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

Experimental The pyrene was purchased from Sigma Co., and the other chemicals were of A. R. grade. Water was deionized and distilled twice before use. The microemulsions of required compositions were prepared in the following way. The stock microemulsions were made without water at first, corresponding to the A point (10wt% octane, 63wt% n-butanol, 27wt% CTAB) in the phase diagram of Figure 1 and then a series of microemulsions were made along AW dilution line with adding water. Calcu…     

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 restult 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.     

Phase separation of ploy(ethylene glycol) + n-butanol mixture induced by supercritical CO_2

The phase behavior of supercritical (SC) CO2 PEG 1000 (PEG with average molecular weight of 1000 g/mol) n-butanol system was studied. It was demonstrated that SC CO2 could induce phase separation of PEG 1000 n-butanol system under suitable conditions. This hints that SC CO2 has potential applications in the separation of mixtures of PEG organic compound.     

The Catalysis of Sodium Dodecyl Sulfate／1-Pentanol／Water W／O Microemulsion on the Photoisomerization of trans-Stilbene

The photoisomerization of trans-stilbene was studied in the water in oil (W/O) microemulsion formed by SDS (sodium dodeeyl sulfate), n-C5H11OH (1-pentanol) and H2O. The experimental results show that after 2-minute UV-irradiation, the yield of cis-stilbene is higher in W/O mieroemulsion than in homogeneous solvent-n-C5H11OH.     

Hydrolysis of Cephanone in SDS／n－C5H11OH／H2O System

The hydrolysis of cephanone in SDS micelle and SDS/n-C5H11-OH/H2O O/W microemulsion was studied through Uv-vis ab-sorption spectroscopy. The change of pH value in the hydrolysis of cephanone was determined. The result shows that pH value decreases in the process of the hydrolysis, and that the SDS ml-celle and SDS/n-C5H11OH/H2O O/W microemulsion accelerate the hydrolysis of cephanone compared with water.     

Acceleration of disproportionation reactions of aryl alcohols in water medium by CO2

Compressed CO2 could promote the disproportionation reactions of aryl alcohols in water medium significantly.The control experiments indicated that the effect of CO2 on the properties of the reactant/water emulsions was the main reason for the acceleration of the reactions rate.     

Determination of water states and the structural parameters of W/O microemulsions

The states of water in sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/isooctane/water reverse(W/O) microemulsions system have been investigated by using Fourier transform infrared spectroscopy(FT-IR) technique. The broad peak obtained for hydroxy(O-H) of water has been resolved by least square curve-fitting. It has been observed that the water solubilized in microemul-sion droplets has four states, i.e. bound water with sulfo-group, free water, bound water with sodium counterion in the water pool of microemulsion droplets and a small amount of trapped water in the palisade layer of microemulsion droplets. The following have also been determined: the aggregation number (n), the radius of the water pool in the microemulsions(rw), the thickness of the bound water with sulfo-group(d1), the thickness of the bound water with sodium counterion(d2), the total thickness of the bound water (d) and the effective area of head groups of AOT(AAOT).     

Studies on the intestinal absorption of the alkaloids in the Gancaofuzi decoction in a Caco-2 cell culture system by UPLC–MS/MS analysis

In this study, the Caco-2 cell monolayer model was used to research the characteristic absorption and efflux of five diterpenoid alkaloids in Gancaofuzi decoction. An ultra performance liquid chromatography coupled with tandem mass spectrometry(UPLC–MS/MS) method was developed for the determination of the simulated intestinal transport of five diterpenoid alkaloids with reserpine as internal standard. The use of the apparent permeability coefficient(Papp) and efflux rate(Er) was instituted to evaluate the intestinal absorption of the alkaloids. Transport of the five alkaloids in Caco-2cell monolayer model was observed to better understand whether the intestinal absorption of alkaloids was influenced by the compatibility of four herbs in Gancaofuzi decoction. The results show that the Papp values of the five diterpenoid alkaloids were all more than 1 * 10~(-6)cm/s, confirming that the processes of permeability were valid. The flux of the alkaloids was time-dependent, and the intestinal absorption mechanism of the five alkaloids was mainly based on passive transport. The compatibility of Heishunpian, Baizhu, Guizhi and Gancao can reduce the intestinal absorption of alkaloids, especially the most toxic hypaconitine, and the attenuated effect of mixed herbal water extracts was better than that of different herbs' water extracts combination. The results prove that compatibility of four herbs in Gancaofuzi decoction is rational.     

Electrochemical Oxidation of L-Cystenine in SDS／BA／H2O Microemulsion

The electrochemical oxidation of L-cysteine in an SDS/BA/H2O microemulsion system was studied with the methods of ultramicroelectrode cyclic voltammetry and AC impedance. The catalytic efficiency of the microemulsion on the electrochemical oxidation increases with the increase of BA or SDS content, but decreases with the increase of the water content because of the effects of BA, SDS and water on the solubilization of Lcysteine in the microemulsion. Furthermore, the catalytic efficiency of the bicontinuous structure is greater than that of an O/W microemulsion system. The results derived from both the rate constant k^0 and Gibbs free energy △G^≠ accord with those from the catalytic efficiency.     

In situ Observation of the Photochromism in the Langmuir Monolayer of a Non—typical Amphiphilic Spiropyran Derivative at the Air／Water Interface

In situ photochromic process in the monolayer of aphotochromic spiropyran derivative without long alkyl chain,was investigated.The photochromism at the air/water interface under differnet surface pressures was studied by surface pressure-area isotherms,surface pressure-time curves,area-time curves and Brewster angle microscopy.Both forms of the compound were found to form monolayers at the air/water interface althouhg it does not have long alkyl chain.A large area expansion in the monolayer corresponding to a zreo^th order reaction was found at the initial stage of the UV light irradiation.A series of dynamic investigations revealed that at high pressure after phase transition in the monolayer,the surface pressure changes greatly umder alternative irradiation of UV and visible light.An obvious morphological change accompanying with the photochromism was observed in situ.     

双子表面活性剂Dynol-604溶液的动态表面张力研究

通过测定双子表面活性剂Dynol-604的动态表面张力(DST),研究了温度和浓度等对其DST的影响,详细表征了DST随时间的变化过程,计算了动态表面张力的各种参数(t_i,t^*,t_m,R_1/2).结果表明,其表面张力降低迅速,γ_m值也很低.探讨了上述参数的物理意义和变化规律.     

添加剂对双子表面活性剂DYNOL－604浊点的影响

对双子表面活性剂DYNOL－604的浊点开展研究,考察了添加剂对其浊点的影响 。离子表面活性剂的加入,使其浊点升高,而加入醇时出现了一种双浊点的现象, 我们称之为“下限浊点”和“上限浊点”。即温度低于“下限浊点”和高于“上限 浊点”,体系由浑浊变为澄清。采用NMR手段测定“上限浊点”以上温度体系的自 扩散系数,证明为双连续微乳液结构,并从R比值理论进行分析。     

Formation of water-in-CO(2) microemulsions with non-fluorous surfactant Ls-54 and solubilization of biomacromolecules

The solubility of Ls-54 surfactant in supercritical CO(2) was determined. It was found that the surfactant was highly soluble in SC CO(2) and the water-in-CO(2) microemulsions could be formed, despite it being a non-fluorous and non-siloxane nonionic surfactant. The main reasons for the high solubility and formation of the microemulsions may be that the surfactant has four CO(2)-philic groups (propylene oxide) and five hydrophilic groups (ethylene oxide) and its molecular weight are relatively low. The results of this work provide useful information for designing CO(2)-soluble non-fluorous and non-siloxane surfactants. The phase behavior of the CO(2)/Ls-54/H(2)O system, solvatochromic probe study, and the UV spectrum of lysozyme proved the existence of water domains in the SC CO(2) microemulsions. The method of synchrotron radiation small-angle X-ray scattering was used to obtain the structural information on the Ls-54 based water-in-CO(2) reverse micelles. By using the Guinier plot (ln I(q) versus q (2)) on the data sets in a defined small q range (0.022-0.040 A(-1)), the radii of the reverse micelles were obtained at different pressures and molar ratio of water to surfactant, W(0), which were in the range of 20.4-25.2 A.     

Carbon dioxide-in-water microemulsions

Liquid and supercritical carbon dioxide swell potassium carboxylate perfluoropolyether (PFPE-K) cylindrical micelles in water to produce novel CO(2)-in-water (C/W) microemulsions. The swelling elongates the micelles significantly from 20 to 80 nm as the molar ratio of CO(2) in the micelles to surfactant (R(CO2)) reaches approximately 8. As the micelles swell to form microemulsions, the solubility of pyrene increases by a factor of ca. 10. Fluorescence spectra suggest that pyrene resides primarily in the low-polarity micelle core rather than in the palisade region. The results illustrate the ability of C/W microemulsions to solubilize both lipophilic and fluorophilic substances simultaneously.     

Phase behavior of CO2-expanded fluorinated microemulsions

The formation of CO2-expanded, fluorinated reverse microemulsions is demonstrated for the system of perfluoropolyether (PFPE) surfactant (ClPFPE-NH4, MW = 632) and PFPE oil (PFPE, MW = 580). The phase behavior of this system is examined as a function of temperature (25-45 degrees C), pressure, CO2 concentration, and water to surfactant molar ratios (W0 = 10 and 20). Visual observations of one-phase behavior consistent with reverse microemulsion formation are further supported by spectroscopic measurements that establish the existence of a bulk water environment within the aqueous core. Microemulsion formation is not observed in the absence of CO2 for this PFPE surfactant/PFPE oil system, and a CO2 content greater than 70 mol % is required to induce microemulsion formation. Over the range of water loadings and temperatures investigated, the lowest cloud point pressure is observed at 46 bar (5 wt % ClPFPE-NH4 in PFPE oil, W0 = 20, xCO2 = 0.7, T = 25 degrees C). In the regions where one-phase behavior is observed, the cloud point pressures increase with temperature, water loadings, and CO2 content. The driving forces of microemulsion formation in the CO2-expanded fluorinated solvent are discussed relative to traditional reverse microemulsions and CO2-continuous microemulsions.     

Surfactant-mixing effects on the interfacial tension and the microemulsion formation in water/supercritical CO2 system

The effects of surfactant mixing on interfacial tension and on microemulsion formation were examined for systems of air/water and water/supercritical CO2 (scCO2) interfaces and for water/scCO2 microemulsions. A fluorinated surfactant, sodium bis(1H,1H,2H,2H-heptadecafluorodecyl)-2-sulfosuccinate (8FS(EO)2), was mixed with the three hydrocarbon surfactants, Pluronic L31, Tergitol TMN-6, and decyltrimethylammonium chloride (DeTAC), at equimolar ratio. For all the cases, the interfacial tension was significantly lowered by the mixing. The positive synergistic effect suggests that the mixed surfactants tend to pack more closely on the interface than the pure constituents. It was found, however, that the microemulsion formation in scCO2 was never facilitated by the mixing, except for the case of TMN-6. This is probably due to the segregation of the surfactants into hydrocarbon-rich and fluorocarbon-rich phases on the microemulsion surface.     

Studies on the micropolarities of bmimBF4/TX-100/toluene ionic liquid microemulsions and their behaviors characterized by UV-visible spectroscopy

Ionic liquids (ILs), 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4), were substituted for polar water and formed nonaqueous microemulsions with toluene by the aid of nonionic surfactant TX-100. The phase behavior of the ternary system was investigated, and microregions of bmimBF4-in-toluene (IL/O), bicontinuous, and toluene-in-bmimBF4 (O/IL) were identified by traditional electrical conductivity measurements. Dynamic light scattering (DLS) revealed the formation of the IL microemulsions. The micropolarities of the IL/O microemulsions were investigated by the UV-vis spectroscopy using the methyl orange (MO) and methylene blue (MB) as absorption probes. The results indicated that the polarity of the IL/O microemulsion increased only before the IL pools were formed, whereas a relatively fixed polar microenvironment was obtained in the IL pools of the microemulsions. Moreover, UV-vis spectroscopy has also shown that ionic salt compounds such as Ni(NO3)2, CoCl2, CuCl2, and biochemical reagent riboflavin could be solubilized into the IL/O microemulsion droplets, indicating that the IL/O microemulsions have potential application in the production of metallic or semiconductor nanomaterials, and in biological extractions or as solvents for enzymatic reactions. The IL/O microemulsions may have some expected effects due to the unique features of ILs and microemulsions.     

New phosphate fluorosurfactants for carbon dioxide

Anionic phosphate fluorosurfactants were shown to self-assemble into water-in-carbon dioxide microemulsions. The surfactants, having either two fluorinated chains or one fluorinated chain and one hydrocarbon chain, facilitated significant water uptake in CO2. Small angle neutron scattering (SANS) measurements of surfactant/water/CO2 solutions confirmed the presence of nanometer-scale aggregates, indicative of microemulsion formation.     

Phase Behavior of Bicontinuous and Water/Diesel Fuel Microemulsions Using Nonionic Surfactants Combined with Hydrophilic Alcohol Ethoxylates

Bicontinuous and water-in-diesel microemulsions were formulated using single nonionic alkyl poly glycol ethers combined with hydrophilic alcohol ethoxylates. The phase behavior at temperatures ranging from 0°C to 50°C was investigated. Visual inspection as well as cross-polarizers were used to detect anisotropy. The fish phase diagrams were determined. The presence of the hydrophilic alcohol ethoxylates was necessary to initiate both types of microemulsions. Increasing the hydrophobic chain length of the surfactant led to a wider range of temperature stability at lower surfactant concentration. Meanwhile, increasing the ethylene oxide units in the headgroup by two units led to a phase diagram that is dominated by lyotropic liquid crystal. The formulated water in diesel microemulsions were tested experimentally in a 4-cylinder diesel engine. From this it is observed that the emissions of NO_x, soot, and CO₂ were reduced substantially compared to neat diesel, while for the CO the reduction occurs just at low load.      

Role of solubilized water in the reverse ionic liquid microemulsion of 1-butyl-3-methylimidazolium tetrafluoroborate/TX-100/benzene

The ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4) can form nonaqueous microemulsions with benzene by the aid of nonionic surfactant TX-100. The effect of water on ionic liquid-in-oil (IL/O) microemulsions was studied, and it was shown that the addition of small amount of water to the IL microemulsion contributed to the stability of microemulsion and thus increased the amount of solubilized bmimBF4 in the microemulsion. The conductivity measurements also showed that the attractive interactions between IL microdroplets were weakened, that is, the IL/O microemulsion becomes more stable in the present of some water. Fourier transform IR was carried out to analyze the states of the added water, and the result showed that these water molecules mainly behaved as bound water and trapped water, indicating that the water molecules are located in the palisade layers of the IL/O microemulsion. Furthermore, 1H NMR and 19F NMR spectra suggested that the added water molecules built the hydrogen binding network of imidazolium cations and H2O, BF4- anion and H2O, and at the same time the electronegative oxygen atoms of the oxyethylene units of TX-100 and water in the palisade layers, which made the palisade layers more firm and thus increased the stability of the microemulsion. The study can help in further understanding the formation mechanism of microemulsions. In addition, the characteristic solubilization behavior of the added water can provide an aqueous interface film for hydrolysis reactions and therefore may be used as an ideal medium to prepare porous or hollow nanomaterials.