Study on the Phase Behavior of Supercritical CO2/Dynol-604/Water System and Solubilization of Methyl Orange in the Microemulsions

It was found that Dynol-604, a non-fluorous and no silicon-containing nonionic surfactant, was soluble in supercritical (SC) CO2. The phase behavior of SC CO2/Dynol-604/water system was studied. The results showed that one-phase water-in-CO2 microemulsions could be formed. The solubilization of methyl orange in the microemulsions proved further the existence of water domain in the microemulsions.

Physicochemical Properties of Rhamnolipid Biosurfactant from <i>Pseudomonas aeruginosa</i>PA1 to Applications in Microemulsions

Interfacial properties rhamnolipids from an extract produced by a strain of Pseudomonas aeruginosa were analyzed in this study. The extract of rhamnolipid was characterized by surface tension in different conditions;interfacial tension with different hydrocarbons;critical micelle concentration under different pH and temperatures;particle size and emulsification capacity using laser light profiling. It was observed that the rhamnolipids extract are sensitive to variations in pH, thermostable and function as good emulsificant for emulsification of methyl methacrylate. The emulsion stability order in function of the oil phase was methyl methacrylate > emulsions of castor oil > emulsion n-heptane > emulsion toluene > emulsion hexadecane > octane emulsion. The data presented show that rhamnolipid extracts may be used to formulate stable emulsions of methyl methacrylate. This process can be used to do nano/microsphere of polymethyl methacrylate.

Rheological characteristics of drug-loaded microemulsions and their printability in three dimensional printing systems

Rheological properties of microemulsions(MEs) and their printability in three dimensional printing(3DP) systems were investigated.A series of MEs with different contents of oil phase were prepared using sonication method with ibuprofen as model drug and soybean lecithin as emulfier.Stationary and transient rheological properties of MEs were investigated by ARES-SRF using concentric cylinders measuring systems.3DP systems with piezoelectric drop-on-demand print heads were employed to test the printability of the MEs.Results demonstrate that the apparent viscosity and dynamic linear viscoelastic regions of the MEs are the most important parameters for continuous and stable printing of MEs by 3DP.The incorporation of drug in the MEs has little influence on the MEs' stationary rheological behaviors and dynamic viscoelasticity,but the concentration of oil phase has a strong influence on them.The rheological property of binder liquids has a close relationship with their printability in 3DP system.

A study of the mechanism of enhancing oil recovery using supercritical carbon dioxide microemulsions

Supercritical carbon dioxide （scCO2） microemulsion was formed by supercritical CO2, H20, sodium bis（2-ethylhexyl） sulfosuccinate （AOT, surfactant） and C2HsOH （co-surfactant） under pressures higher than 8 MPa at 45 ℃. The fundamental characteristics of the scCO2 microemulsion and the minimum miscibility pressure （MMP） with Daqing oil were investigated with a high-pressure falling sphere viscometer, a high-pressure interfacial tension meter, a PVT cell and a slim tube test. The mechanism of the scCO2 microemulsion for enhancing oil recovery is discussed. The results showed that the viscosity and density of the scCO2 microemulsion were higher than those of the scCO2 fluid at the same pressure and temperature. The results of interfacial tension and slim tube tests indicated that the MMP of the scCO2 microemulsion and crude oil was lower than that of the scCO2 and crude oil at 45 ℃. It is the combined action of viscosity, density and MMP which made the oil recovery efficiency of the scCO2 microemulsion higher than that of the scCO2 fluid.

Water solubility enhancements of PAHs by sodium castor oil sulfonate microemulsions

Water solubility enhancements of naphthalene(Naph), phenantherene(Phen) and pyrene(Py) in sodium castor oil sulfonate(SCOS) microemulsions were evaluated. The apparent solubilities of PAHs are linearly proportional to the concentrations of SCOS microemulsion, and the enhancement extent by SCOS solutions is greater than that by ordinary surfactants on the basis of weight solubilization ratio(WSR). The log K em values of Naph, Phen, and Py are 3 13, 4 44 and 5 01 respectively, which are about the same as the log K ow values. At 5000 mg/L of SCOS conccentration, the apparent solubilities are 8 80, 121, and 674 times as the intrinsic solubilities for Naph, Phen, and Py. The effects of inorganic ions and temperature on the solubilization of solutes are also investigated. The solubilization is improved with a moderate addition of Ca 2+ , Na +, NH + 4 and the mixture of Na +, K +, Ca 2+ , Mg 2+ and NH + 4. WSR values are enhanced by 22 0% for Naph, 23 4% for Phen, and 24 6% for Py with temperature increasing by 5℃. The results indicated that SCOS microemulsions improve the performance of the surfactant enhanced remediation(SER) of soil, by increasing solubilities of organic pollutants and reducing the level of surfactant pollution and remediation expenses.

Kinetics of the Esterification Reaction Catalyzed by Lipase in W/O Microemulsions of Alkyl Polyglucoside

A novel kinetic mechanism of esterification reaction of 1-hexanoic acid with 1-butanol, catalyzed by lipase, was studied in water-in-oil microemulsions. The microemulsions were formed by alkyl polyglucoside C10G1.54/1-butanol / cyclohexane/phosphate buffer solution. The result shows that when the ratio of mol concentration of 1-butanol to 1-hexanoic acid is about 3.0, the initial rate V0 get the maximum values. This phenomenon was explained by the modified fishlike phase diagrams.

Studies on Phase Behavior of Alkyl Polyglucoside Based on Microemulsions with Modified Fishlike Phase Diagram

The three-phase behavior in the quaternary system of an alkyl (C8/10- or C12/14-) polyglucoside / 1-butanol / n-octane / water has been studied at 40 ℃ with the modified fishlike phase diagram, which is presented by us for the first time. The mass fraction of 1-butanol in the hydrophile-lipophile balanced interfacial layer, AS, the coordinates of the start point B and the end point E of the phase diagram, and the solubilities of alkyl polyglucoside and 1-butanol in n-octane phase were calculated. The solubilization of the microemulsion was also discussed.

Uniform Rice-like CdS Particles Prepared from Water-in-oil Microemulsions

Uniform rice-like CdS particles were synthesized in cyclohexane/Triton X-100/n-pentanol/water quaternary microemulsions. The as-prepared samples were characterized by X-ray diffraction, transmission electron microscopy, and electron diffraction. The results indicate that the size and the shape of the rice-like CdS particles can be influenced by the molar ratio of water to the surfactant（w value） and the reactant concentrations.

Preparation of Ultrafine γ-Al_2O_3 Particles in Non-ionic Water in Oil Microemulsions

Ultrafine γ-A12O3 particles are synthesized in Triton X- 10 0/n - hexanol/cycloh exan e/wat er water in o if(w/o )Inicroemulsion by mixing two separately prepared microemulsions containing Al(NO)3 and (Wb)ZCO, respectively.The ultrafine Al2O3 particles are characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD)and their size and distribution are measured. The effects of water, surfactallt and reactant concentrations on the particlesize and distribution are studied. The results show that the particle size and distribution can be changed by varying thepreparation conditions, and the size of the microemulsion droplets has a controlling effect on the size of the pafticles. A. possible mechanism of ultrafine particles (UFPs) prepared by microemulsions is proposed.

Phase Structures of Microemulsions Determined by the Steady-State Fluorescence Method

The steady-state fluorescence method has been tentatively used to determine the phase structures of microemulsion systems consisting of cetyltrimethylammonium bromide (CTAB), n-butanol (n-C4H9OH), octane (n-C8H18), and water. The excimer/monomer intensity ratio (I-e/I-m) of pyrene has demonstrated that the various structures in the microemulsion phase region can be distinguished. The results are consistent with electrical conductivity data already reported.

Monitor of Polymerization of Inverse Microemulsions Containing Methyl Methacrylate and Acrylic Acid

The polymerization of the inverse microemulsions composed of methyl methacrylate,acrylic acid, sodium dodecyl sulfate and water was monitored by refractometer, conductometer and time-resolved light scattering device. The results showed that refractive index, conductivity or intensity distribution of scattered light changed along with polymerization, and different processes of polymerization could be identified.

Studies on the Phase Properties of Winsor Ⅰ-Ⅲ Type Microemulsions with Dielectric Relaxation Spectroscopy

The dielectric relaxation spectroscopy （DRS） of Winsor I -Ⅲ microemulsions for nonionic surfactant octyl polyglucoside CsG1.46/1-butanol/cyclohexanedwater system was studied. The experiment shows that the permittivity decreases with the increase in the frequency and clear dielectric relaxation phenomena were observed. Permittivity obviously decreases with the change of the microstructure of the microemulsion, W/O, B.C. and O/W can be distinguished by the permittivity.

Formation and Solubilization Property of Water-in-Oil Microemulsions of Alkyl Glucosides

The dependence of solubilization properties on the alkyl chain length of alkyl glucosides (AG) in AG/isooctane/ n-butanol/water system was investigated. The stable Winsor II system consisting of a water-in-oil (w/o) microemulsion phase and an aqueous phase was formed in AG/isooctane/n-butanol/water system. The apparent critical micelle concentration of AG reverse micelles in organic phases was markedly dependent upon the alkyl chain length of AG. The limiting amount of solubilized water increased with an increase in the alkyl chain length of AG. The solubilization capacity of methyl orange (MO) was superior to that of methylene blue (MB), and the solubilization capacities of MO and MB tended to increase with increasing the alkyl chain length of AG. Reverse micelles of dodecyl glucoside (AG12) exhibited the significant solubilization capacities of cytochrome c and lysozyme, while ribonuclease A was not solubilized by AG12 reverse micelles.

Controlled Synthesis of CuO Nanoparticles by TritonX-100-based Microemulsions

CuO nanoparticles were synthesized by using microreactors made of Triton X-100/n-hextnol/cyclohexane/water W/O microemulsion system. Basic synthesis parameters were determined. The results of thermo gravimetric/differential thermal analysis（TG/DTA） of the precursor products indicated that the proper calcination temperature was about 500 ℃. The nanoparticles were characterized by X-ray diffraction（XRD）, transmission electron microscopy（TEM） and UV-visible spectra. It was indicated that the grain size was highly dependent on the ratio of water to surfactant（R）. With the R value increasing, the particles size became larger.

In situ monitoring of the structural change of microemulsions in simulated gastrointestinal conditions by SAXS and FRET

Microemulsions are promising drug delivery systems for the oral administration of poorly watersoluble drugs. However, the evolution of microemulsions in the gastrointestinal tract is still poorly characterized,especially the structural change of microemulsions under the effect of lipase and mucus. To better understand the fate of microemulsions in the gastrointestinal tract, we applied small-angle X-ray scattering(SAXS) and fluorescence resonance energy transfer(FRET) to monitor the structural change of microemulsions under the effect of lipolysis and mucus. First, the effect of lipolysis on microemulsions was studied by SAXS, which found the generation of liquid crystalline phases. Meanwhile, FRET spectra indicated micelles with smaller particle sizes were generated during lipolysis, which could be affected by CaCl_2, bile salts and lecithin. Then, the effect of mucus on the structural change of lipolysed microemulsions was studied. The results of SAXS and FRET indicated that the liquid crystalline phases disappeared, and more micelles were generated. In summary, we studied the structural change of microemulsions in simulated gastrointestinal conditions by SAXS and FRET, and successfully monitored the appearance and disappearance of the liquid crystalline phases and micelles.

Studies on Middle-Phase Microemulsions of Green Surfactant n-Dodecyl Polyglucoside C_(12)G_(1.46)

The three-phase behavior in the quaternary system of n-dodecyl polyglucosideC_(12)G_(1.46)/1-butanol/cyclohexane/water has been studied at 40℃ in terms of the variables γ andδ. Increasing δ at constant γ causes a phase inversion from an oil-in-water microemulsion incontact with excess oil (winsor Ⅰ or 2) to a water-in-oil microemulsion in contact with excesswater (winsor Ⅱ or 2) via a middle-phase microemulsion in contact with excess oil and water (winsorⅢ or 3). By taking into account the different solubilities of alkyl pdyglucoside and 1-butanol inthe oil phase, the composition of the hydrophile-lipophile balanced interfacial film in the middleof the three-phase body can be calculated. The effects of different oils and aqueous media on thephase behavior and on the composition of the interfacial film and the efficiency for alkyipolyglucoside to make equal weights of water and oil to a single phase were investigated. It wasfound that the oil molecules with small molecular volumes can improve the solubilizing efficiency ofthe surfactant to form single-phase microemulsion. In inorganic salt (NaCl) and acid (HCl)solutions, less 1-butanol is needed than that in alkali (NaOH) solution to form middle-phasemicroemulsion.

Middle-phase microemulsions of green surfactant alkyl polyglucosides

The microemulsion behavior in the quaternary system alkyl polyglucoside (C8G1.46 , C10G1.54)/1-butanol/cyclohexane/water has been studied at 40℃ with the alcohol concentration scanning and the fishlike phase diagram methods. Increasing d at a constant causes a phase inversion from an oil-in-water microemulsion in contact with excess oil (Winsor I or 2 ) to a wa-ter-in-oil microemulsion in contact with excess water (Winsor II or 2) via a middle-phase microe-mulsion in contact with excess oil and water (Winsor III or 3). By using the simple mass balance equation and the HLB plane equation, the mass fraction of 1-butanol in the interfacial layer, S s2, the monomeric solubilities of APG and 1-butanol, S1 and S2, in the oil phase, and the mass frac-tions of APG and 1-butanol in the interfacial layer (C1 and C2 ) have been calculated, respectively. The effects of different alcohols, aqueous media and oils on the phase behavior and the composi-tion of the interfacial layer are also investigated. It is found that the alcohols with longer hydrocar-bon chain, oil molecules with smaller molecular volume and the addition of inorganic salt can in-crease the solubilization of the microemulsions .

FT-IR studies on the conformation and effective head-group area of AOT molecules in W/O microemulsions

Using Fourier transform infrared(FT-IR) spectroscopy technique, the carbonyl stretching vibration bands of AOT in sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/isooctane/water reverse (W/O) microemulsions system have been investigated by least square curve fitting. The results indicate that an asymmetric adsorbed peak of carbonyl stretching vibration of AOT molecule is situated in (1739 ± 1) and (1725 ± 2) cm-1. The two peaks correspond to different carbonyls in gauche conformation and trans conformation of AOT molecules, respectively. With different water contents (W0), the variations of peak intensity ratio (/= l1739/l1725) reflect the change of the ratio for the two conformation populations and the variations of the effective head-group area of AOT molecule have relations to the ratio of two conformation populations.

Formation and Characteristics of Middle-phase Microemulsions——Effect of Synergism of Surfactants, Alcohol and Oil

Microemulsions can be divided into simple-phase microemulsions and multi-phasemicroemulsions. The former is a system with only an independent phase while the lat-ter corresponds to a multi-phase system comprising the microemulsions and another(oil or water) or two (oil and water) phases. When the microemulsions are in the mid-

Polymerization kinetics of acrylamide in micelles and microemulsions

Catalysis of solution reactions by surfactant micelles has been investigated for morethan three decades following the pioneering work by Duynstee and Grunwald in 1959.Micelles have been used as mimic enzymic catalysts, and biocatalysis in micellar systemshas attracted much attention during recent years.