电解质和乙醇对DNA与Gemini表面活性剂相互作用的影响

应用荧光探针和zeta电位方法研究了电解质NaBr、NaCl、KCl和有机溶剂乙醇对DNA与Gemini表面活性剂相互作用的影响. DNA诱导的表面活性剂类胶束在较低浓度即可生成, 这一浓度称为临界聚集浓度(CAC). Gemini表面活性剂比具有相同烷烃链长的单体表面活性剂更易聚集, 对应的CAC较低. 实验结果表明, 盐(NaBr)浓度对DNA/表面活性剂体系的CAC影响不大, 阴、阳离子的种类则对该体系有不同程度的影响. 阴离子(Br-、Cl-)对体系的CAC有显著的影响, 但阳离子(Na+、K+)的差异对CAC影响不大. 极性溶剂乙醇对DNA与表面活性剂相互作用的影响比较复杂. 乙醇浓度较低时有利于表面活性剂的聚集, 使得CAC减小; 而浓度较高时, 则不利于表面活性剂聚集,从而使CAC变大. 乙醇可显著改变DNA/表面活性剂复合物的zeta电位.     

Salt effect on the complex formation between polyelectrolyte and oppositely charged surfactant in aqueous solution

The complex formation between sodium carboxymethylcellulose (NaCMC) and dodecyltrimethylammonium bromide (DTAB) at various sodium bromide concentrations (C(NaBr)) has been studied by microcalorimetry, turbidimetric titration, steady-state fluorescence measurements, and the fluorescence polarization technique. The addition of salt is found to influence the formation of NaCMC/DTAB complexes markedly. At C(NaBr) = 0.00, 0.01, 0.02, 0.10, and 0.20 M, DTAB monomers form micelle-like aggregates on NaCMC chains to form NaCMC/DTAB complexes above the critical surfactant concentration (C1). At C(NaBr) = 0.23 M, DTAB molecules first form micelles above a 2.46 mM DTAB concentration prompted by the added salt, and then, above C1 = 4.40 mM, these micelles can aggregate with NaCMC chains to form NaCMC/DTAB complexes. However, at C(NaBr) = 0.25 M, there is no NaCMC/DTAB complex formation because of the complete salt screening of the electrostatic attraction between DTAB micelles and NaCMC chains. It is also surprisingly found that the addition of NaBr can bring out a decrease in C1 at C(NaBr) < 0.20 M. Moreover, the addition of NaBr to a mixture of 0.01 g/L NaCMC and 3.6 mM DTAB can directly induce the formation of NaCMC/DTAB complexes. This salt-enhancing effect on the complex formation is explained as the result of competition between the screening of interaction of polyelectrolyte with surfactant and the increasing of polyelectrolyte/surfactant interaction owing to the growth of micelles by added salt. When the increasing of polyelectrolyte/surfactant interaction exceeds the screening of interaction, the complex formation can be enhanced.     

Complexation of DNA with cationic gemini surfactant in aqueous solution

Interactions between DNA and the cationic gemini surfactant trimethylene-1,3-bis(dodecyldimethylammonium bromide) (12-3-12) in aqueous solution have been investigated by UV-vis transmittance, zeta potential, and fluorescence emission spectrum. Complexes of DNA and gemini surfactant are observed in which the negative charges of DNA are neutralized by cationic surfactants effectively. The DNA-induced micelle-like structure of the surfactant due to the electrostatic and hydrophobic interactions is determined by the fluorescence spectrum of pyrene. It is found that the critical aggregation concentration (CAC) for DNA/12-3-12 complexes depends little on the addition of sodium bromide (NaBr) because of the counterbalance salt effect. However, at high surfactant concentration, NaBr facilitates the formation of larger DNA/surfactant aggregates. Displacement of ethidium bromide (EB) by surfactant evidently illustrates the strong cooperative binding between surfactant and DNA. In contrast to that in the absence of surfactant, the added NaBr at high surfactant concentration influences not only the binding of surfactant with DNA, but also the stability of DNA/EB complex.     

Gemini表面活性剂(12-6-12)和DNA的相互作用

应用紫外光谱、荧光探针、zeta 电位、动态光散射和凝胶电泳等方法探讨了阳离子gemini 表面活性剂C₁₂H₂₅N⁺(CH₃)₂―(CH₂)₆―(CH₃)₂N⁺C₁₂H₂₅·2Br^-(12-6-12)与DNA之间的相互作用. 研究结果表明, 与传统表面活性剂相比, 偶联表面活性剂特殊的分子结构使其与DNA的作用更强烈. DNA引导表面活性剂在其链周围形成类胶束结构, 开始形成类胶束时对应的表面活性剂临界聚集浓度(CAC)比纯表面活性剂临界胶束浓度(CMC)低两个数量级. CAC与DNA的浓度无关, 而与表面活性剂之间的疏水作用以及表面活性剂与DNA之间的静电吸引作用密切相关. Zeta 电位和凝胶电泳结果显示了DNA链所带负电荷逐渐被阳离子表面活性剂中和的过程. 借助原子力显微镜(AFM)成功观察到了松散的线团状DNA, 球状体随机地分散在DNA链上形成类似于串珠的结构、尺寸较大的球形复合物以及其由于吸附多余的表面活性剂重新带正电而被溶解得到的较小DNA/12-6-12聚集体. 圆二色(CD)光谱结果显示, 12-6-12可以诱导DNA的构象发生改变.     

Salt effect on complex formation of neutral/polyelectrolyte block copolymers and oppositely charged surfactants

The salt effect on the complex formation of poly(acrylamide)- block-poly(sodium acrylate) (PAM- b-PAA) as a neutral-anionic block copolymer and dodecyltrimethylammonium bromide (DTAB) as a cationic surfactant at different NaBr concentrations, CNaBr, was investigated by turbidimetric titration, steady-state fluorescence spectroscopy, and dynamic light scattering. At C NaBr < 0.25 M, DTAB molecules may form micelle-like aggregates on PAM- b-PAA chains to form a PAM- b-PAA/DTAB complex above the critical surfactant concentration C critical for the onset of complex formation. In the region of relatively high turbidity, a larger complex is likely to form a core-shell structure, of which the core is a dense and disordered microphase made of surfactant micelles connected by the PAA blocks. The corona was a diffuse shell of PAM chains, and it ensured steric stability. At CNaBr = 0.25 M, a higher electrostatic intermicellar repulsion and intercomplex repulsion induced by a large amount of bound DTAB micelles may lead to a redissolution of large colloidal complexes into intrapolymer complexes. Moreover, a salt-enhancing effect on the complex formation was observed in the PAM- b-PAA/DTAB system; the critical surfactant concentration decreased with increasing salt concentration at CNaBr < 0.10 M. The salt-enhancing effect is due to the larger increase of interaction in comparison to the screening of the interaction.     

Hydrophobic and electrostatic interactions in the mixture hydrolyzed polyacrylamide–N-dodecylpyridinium chloride (AD37–DPC) in aqueous solution

The interactions of oppositely charged polyelectrolyte and surfactant (anionic polyacrylamide AD37 and dodecylpyridinium chloride DPC, respectively) in aqueous solution were studied at 25 °C by measurement of viscosity and conductivity. The system was investigated in aqueous medium in the absence and presence of NaCl. The AD37 interacts strongly with the DPC surfactant of the opposite charge. The interactions are electrostatic and hydrophobic. Thus, they are manifested in the formation of hydrophobic aggregates. The critical aggregation concentration (CAC) is much lower than the critical micellar concentration (CMC) of the surfactant alone. However, the value of the saturation concentration X ₂ is higher. The ionic strength of the medium after addition of salt explains an important part of these interactions. In fact, the electrolyte charge affects the CMC and the CAC values.     

Fluorescence Probe Study of the Interaction Between Acrylic Acid-co-Ethyl Methacrylate Copolymers and Sodium Dodecylsulfate

The interaction between sodium dodecylsulfate (SDS) and acrylic acid (AA)–ethyl methacrylate (EMA) copolymers has been investigated using steady state fluorescence and conductimetric measurements to assess the effect of the polymer composition on the aggregation process. Micropolarity studies using the ratio between the emission intensities of the vibronic bands of pyrene (I₁/I₃) and the shift of the fluorescence emission of pyrene-3-carboxaldehyde show that the interaction of SDS with AA-EMA copolymers occurs at surfactant concentrations smaller than that observed for the pure surfactant in water and depends on the copolymer composition. The increase of ethyl methacrylate in the copolymers lowers the critical aggregation concentration (CAC) due to the larger hydrophobic character of the polymer backbone. The formation of aggregates on the macromolecule is induced mainly by hydrophobic interactions, but the process is also influenced by the ionic strength due to the counter-ions of the polyelectrolyte.     

Salt effect on the complex formation between cationic gemini surfactant and anionic polyelectrolyte in aqueous solution

Salt effect on the interaction of anionic polyelectrolyte sodium carboxymethylcellulose (NaCMC) with cationic gemini surfactant hexamethylene-1,6-bis(dodecyldimethylammonium bromide) [C12H25(CH3)2N(CH2)6N(CH3)2C12H25]Br2 (C12C6C12Br2) has been investigated using turbidimetric titration, steady-state fluorescence, and mobility measurement. It is found that the critical aggregation concentration(cac) for C12C6C12Br2/NaCMC complexes depends little on addition of sodium bromide (NaBr). However, in the presence of nonionic surfactant Triton X-100 (TX100), the critical ionic surfactant mole fraction for the onset of complex formation (Yc) increases markedly with increasing NaBr concentration. These salt effects are supposed as the overall result from competition between the increase of interaction and the screening of interaction. The increase of interaction is referred to as the effect that the larger micelle with higher surface charge density induced by salt has a stronger interaction with oppositely charged polyelectrolyte. The screening of interaction is referred to as the salt screening of electrostatic attraction between the polymer chain and the surfactant. For complex formation between C12C6C12Br2 and NaCMC, the increase of interaction probably compensates the screening of interaction, leading to constant cac values at different salt concentrations. For complex formation between the C12C6C12Br2/TX100 mixed micelle and NaCMC, the screening of interaction probably plays a dominant role, leading to higher suppression of electrostatic binding of micelles to polyelectrolyte.     

The sphere-rod transition of micelles of dodecyldimethylammonium bromide in aqueous NaBr solutions,and the effects of counterion binding on the micelle size,shape and structure

Micelle size and shape of dodecyldimethylammonium bromide have been determined by measurement of light scattering from its aqueous NaBr solutions. In water and in the presence of NaBr up to 0.07 M, the Debye plots give straight lines with positive slopes, and spherical micelles having molecular weight less than 30 000 are formed. At higher NaBr concentrations, the Debye plots decrease with increasing micelle concentration, indicating the aggregation of the primary spherical micelles into larger secondary micelles. The molecular weight and the radius of gyration of the secondary micelles increase with increasing NaBr concentration, and the relation between molecular weight and radius of gyration suggests that they are rodlike and flexible. Linear logarithmic relations between micelle molecular weight and ionic strength hold for spherical and rodlike micelles, respectively, and the threshold concentration of NaBr for the sphere-rod transition is located at 0.07 M. The spherical micelle of dodecyldimethylammonium ions has a size more than 20 surfactant ions larger in NaBr solutions than in NaCl solutions, and their rodlike micelle has a shorter length in NaBr solutions than in NaCl solutions, when compared at an identical aggregation number, indicating 2 more surfactant ions in its cross-section.     

Binding of oppositely charged surfactants to spherical polyelectrolyte brushes: a study by cryogenic transmission electron microscopy

The formation of a complex between an anionic spherical polyelectrolyte brush (SPB) and the cationic surfactant cetyltrimethylammonium bromide (CTAB) is investigated. The SPB consists of long chains of the strong polyelectrolyte poly(styrene sulfonate) (PSS), which are bound chemically to a solid poly(styrene) core of 56 nm in radius. The SPB are dispersed in water, and the ionic strength is adjusted by addition of NaBr. The resulting complexes are investigated in dilute solution by dynamic light scattering, by electrophoretic light scattering, and by cryogenic transmission electron microscopy (cryo-TEM). The formation of the complex between the SPB and the surfactant can be monitored by a strong shrinking of the surface layer when adding CTAB to dilute suspensions (0.01 wt %) and by a decrease of the effective charge of the complexes. Complex formation starts at CTAB concentrations lower than the critical micelle concentration of this surfactant. If the ratio r of the charges on the SPB to the charge of the added surfactant is exceeding unity, the particles start to flocculate. Cryo-TEM images of the complexes at r = 0.6 measured in salt-free solution show that the surface layer composed of the PSS chains and the adsorbed CTAB molecules is partially collapsed: A part of the chains form a dense surface layer while another part of the chains or aggregates thereof are still sticking out. This can be deduced from the cryo-TEM micrographs as well as from the hydrodynamic radius, which is still of appreciable magnitude. The 1:1 complex (r = 1.0) exhibits a fully collapsed layer formed by the PSS chains and CTAB. If the complex is formed in the presence of 0.05 M NaBr, r = 0.6 leads to globular structures directly attached to the surface of the core particles. All structures seen in the cryo-TEM images can be explained by a collapse transition of the surface layer brought about by the hydrophobic attraction between the polyelectrolyte chains that became partially hydrophobic through adsorption of CTAB.     

Hydrotrope-induced inversion of salt effects on the cloud point of an extended surfactant

We report on the effects of electrolytes spanning a range of anions (NaOc, NaSCN, NaNO(3), NaBr, NaCl, NaBu, NaOAc, Na(2)SO(4), Na(2)HPO(4), and Na(2)CO(3)) and cations (LiCl, NaCl, KCl, CsCl, and choline chloride) on the aqueous solubility of an extended surfactant. The surfactant is anionic with a long hydrophobic tail as well as a significant fraction of propylene oxide groups and ethylene oxide groups (C(12-14)-PO(16)-EO(2)-SO(4)Na, X-AES). In the absence of electrolytes, X-AES exhibits a cloud-point temperature that decreases with increasing surfactant concentration. After the addition of salts to the surfactant solutions, various shifts in the solubility curves are observed. These shifts follow precisely the same Hofmeister series that is found for salting-in and salting-out effects in protein solutions. In the presence of different concentrations of sodium xylene sulfonate (SXS), the solubility of the surfactant increases. In this context, SXS can be considered to be a salting-in salt. However, when the electrolytes are added to an aqueous solution of X-AES and SXS the Hofmeister series reverses for divalent anions such as Na(2)SO(4), Na(2)HPO(4), and Na(2)CO(3). Studies on the phase behavior and micelle structures using polarization microscopy, freeze-etch TEM, and NMR measurements indicate a dramatic change in the coexisting phases on the addition of SXS.     

Interaction Between 1-Dodecyl-3-Methylimidazolium Bromide and Sodium Carboxymethylcellulose in Aqueous Solution: Effect of Polymer Concentration

Effect of the concentration of water-soluble polyanion (sodium carboxymethylcellulose, NaCMC) on the interaction between a cationic surfactant (1-dodecyl-3-methylimidazolium bromide, C₁₂mimBr) and NaCMC in aqueous solution has been studied by isothermal titration microcalorimetry (ITC), conductivity, surface tension, and rheological measurements. From the surfactant/polymer interacting enthalpy, it can be deduced that the electrostatic attraction between the cationic surfactant and anionic polyelectrolyte causes an endothermic process, and the C₁₂mimBr monomers binding to the NaCMC chains to form micelle-like aggregates through hydrophobic interaction is an exothermic process. Increasing the NaCMC concentration causes the interaction between C₁₂mimBr and NaCMC to decrease, and the characteristic surfactant concentrations, including the critical aggregation surfactant concentration (CAC), the surfactant concentration to form free micelles (C_m), and the saturation concentration of surfactant on the NaCMC chains (C_S) to increase. Because of the strong electrostatic interaction between C₁₂mimBr and NaCMC, the formation of C₁₂mimBr/NaCMC complexes can lead to precipitation or redissolution depending on solution composition, so the critical precipitation concentration (C_P) and the onset of a redissolution concentration (C_R) has been determined by the electrical conductivity. The rheological results reveal a dramatic increase in solution viscosity around the CAC, attributed to interpolymer cross-linking through the formation of mixed micelles involving the carboxylic acid groups of NaCMC and the surfactant.     

Precipitating Sodium Dodecyl Sulfate to Create Ultrastable and Stimulable Foams

Ultrastable foams are made very simply by adding salt (NaCl or KCl) to sodium dodecyl sulfate. The addition of high concentrations of salt leads to the precipitation of the surfactant on the bubble surfaces and as crystals in the interstices between the bubbles. As a consequence, the ageing of the foams is stopped to make them stable indefinitely, or until they are heated above the melting temperature of the crystals. The use of KCl is shown to be much more effective than that of NaCl because potassium dodecyl sulfate has a higher melting temperature and faster rates of crystallization. The crystalline structures have been investigated inside the foam using small angle neutron scattering. The larger lattice spacing of the crystals formed with NaCl in comparison with KCl has been evidenced. These simple temperature stimulable foams could have many potential applications.     

Microstructure of un-neutralized hydrophobically modified alkali-soluble emulsion latex in different surfactant solutions

At low pH conditions and in the presence of anionic, cationic, and nonionic surfactants, hydrophobically modified alkali-soluble emulsions (HASE) exhibit pronounced interaction that results in the solubilization of the latex. The interaction between HASE latex and surfactant was studied using various techniques, such as light transmittance, isothermal titration calorimetry, laser light scattering, and electrophoresis. For anionic surfactant, noncooperative hydrophobic binding dominates the interaction at concentrations lower than the critical aggregation concentration (CAC) (C < CAC). However, cooperative hydrophobic binding controls the formation of mixed micelles at high surfactant concentrations (C > or = CAC), where the cloudy solution becomes clear. For cross-linked HASE latex, anionic surfactant binds only noncooperatively to the latex and causes it to swell. For cationic surfactant, electrostatic interaction occurs at very low surfactant concentrations, resulting in phase separation. With further increase in surfactant concentration, noncooperative hydrophobic and cooperative hydrophobic interactions dominate the binding at low and high surfactant concentrations, respectively. For anionic and cationic surfactant systems, the CAC is lower than the critical micelle concentration (CMC) of surfactants in water. In addition, counterion condensation plays an important role during the binding interaction between HASE latex and ionic surfactants. In the case of nonionic surfactants, free surfactant micelles are formed in solution due to their relatively low CMC values, and HASE latexes are directly solubilized into the micellar core of nonionic surfactants.     

Removal of organic dyes from water by liquid-liquid extraction using reverse micelles

In the present work, solvent extraction using reverse micelles is proposed for the removal of organic dyes from water. In this approach, the dye is solubilized in the aqueous core of the reverse micelles, which are present in the organic phase. The organic phase is subsequently separated from the aqueous phase leading to signifi-cant removal of dye. Experimental results reveal that the electrostatic interaction between the oppositely charged surfactant head group present in the reverse micelles and the dye molecule plays a key role in the separation. The removal of the anionic methyl orange dye from water is carried out in the presence of cationic hexadecyltrimethyl ammonium bromide surfactant, whereas the removal of the cationic methylene blue dye is carried out in the presence of anionic sodium dodecylbenzene sulfonate surfactant. Amyl alcohol is used as the solvent. The influence of parameters such as dye concentrations, surfactant concentrations, pH, and KCl and NaBr concentrations on the percentage removal of dye was studied. The percentage removal of dye is decreased with the increase in dye concentration in the feed. The increase in surfactant concentration resulted in higher dye removal, because more reverse micelles could be hosted in the organic phase. The increase in aqueous phase pH resulted in enhanced removal of methyl orange from water, while in the case of methylene blue the percentage removal decreased. The increase in KCl and NaBr concentrations resulted in decreased percentage removal of methylene blue, whereas the percentage removal of methyl orange was increased. The effect of pH and salt concentration is explained based on charge transfer mechanism and electrostatic interactions and dye-surfactant complex formation.     

The impact of electrolyte on the adsorption of sodium dodecyl sulfate/polyethyleneimine complexes at the air-solution interface

The addition of electrolyte (0.1 M NaCl) is shown to have a significant impact upon the surfactant concentration and solution pH dependence of the adsorption of sodium dodecyl sulfate (SDS)/polyethyleneimine (PEI) complexes at the air-solution interface. Substantial adsorption is observed over a wide surfactant concentration range (from 10(-6) to 10(-)2 M), and over much of that range of concentrations the adsorption is characterized by the formation of surface multilayers. The surface multilayer formation is most pronounced at high pH and for PEI with a lower molecular weight of 2K, compared to the higher molecular weight of 25K. These results, obtained from a combination of neutron reflectivity and surface tension, highlight the substantial enhancement in surfactant adsorption achieved by the addition of a combination of the polyelectrolyte, PEI, and a simple electrolyte. Furthermore the effect of electrolyte on the pH dependence of the adsorption further highlights the importance of the hydrophobic interaction in surface surfactant/polyelectrolyte complex formation.     

新型疏水缔合聚合物P(AM/POEA)与表面活性剂的相互作用

采用粘度法、荧光探针和透射电镜研究了新型疏水缔合聚合物P(AM/POEA)和表面活性剂SDS和CTAB在水溶液中的相互作用. 聚合物P(AM/POEA)结构中, 疏水体(2-苯氧乙基丙烯酸酯)呈嵌段状无序地分布在聚丙烯酰胺主链上. 这类聚合物很容易和表面活性剂相互作用, 通过疏水缔合, 形成混合胶束状聚集体, 导致溶液粘度剧增. 随聚合物溶液中SDS的加入, 溶液粘度发生大幅度起伏变化, 出现最大值. 粘度最大值对应的表面活性剂浓度c_S,max位于表面活性剂CMC附近, 并发现它的位置不随聚合物微结构而变化. 然而它们缔合作用的增粘程度却与聚合物疏水体含量X_H及疏水嵌段尺寸N_H有关. 在实验浓度范围内, X_H和N_H愈大, 溶液的粘度越高. 此外用透射电镜直接观察到聚合物/表面活性剂体系中聚集体的交联结构形貌.     

正离子Gemini表面活性剂/负离子聚电解质相互作用的研究

摘要 采用荧光探针法和电导法研究了正离子偶联表面活性剂(C₁₂H₂₅(CH₃)₂N-(CH₂)₆-N(CH₃)₂C₁₂H₂₅•2Br) (12-6-12• 2Br^－)和带相反电荷聚电解质聚丙烯酸钠(NaPA)的相互作用, 结果表明: 由于静电相互作用, 12-6-12•2Br^－和NaPA之间可以形成类胶束或复合物. 对比十二烷基三甲基溴化铵(DTMAB)与NaPA复配体系的荧光光谱, 发现偶联表面活性剂与NaPA的相互作用强于传统表面活性剂. 此外, 还研究了盐和醇对偶联表面活性剂/聚丙烯酸钠的复配体系微极性的影响, 发现盐和醇对表面活性剂在聚电解质上形成类胶束和复合物的溶解都有一定的促进作用.     

Studies on the interaction of poly(4-vinylpyridiniumchloride) with poly(sodiumphosphate) in an aqueous solution by conductometry

A reaction between poly(4-vinylpyridiniumchloride) and poly(sodiumphosphate) in the presence and absence of NaCl and NaBr salts was studied in aqueous solution by conductometry. The interaction of polycation and polyanion gave insoluble polyelectrolyte complex which contained polycation and polyanion in unit mole ratio in a salt-free solution. A deviation from stoichiometry was observed at high polyion concentration and in the presence of NaCl and NaBr salts. The resultant complex showed swelling property in different solvent mixtures. A maximum degree of swelling was obtained in the solvent mixture of NaBr + water and NaBr + water + acetone. Furthermore, polyelectrolyte complex sorbed salts from aqueous electrolyte solutions. The sorption of salts increased with increasing salt concentration. © 1996 John Wiley & Sons, Inc.     

Water solubilization capacity of mixed reverse micelles: effect of surfactant component, the nature of the oil, and electrolyte concentration

Solubilization of water in mixed reverse micellar systems with anionic surfactant (AOT) and nonionic surfactants (Brijs, Spans, Tweens, Igepal CO 520), cationic surfactant (DDAB)-nonionic surfactants (Brijs, Spans, Igepal CO 520), and nonionic (Igepal CO 520)-nonionics (Brijs, Spans) in oils of different chemical structures and physical properties (isopropyl myristate, isobutyl benzene, cyclohexane) has been studied at 303 K. The enhancement in water solubilization has been evidenced in these systems with some exceptions. The maximum water solubilization capacity (omega(0,max)) in mixed reverse micellar systems occurred at a certain mole fraction of a nonionic surfactant, which is indicated as X(nonionic,max). The addition of electrolyte (NaCl or NaBr) in these systems tends to enhance their solubilization capacities further both at a fixed composition of nonionic (X(nonionic); 0.1) and at X(nonionic,max) at 303 K. The maximum in solubilization capacity of electrolyte (omega(max)) was obtained at an optimal electrolyte concentration (designated as [NaCl](max) or [NaBr](max)). All these parameters, omega(0,max) vis-a-vis X(nonionic,max) and omega(max) vis-a-vis [NaCl](max), have been found to be dependent on the surfactant component (content, EO chains, and configuration of the polar head group, and the hydrocarbon moiety of the nonionic surfactants) and type of oils. The conductance behavior of these systems has also been investigated, focusing on the influences of water content (omega), content of nonionics (X(nonionic)), concentration of electrolyte ([NaCl] or [NaBr]), and oil. Percolation of conductance has been observed in some of these systems and explained by considering the influences of the variables on the rigidity of the oil/water interface and attractive interactions of the surfactant aggregates. Percolation zones have been depicted in the solubilization capacity vs X(nonionic) or [electrolyte] curves in order to correlate with maximum in water or electrolyte solubilization capacity. The overall results, obtained in these studies, have been interpreted in terms of the model proposed by Shah and co-workers for the solubility of water in water-in-oil microemulsions, as their model proposed that the two main effects that determine the solubility of these systems are curvature of the surfactant film separating the oil and water and interactions between water droplets.