The multi-fluid nonrandom lattice fluid model with the local composition concept is capable of describing thermodynamic properties for complex systems, but this model cannot represent the singular behavior of fluids near the critical region. In this research, the multi-fluid nonrandom lattice fluid model for pure fluids is combined with a crossover theory to obtain a crossover multi-fluid nonrandom lattice fluid model which incorporates the critical scaling laws valid asymptotically close to the critical point and reduces to the original classical multi-fluid nonrandom model far from the critical point. The crossover multi-fluid nonrandom lattice fluid model shows a great improvement in prediction of the thermodynamic properties of pure compounds near the critical region.     

Über den Einfluß des kolloichemischen Aufbaus von Trägergrundlagen auf die cutane Aufnahme eines Pharmakons. I. Entwicklung von potentiellen Transportsystemen auf der Basis von Kohlenwasserstoff als Ölkomponente

Influence of the Colloidal Structure of Vehicles on the Percutaneous Drug Absorption. I. Development of Potential Transport Systems with Hydrocarbon as Oil Component In this part the development and colloidal differentiation of some model systems is presented containing dodecane as oil, water and polyoxyethylene(7)laurylether as nonionic surfactant. In specific concentration ranges mixtures of water and surfactant give stable solutions being micellar or inverse-micellar, and two mesophases, a gel with hexagonal structures (phase M) and a region with a onedimensional lamellar lattice (phase N). Dodecane being the third component will be integrated within the unpolar regions of the structures, enlarging the diameter of the rods in the case of phase M and the thickness of lipid bilayer in the case of phase N. The formation of emulsions, creams and gels is highly depending on the presence of the hydrocarbon. Their different structures will be described, proposing a specific three-phase structure of the creams and a cubic lattice in the case of the isotropic, visco-elastic gel.     

EOS状态下基于多相流有规栅格理论的水-碳氢化合物两相体系的临界轨迹关系

Quantitative representation of complicated behavior of fluid mixtures in the critical region by any of equation-of-state theories remains as a difficults thermodynamic topics to date.In the present work,a computational efforts were made for representing various types of critical loci of binary water with hydrocarbon systems showing Type Ⅱ and Type Ⅲ phase behavior by an elementary equation of state[called multi-fluid nonrandom lattice fluid EOS(MF-NLF EOS)]based on the lattice statistical mechanical theory.The model EOS requires two molecular parameters which representing molecular size and interaction energy for a pure component and single adjustable interaction energy parameter for binary mixtures.Critical temperature and pressure data were used to obtain molecular size parameter and vapor pressure data were used to obtain interaction energy parameter.The MF-NLF EOS model adapted in the present study correlated quantitatively well the critical loci of various binary water with hydrocarbon systems.     

Microemulsion formation and detergency with oily soils: I. Phase behavior and interfacial tension

The ultimate objective of the project was to investigate the relationship between microemulsion phase behavior and detergency for oily soils. In this study, surfactant phase behavior was evaluated for hexadecane and motor oil as model oily soils. Producing microemulsions with these oils is particularly challenging because of their large hydrophobic character. To produce the desired phase behavior we included three surfactants with a wide range of hydrophilic/lipophilic character: alkyl diphenyl oxide disulfonate (highly hydrophilic), dioctyl sodium sulfosuccinate (intermediate character), and sorbitan monooleate (highly hydrophobic). This mixed surfactant was able to bridge the hydrophilic/lipophilic gap between the water and the oil phases, producing microemulsions with substantial solubilization and ultralow interfacial tension. The effects of surfactant composition, temperature, and salinity on system performance were investigated. The transition of microemulsion phases could be observed for both systems with hexadecane and motor oil. In addition, the use of surfactant mixtures containing both anionic and nonionic surfactants leads to systems that are robust with respect to temperature compared to single-surfactant systems. Under conditions corresponding to “supersolubilization”, the solubilization parameters and oil/microemulsion interfacial tensions are not substantially worse than at optimal condition for a middle-phase system, so a middle-phase microemulsion is not necessary to attain quite low interfacial tensions. A potential drawback of the formulations developed here is the fairly high salinity (e.g., 5 wt% NaCl) needed to attain optimal middle-phase systems. The correlation between interfacial tension and solubilization follows the trend predicted by the Chun-Huh equation.     

Miscibility of DMPC‐TMPC copolycarbonate/SMMA copolymer blends and their interaction energies of binary pairs involved in blends

The isothermal miscibility map and phase‐separation temperatures caused by lower critical solution temperature‐type phase behavior for blends of poly[2,2,‐propane‐bis{4‐(2‐methyl phenyl)} carbonate]‐poly[2,2,‐propane‐bis{4‐(2,6‐dimethyl phenyl)} carbonate] (DMPC‐TMPC) with poly[(styrene)‐co‐(methyl methacrylate)] (SMMA) copolymers have been determined. SMMA copolymers containing equal to or less than 37 wt% MMA formed miscible blends with DMPC‐TMPC copolycarbonates containing equal to or more than 60 wt% TMPC. The observed phase‐separation temperatures indicate that the miscibility decreases as the DMPC content in DMPC‐TMPC increases, while addition of MMA to the styrene initially increases miscibility with DMPC‐TMPC but ultimately leads to immiscibility. The binary interaction energies involved in these blends were calculated from the phase boundaries using the lattice‐fluid theory combined with the binary interaction model. The spinodal temperatures predicted from the lattice‐fluid theory using the calculated interaction energies are similar to the experimental phase‐separation temperatures. Copyright © 2004 Society of Chemical Industry     

Triton X-100-无机盐双水相体系的相平衡模型及碱性蛋白酶在该体系中的分配系数模型

研究了Triton X-100-无机盐双水相萃取体系在298 K时的相行为,建立了包含界面吸附效应的非离子表面活性剂双水相液-液平衡模型及碱性蛋白酶在其中的分配系数模型,验证了模型的可靠性和适用性.研究发现,该模型对中性范围的非离子表面活性剂双水相萃取体系的相行为及碱性蛋白酶分配平衡的模拟效果较好;非离子表面活性剂在水溶液中由于易结合离子而影响相行为,使体系更易分相;无机盐增大了碱性蛋白酶的表面疏水性,使碱性蛋白酶在疏水相中增溶.     

Synergism and Phase Behavior of Alcohol Polyoxyethylene Ether Acetate and Cationic Surfactant-Mixed Systems

Synergism in mixed micelle formation and surface tension reduction efficiency and the ternary phase behavior of anionic surfactant (alcohol polyoxyethylene ether acetate containing 10 ethylene oxide group and a fatty chain of C_16–18) with cationic surfactants (dodecyldimethylbenzyl ammonium chloride and lauryltrimethyl ammonium chloride) were investigated. Surface tension of the systems at different molar ratios was studied in detail and the interaction parameters of each system were calculated. The results show that both systems have lower values of critical micelle concentration (CMC) and γ_cmc than individual surfactants especially at equal ratio between cationic and anionic surfactants. Both systems present synergism in mixed micelle formation and surface tension reduction efficiency. The ternary phase behavior of the two systems was investigated using a polarized microscope. The micellar phase and lamellar phase were observed in both systems and the coexisting phase was only observed in the dodecyldimethylbenzyl ammonium chloride system.     

Associative polymer/latex dispersion phase diagrams II: HASE thickeners

The colloidal interactions of HASE associative polymers and latexes in the presence of surfactant are complicated and subject to a number of variables. Both bridging and depletion flocculation can occur, in addition to good particle dispersion. Dispersion phase diagrams have been developed to help visualize these interactions. The various dispersion states can have a significant effect on coating formulations and film properties. Examples of dispersion phase diagrams are presented for a model HASE anionic associative thickener and various model latexes in the presence of sodium dodecyl-sulfate and nonionic surfactants. The major variables affecting dispersion behavior are associative polymer concentration, latex particle size, latex surface hydrophobicity, electrolyte concentration, and surfactant concentration. The dispersion phase behavior of the HASE systems is compared to that of HEUR thickened systems reported previously. A significant difference is that much less bridging flocculation is observed in the HASE systems. In addition, nonionic surfactants induced depletion flocculation in the HASE systems but not in the HEUR systems.     

不同形貌纳米Fe3O4粒子磁流体的稳定性及其流度学性能

选用无规则、正八面体和六方片状形貌的纳米Fe3O4磁性颗粒作为磁流体固相材料,通过设计组装基于L–C振荡电路的磁流体稳定性测试仪,确定制备稳定磁流体的较佳表面改性活性剂和辅助表面活性剂用量。同时,对含有不同形貌磁性颗粒的磁流体在水平方向磁场以及竖直方向磁场中的磁流变学性能进行了研究。结果表明：在外加水平方向180、350、500Gs磁感应强度,磁流体的黏度、剪切应力基本不变,磁流体表现出Newtonian流体的流变学特性;在外加竖直方向360、740、1130Gs磁感应强度,磁流体表现出Bingham流体的流变学特性;对于含有正八面体形貌纳米Fe3O4颗粒的磁流体,其黏度和剪切应力随外加磁场的变化较大。     

Continuous Countercurrent Extractive Biocatalysis in Aqueous Surfactant Two‐Phase Systems

To evaluate the possibility of performing extractive biocatalysis in continuous mode, the hydrolysis of penicillin G in a micellar solution containing the nonionic surfactant Tergitol NP‐7 was chosen as model system. While the product phenylacetic acid distributes into the micellar phase, 6‐aminopenicillanic acid moves preferably into the aqueous phase. The yield in the continuous multi‐step process was higher in comparison to equivalent batch systems. Overall, the results demonstrate the suitability of aqueous surfactant two‐phase systems for continuous biocatalytic reactive extraction processes.     

Viscoelastic Behavior of Alkyl Ether Sulfate Systems Containing Nanosized Colloidal Silica

Surfactant systems incorporating wormlike micelles (WLM) are utilized in both industrial and consumer products. While the viscoelastic behavior of such systems provides for many desired end-use properties, there is often a need to further modify the rheological properties of such systems. These WLM systems behave much like polymer systems. Furthermore, incorporation of nanosized particles results in interaction of nanoparticles with the large WLM structures altering the rheological behavior. While there are a number of studies that have focused on the effect of particles on the rheological behavior in cationic surfactant systems, fewer studies have been done on systems containing anionic surfactants. In this study, relaxation behaviors in systems containing sodium alkyl ether sulfate and sodium carbonate were studied. The anionic surfactant was an alkyl ether sulfate with an average chain length of 12 carbons and one ethoxy group. WLM behavior was achieved through the addition of sodium carbonate. Ludox TMA, a nanosized colloidal silica, was employed at different concentrations in the WLM systems. Temperature was varied between 5 and 45°C. While characterization of relaxation in terms of the Maxwell model adequately described data below the threshold of ωτ ~1, the model failed to adequately describe behavior at higher frequencies. A modified expression with an additional relaxation mode adequately described relaxation throughout the frequency range studied. It was also found that zero-shear viscosities generally increased with an increase in silica concentration, and relaxation times decreased. Measurements of relaxation due to a compressive stress via ultrasonic attenuation measurements in the surfactant/particle systems are also discussed.     

Phase Transitions in Two-Dimensional Systems of Janus-like Particles on a Triangular Lattice

We studied the phase behavior of two-dimensional systems of Janus-like particles on a triangular lattice using Monte Carlo methods. The model assumes that each particle can take on one of the six orientations with respect to the lattice, and the interactions between neighboring particles were weighted depending on the degree to which their A and B halves overlap. In this work, we assumed that the AA interaction was fixed and attractive, while the AB and BB interactions varied. We demonstrated that the phase behavior of the systems considered strongly depended on the magnitude of the interaction energies between the AB and BB halves. Here, we considered systems with non-repulsive interactions only and determined phase diagrams for several systems. We demonstrated that the phase diagram topology depends on the temperature at which the close-packed systems undergo the orientational order–disorder transition.     

Phase stability of ternary blends

The phase behavior of ternary blends of tetramethyl polycarbonate (TMPC), polycarbonate (PC), and styrenic polymers has been examined by experiment and analyzed in terms of thermodynamic theories. The phase boundaries were predicted using both the modified Flory-Huggins theory and the lattice fluid theory. The boundaries predicted using the lattice fluid theory agree best with the experimental results. The experimental phase behavior of ternary blends was compared with binary blends having exactly the same chemical components and compositions except that the TMPC and PC units were present in the form of a copolycarbonate in the binary. The miscible region of these ternary blends is much narrower than that of the corresponding binary blends, even though the entropic and energetic terms of such ternary blends are more favorable than those of the binary blends. It is shown that a negative value of noncombinatorial free energy in multicomponent systems is not a sufficient condition for miscibility, because of asymmetries of mer-mer interactions. A comparison of the stability conditions for these binary and ternary blends shows that increasing the degrees of freedom tends to destabilize the mixture.     

Synergisms in Binary Mixtures of Anionic and pH‐Insensitive Zwitterionic Surfactants and Their Precipitation Behavior with Calcium Ions

This work aims to investigate synergy in anionic and zwitterionic surfactant mixtures, as they result in better interfacial properties and micellization behavior. Various mixtures of the pH‐insensitive zwitterionic surfactant 3‐(decyldimethylammonio) propanesulfonate (Zwittergent 3–10) and sodium dodecylsulfate (SDS) were prepared in aqueous solution at a range of pH values between 2 and 13. The thermodynamic parameters during mixed surfactant adsorption at the air/water interface are obtained and the results show the mixed surfactant systems having superior properties to the constituent surfactants. Experimentally, the mixed surfactant solutions clearly improve the surface activities by lowering the critical micelle concentration (CMC) and lowering the surface tension at the air/water interface. The synergisms are investigated through the interaction parameters estimated from regular solution theory that is used to quantitatively describe the nonideality of surfactant mixtures. High negative interaction parameters are obtained from these surfactant mixtures. Experimental precipitation phase boundaries of SDS in the presence of CaCl₂ were also investigated in mixtures containing pH‐insensitive zwitterionic surfactant at different pH levels from 2 to 13 and SDS mole fractions of 0.25, 0.50, 0.75, and 1.00. Changes in the precipitation phase boundaries are due to the changes in the speciation or activities of the major components both below and above the CMC. As a result, the precipitation phase boundaries are pH dependent. In addition, mixed micellization and counterion binding to the micelle also change the precipitation phase boundary above the CMC. The activity‐based solubility product of calcium dodecylsulfate is also determined from the precipitation phase boundaries below the CMC. X‐ray diffraction patterns and SEM images confirm that only calcium dodecylsulfate precipitates in the soap scum for all pH and surfactant compositions studied.     

Phase behaviors of binary polymer solutions: The extended lattice fluid model

The generalized lattice–fluid (GLF) model is extended to predict phase behaviors of polymer/solvent systems. The GLF model gives some difficulties in describing liquid–liquid equilibria (LLE) of binary polymer solution systems due to general assumptions on its derivation. An extended lattice–fluid (ELF) model is proposed by introducing a new universal constant (C₀) and a model parameter (κ₁₁). The proposed model is then compared with experimental data for polymer/solvent systems and polymer1/polymer2 systems, which exhibit lower critical solution temperature (LCST) behaviors. Theoretical predictions and experimental results are in good agreement. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 1143–1150, 1998