Microemulsion Area Research Articles

Microemulsions and liquid crystalline formulated with triacylglycerols: Effect of ethanol and oil unsaturation

Pseudo-ternary phase diagrams were constructed in order to evaluate the effect of the prevailing oil unsaturation and cosurfactant concentration on the phase behavior of systems prepared with sunflower oil or high oleic sunflower oil (HOSO), water, Tween 80 and ethanol. The phase diagrams showed small areas of one single translucid phase with production of water-in-oil (L2) and oil-in-water (L1) microemulsions. A higher cosurfactant concentration increased microemulsion area and allowed solubilize more water using lower surfactant content. Moreover, small angle X-ray scattering (SAXS) measurements showed that depending of the composition the surfactant self-assembly led to lamellar (Lα) or hexagonal (H1) structures. Microemulsions showed Newtonian behavior, while Lα and H1 showed shear-thinning behavior, viscoelasticity and thixotropy. This more complex rheological behavior was accentuated at lower cosurfactant concentration and with the less unsaturated oil, showing that both oil unsaturation and ethanol content exerted influence on systems properties. However, the higher concentration ethanol masked the effect of oil unsaturation.

Microemulsion as a tool for the transdermal delivery of ondansetron for the treatment of chemotherapy induced nausea and vomiting

The main objective of this study was to develop a microemulsion (ME) formulation for transdermal delivery of ondansetron for chemotherapy induced nausea and vomiting (CINV). For the formulation development oil was selected on the basis of drug solubility in it while the surfactants and co-surfactants (Smix) were screened on the basis of their capacity to solubilize the oil as well as their efficiency to provide the microemulsion area. The microemulsion existence ranges were defined through the construction of the pseudo-ternary phase diagram and various formulations were developed. Effect of surfactant and cosurfactant mass ratio (Smix) on the microemulsion formation and its permeation through excised rat skin was studied. A significant increase in permeability parameters such as steady-state flux (Jss), permeability coefficient (Kp), and enhancement ratio (ER) was observed in ME. Formulation B4 which consisted of 0.5% (w/w) of ondansetron, 5% (w/w) of oleic acid, 30% (w/w) Smix (2:1, Tween 20 and PEG 400) and 64.5% (w/w) of distilled water showed the best permeability profile. The formulation B4 was subjected to various in vitro attributes and converted to microemulsion gel (OMG). In order to predict the efficacy, pharmacokinetic studies were performed and pharmacokinetic profile was compared with ondansetron conventional gel (OCG) and oral marketed syrup (ONDANZ). The absorption of ondansetron from OMG resulted in 6.03 fold increase in bioavailability as compared to oral conventional syrup and 9.66 times with reference to the OCG gel. The future perspective includes preclinical, toxicological and clinical studies for developing clinically viable formulation.

Characterization and evaluation of solid self-microemulsifying drug delivery systems with porous carriers as systems for improved carbamazepine release

The purpose of this study was to investigate solid self-microemulsifying drug delivery system (SSMEDDS), as potential delivery system for poorly water soluble drug carbamazepine (CBZ). Self-microemulsifying drug delivery system (SMEDDS) was formulated using the surfactant polyoxyethylene 20 sorbitan monooleate [Polysorbate 80] (S), the cosurfactant PEG-40 hydrogenated castor oil [Cremophor(®) RH40] (C) and the oil caprylic/capric triglycerides [Mygliol(®) 812] (O). Four different adsorbents with high specific surface area were used: Neusilin(®) UFL2, Neusilin(®) FL2 (magnesium aluminometasilicate), Sylysia(®) 320 and Sylysia(®) 350 (porous silica). Microemulsion area at the surfactant to cosurfactant ratio (K(m)) 1:1 was evaluated and for further investigation SMEDDS with SC/O ratio 8:2 was selected. Solubilization capacity of selected SMEDDS for CBZ was 33.771±0.041 mg/ml. Rheological measurements of unloaded and CBZ-loaded SMEDDS at water content varied from 10 to 60% (w/w) were conducted. It has been found that CBZ has great influence on rheological behaviour of investigated system upon water dilution. Photon correlation spectroscopy has shown the ability of CBZ-loaded SMEDDS to produce microemulsion droplet size. SSMEDDS improved release rate of CBZ, but the type of adsorbent significantly affects release rate of CBZ. For SSMEDDS with different magnesium aluminometasilicate adsorbents, release rate of CBZ decreased with increasing specific surface area due to entrapment of liquid SMEDDS inside the pores and its gradual exposure to dissolution medium. With porous silica adsorbents no difference in release rate was found in comparison to physical mixtures. In physical mixtures at 12.5% (w/w) CBZ content, presence of amorphous CBZ led to high dissolution rate.

Phase Diagrams, Density, and Viscosity for the Pseudoternary System of {Propan-2-yl Tetradecanoate (IPM) (1) + [Tween 80 (21) + Propan-1-ol (22)] (2) + Water (3)}

In this work, a microemulsion system composed of propan-2-yl tetradecanoate (IPM) as oil, polyoxyethylene (20) sorbitan monooleate (Tween 80) as surfactant, propan-1-ol as cosurfactant, and water as the hydrophilic phase has been prepared. The pseudoternary phase diagram of {IPM (1) + [Tween 80 (21) + propan-1-ol (22)] (2) + water (3)} at 303.15 K has been constructed at a constant surfactant to cosurfactant mass ratio of 0.5:1. The phase diagram shows the area of microemulsion. Densities and viscosities were measured in the microemulsion area along three water dilution lines. A maximum viscosity is observed along the water dilution line, which indicates a structural transition from water-in-oil, to a bicontinuous state, and then inversion, to the state of oil-in-water.

Rational formulation development and in vitro assessment of SMEDDS for oral delivery of poorly water soluble drugs

The aims of this study were to formulate a self-microemulsifying drug delivery system (SMEDDS) by a rational formulation approach using mixture experimental design and to derive general concepts that make the development of such systems more feasible. Various types of oils and surfactants were systematically combined and the phase behaviour upon dilution with simulated gastric fluid examined by construction of phase diagrams. The systems solubilising the highest amount of simulated gastric fluid in the continuous microemulsion area were selected for investigation and optimisation of drug solubility. Simvastatin was added as a poorly water-soluble, lipophilic model drug. Two different mixture experimental designs using D-optimal design were set up and used to investigate the solubility of simvastatin in the SMEDDS before and after dilution with simulated gastric fluid respectively. The solubility in each mixture region was analysed by fitting quadratic models using partial least squares analysis. The established models revealed the influence of mixture components on phase behaviour and drug solubility and gave the rationale for formulation optimisation. This study demonstrated that the development of complex self-emulsifying formulations with sufficient solubilisation capacity for poorly water-soluble drugs upon oral administration can be more feasible when using experimental design.

The Effect of Fatty Acid on Phase Behaviors of Tween 80/bmimPF<sub>6</sub>/toluene Microemulsions

Pseudo ternary phase diagrams of bmimPF6/Tween80/fatty acid/toluene systems were constructed with different linear-chain fatty acid. The results demonstrated that when surfactant/fatty acid weight ratio increased, the microemulsion domain became larger, but was less than that in the absence of fatty acid. Moreover, the different chain length of fatty acid affected the extent of microemulsion region, and medium-chain length of fatty acid maximized the single-phase area of bmimPF6-based microemulsion. In addition, the influence on the microstructure of the single-phase area in the different linear-chain length fatty acids was conducted by studying the electrical conductivity behavior. Preliminary investigation suggested that the O/IL (oil /ionic liquid) microemulsion in the presence of C5H11COOH and the IL/O (ionic liquid/oil) microemulsion in the presence of C3H7COOH were max.

Water Solubilization Using Nonionic Surfactants from Renewable Sources in Microemulsion Systems

In this study the effect of temperature, NaCl and oils (hydrocarbons: C8–C16) on the formation and solubilization capacity of the systems of oil/monoacylglycerols (MAG):ethoxylated fatty alcohols (CEO20)/propylene glycol (PG)/water was investigated. The effects of the surfactant mixture on the phase behavior and the concentration of water or oil in the systems were studied at three temperatures (50, 55, 60 °C) and with varied NaCl solutions (0.5; 2; 11%). Electrical conductivity measurement, FTIR spectroscopy and the DSC method were applied to determine the structure and type of the microemulsions formed. The dimension of the microemulsion droplets was characterized by dynamic light scattering. It has been stated that the concentration of CEO20 has a strong influence on the shape and extent of the microemulsion areas. Addition of a nonionic surfactant to the mixture with MAG promotes an increase in the area of microemulsion formation in the phase diagrams, and these areas of isotropic region did not change considerably depending on the temperature, NaCl solution and oil type. It was found that, depending on the concentration of the surfactant mixture, it was possible to obtain U-type microemulsions with dispersed particles size distribution ranging from 25 to 50 nm and consisting of about 30–32% of the water phase in the systems. The conditions under which the microemulsion region was found (electrolyte and temperature—insensitive, comparatively low oil and surfactant concentration) could be highly useful in detergency.

Preparation and optimization of microemulsion of rosuvastatin calcium

Due to very less bioavailability (20%) of Rosuvastatin calcium, an attempt was made to develop and optimize microemulsion formulation. Capmul MCM, Tween 20 and PEG 400 were selected as oil, surfactant and cosurfactant respectively as the drug is having higher solubility in them. 3:1% w/w S:CoS was selected as it gave higher microemulsion area. Optimized batch (ME-1) was selected having 5% Capmul MCM, 50% Tween 20:PEG 400 and 45% water based on evaluation parameters globule size, zeta potential, PDI, % transmittance.

利用纳米粒子强化微乳液体系HCFC141b 水合物的生成

Accelerating the formation of gas hydrate is of great significance for the application of gas hydrate technology in the area of cooling storage. To promote the rapid formation and growth of HCFC141b gas hydrate, the thermodynamically stable HCFC141b microemulsion was successfully prepared with aid of Tween 20/lecithin compound surfactants for increasing interface and compatibility between the refrigerant and water. The hydration process of HCFC141b in the microemulsion system was investigated in terms of induction time and supercooling degree and was compared to that in coarse HCFC141b/water mixture systems with or without surfactant in them. The characteristics of hydrate formation in the different systems were revealed. It is indicated that HCFC141b hydrate can form rapidly and uniformly in the microemulsion system. The induction time of HCFC141b hydration in the microemulsion system was shortened by 36% and 52% compared to that in coarse HCFC141b/water mixture with 1wt% Tween 20 and without any surfactant in it, respectively. Then, considering the characteristics of nano-particles in the enhancement of heat transfer, different amount of nano-Cu particles or nano-Al2O3 particles was added to HCFC141b/water microemulsion system and coarse mixture systems aiming to facilitate HCFC141b hydration process. The addition of nano-Cu to the microemulsion system further shortened the induction time and led to reduced supercooling degree of hydration in the microemulsion system, while it did not function in the coarse mixtures. The promotion degree of nano-Cu on decreasing the induction time as welll as the supercooling degree of hydration was increased with an increase in the amount of nano-particles in the system. By adding 0.1wt% nano-Cu in the microemulsion system, the induction time was shortened by 29% and the supercooling degree was reduced by 39%. In all, combining the characteristics of large interfacial area of microemulsion with that of enhanced mass and heat transfer of nano-fluid by adding nano-particles can be an effective way to promote the formation of gas hydrate.

Phase behaviour, microstructure and ibuprofen solubilization capacity of pseudo-ternary nonionic microemulsions

This study investigated phase behaviour, microstructure and solubilization capacity of pseudo-ternary surfactant/cosurfactant/isopropyl myristate/water systems employing complex mixtures of nonionic surfactants for formation of single-phase microemulsions. The surfactant was PEG-8 caprylic/capric glycerides (Labrasol®). A well defined mixture of octoxynol-12 and polysorbate 20 and/or PEG-40 hydrogenated castor oil, available as commercial nonionic surfactants Solubilisant gamma® 2421, Solubilisant gamma® 2429 and Cremophor® RH 40, respectively, were evaluated as cosurfactants. Surfactant + cosurfactant mixtures were treated as a single component (pseudo-component), since a surfactant-to-cosurfactant weight ratio (Km 50:50) was constant through the study. Phase behaviour study revealed enlargement of single-phase microemulsion area as surfactant + cosurfactant-to-oil weight ratio (SCoS/O) increases. The formation of fully dilutable microemulsions containing the maximum of water incorporation in the surfactant/cosurfactant/oil preconcentrates of W max ≥ 80% w/w, was achieved at SCoS/O 90:10. Microemulsions formed along the single-phase sequence at SCoS/O 90:10 in the presence of different cosurfactants, were characterized using polarized light microscopy, photon correlation spectroscopy (PCS), and rheological measurements. Different performances of complex mixtures of nonionic surfactants in stabilization of single-phase microemulsions were observed only in highly diluted oil-in-water microemulsions area. Investigation of solubilization capacity for poorly soluble drug ibuprofen revealed the critical importance of water-to-surfactant + cosurfactant ratio and penetration of oil at the interface.

Mixture experiment methods in the development and optimization of microemulsion formulations

Microemulsion formulations represent an interesting delivery vehicle for lipophilic drugs, allowing for improving their solubility and dissolution properties. This work developed effective microemulsion formulations using glyburide (a very poorly-water-soluble hypoglycaemic agent) as a model drug. First, the area of stable microemulsion (ME) formations was identified using a new approach based on mixture experiment methods. A 13-run mixture design was carried out in an experimental region defined by constraints on three components: aqueous, oil and surfactant/cosurfactant. The transmittance percentage (at 550 nm) of ME formulations (indicative of their transparency and thus of their stability) was chosen as the response variable. The results obtained using the mixture experiment approach corresponded well with those obtained using the traditional approach based on pseudo-ternary phase diagrams. However, the mixture experiment approach required far less experimental effort than the traditional approach. A subsequent 13-run mixture experiment, in the region of stable MEs, was then performed to identify the optimal formulation (i.e., having the best glyburide dissolution properties). Percent drug dissolved and dissolution efficiency were selected as the responses to be maximized. The ME formulation optimized via the mixture experiment approach consisted of 78% surfactant/cosurfacant (a mixture of Tween 20 and Transcutol, 1:1, v/v), 5% oil (Labrafac Hydro) and 17% aqueous phase (water). The stable region of MEs was identified using mixture experiment methods for the first time.

Study of Pseudoternary Phase Diagram Behaviour and the Effect of Several Tweens and Spans on Palm Oil Esters Characteristics.

Palm oil esters are high molecular weight esters oil that has been newly synthesized by University Putra Malaysia researchers. It has received a lot of attention for its pharmaceutical and chemical application. The aim of this study is to study the effects of the palm oil esters with different HLB surfactant mixture on the ternary diagrams behaviour and to confine the various systems resulted from these combinations. These systems include traditional emulsion, gel area, transpernat micro-emulsion area, O/W and W/O emulsions. In this study, pseudoternary phase diagrams of water, POEs and non-ionic surfactant mixture of several HLB values were constructed using water titration method. The resultant mixtures collected after each addition and mixing of water were analysed visually, along with conductivity, dilution in water and dye test (methylene blue) to classify them as O/W emulsion (transparent and opaque) or W/O (opaque) and liquid or gel. As a conclusion, palm oil esters were found to be suitable for the formulation of different types of emulsion. Additionally, different HLB value of non-ionic surfactant(s) exhibited different pseudoternary phase diagram characteristics. Keywords: palm oil esters, Tween, Span, Pseudoternary phase diagram, O/W emulsion

Design of Self-Emulsifying System Based on QSAR

Quantitative structure-activity relationships (QSARs) were used to design self-emulsifying delivery system. Ab initio calculations were carried out at the HF/6-31G level. The influences of component ratio, stereoscopic effect, hydrophobic interactions, and the electric effect on the microemulsion areas and the size of the self-emulsifying systems were investigated. The microemulsion areas and sizes were correlated to the generated descriptors and the ratio of the components using multiple linear regression analysis (MLR). Validation was carried out by a predictive-ability test. The ratio of surfactant to co-surfactant had the most impact on the phase behavior of the self-emulsifying systems. The size of the self-emulsifying system increased with an increase in the amount of oil and co-surfactant and decreased with an increase in the amount of surfactant. Interactions between the components had little influence on the properties of the systems. The models had significant predictive power except for the model of isopropyl myristate (IPM). QSAR is a new method to investigate the preparation of self-emulsifying systems.

Effect of Alkyl Sulfate on the Phase Behavior of Microemulsions Stabilized with Monoacylglycerols

AbstractIn this study the effect of an anionic surfactant (sodium dodecyl sulfate SDS) and oils (hydrocarbons: C12–C16) on the formation and phase behavior of the systems of oil/monoacylglycerols (MAG):SDS/propylene glycol/water has been investigated. The effects of the surfactant mixture on the phase behavior and the concentration of water or oil in the systems were studied at three temperatures (50, 55, 60 °C). Electrical conductivity measurement, FT‐IR spectroscopy and differential scanning calorimetry methods were applied to determine the structure and type of the microemulsions formed. The dimension of microemulsion droplets was characterized by dynamic light scattering. It has been stated that the concentration of SDS has a strong influence on the shape and extent of the microemulsion areas. Addition of an ionic surfactant to the mixture with MAG promotes an increase in the area of microemulsion formation in the phase diagrams, and these areas of the isotropic region change with the temperature. It was shown that the presence in the systems of a surfactant more hydrophilic than MAG caused an increase in water content in the microemulsions. It was found that, depending on temperature and concentration of the surfactant mixture, it was possible to obtain a W/O type microemulsion with a dispersed particles size distribution ranging from 20 to 50 nm and containing about 17–38% water in the system. Among different alkanes (from C12 to C16), hexadecane embedded microemulsions showed a maximum water solubilization capacity.

Formulation Development of Parenteral Phospholipid-based Microemulsion of Etoposide

The aim of the present study was to investigate the potential of a phospholipid-based microemulsion formulation for parenteral delivery of anticancer drug, etoposide. The microemulsion area was identified by constructing pseudoternary phase diagrams. The prepared microemulsions were subjected to different thermodynamic stability tests. The microemulsion formulations that passed thermodynamic stability tests were characterized for optical birefringence, droplet size, viscosity measurement, and pH measurements. To assess the safety of the formulations for parenteral delivery, the formulation was subjected to compatibility studies with various intravenous infusions and in vitro erythrocyte toxicity study. The developed formulation was found to be robust and safe for parenteral delivery.

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.

MICROEMULSIONS WITH NONIONIC SURFACTANTS AND MIXED OILS

We report on the properties of water/mixed nonionic surfactants/R (+)‐limonene/isopropylmyristate microemulsions. The surfactants were sucrose monolaurate and ethoxylated mono‐di‐glyceride. The total area of the one phase microemulsion region in the pseudoternary phase diagrams is dependent on the mixing ratios (w/w) of the oils and that of the mixed surfactants. The largest microemulsion area formed with a surfactants mixing ratio (w/w) equals unity. The one phase microemulsion area increases with the increase in the R (+)‐limonene/ isopropylmyristate‐mixing ratio (w/w). Electrical conductivity was measured at different temperatures and the activation energy of conduction flow was evaluated. At the percolation threshold, the activation energy of conduction flow reaches a minimum value. Beyond the percolation threshold, a small increase is observed in the activation energy of conduction flow, then it decreases with the increase in the water volume fraction indicating structural transitions. Dynamic viscosity was measured as function of temperature at different water volume fractions. The measured viscosities for the samples in all of the systems decrease as the temperature increases. The thermodynamic parameters of viscous flow that include enthalpy, entropy, and Gibbs free energy were estimated. In all of the systems studied, the enthalpy of viscous flow remains constant as function of temperature and varies as the water content in the microemulsions vary. The entropy and the Gibbs free energy vary with both the temperature and the composition of the microemulsions. Linear relationships were observed between the enthalpy and entropy of viscous flow. The enthalpy‐entropy compensation temperature was determined and found to be 247 K. Small angle X‐ray scattering results indicate that the periodicity increases linearly with the increase in the water volume fraction. The correlation length increases with the increase in the water volume fraction to a certain value, then stabilizes.

Phase behavior of a sodium dodecanol allyl sulfosuccinic diester/n‐pentanol/methyl acrylate/butyl acrylate/water microemulsion system and preparation of acrylate latexes by microemulsion polymerization

AbstractPseudoternary phase diagrams of quaternary microemulsion systems composed of the reactive surfactant sodium dodecanol allyl sulfosuccinic diester, n‐pentanol, methyl acrylate/butyl acrylate, and water were made. The influence of the mass ratio of sodium dodecanol allyl sulfosuccinic diester to the cosurfactant (n‐pentanol) in the system and the influence of electrolyte sodium chloride on the microemulsion area were examined. The microstructure of the microemulsion was determined with a conductance technique. The results suggested that there were three structures in the microemulsion system: water in oil, oil in water, and a bicontinuous phase. Microemulsion polymerizations were carried with some point in the microemulsion region being chosen as the formulation. The structure and configuration of the polymer latexes were determined and analyzed with Fourier transform infrared, differential scanning calorimetry, and scanning electron microscopy. The results suggested that the reactive surfactant could participate in the polymerization with the monomers to some extent; the glass‐transition temperature of the latex was −31.4°C. The polymer latex was transformed gradually from an open porous structure to a closed porous structure when its pregnant microemulsion was varied from a bicontinuous structure to an oil‐in‐water structure. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Water Solubilization in Mixed Nonionic Surfactants Microemulsions

The systems investigated were water/sucrose laurate/ethoxylated mono-di-glyceride/oleic phase. The oleic phase used first was the pure oils R (+)-limonene, isopropylmyristate, and caprylic-capric triglyceride; these oils were then mixed with ethanol at different mixing ratios (w/w). The total area of the one phase microemulsion region is dependent on the mixing ratios (w/w) of the mixed surfactants and that of the ethanol/oil. The largest microemulsion phase area formed with a surfactants mixing ratio (w/w) equals unity. For the systems where the oleic phase was a mixture of oil and ethanol, the total area of the monophasic microemulsion increases with the increase in the ethanol/oil mixing ratio (w/w). The Gibbs free energy of solubilization was estimated. It increases as the mixing ratio (w/w) of ethoxylated mono-di-glyceride/sucrose laurate increases and with the increase in the ethanol/oil mixing ratio (w/w). The Gibbs free energy of solubilization decreases with the increase in the water content in the water-in-oil microemulsions. The values of the Gibbs free energy of solubilization are higher for oil-in-water microemulsions compared to those of the water-in-oil microemulsions.

A study of the properties of mixed nonionic surfactants microemulsions by NMR, SAXS, viscosity and conductivity

The pseudoternary phase behavior of the water/sucrose laurate/ethoxylated mono-di-glyceride/R (+)-limonene systems was investigated for different surfactants mixing ratios ( w/w) at 25 °C. The microemulsion boundaries were determined and the surfactants content at the interface of water- R (+)-limonene was estimated. For surfactants mixing ratio ( w/w) equals unity, the area of the one phase microemulsion region reaches its maximum. The system with the maximum microemulsion area was investigated using electrical conductivity, dynamic viscosity, small angle X-ray scattering, and nuclear magnetic resonance. Electrical conductivity increases as the water volume fraction increases and a percolation threshold was observed. Dynamic Viscosity varies as function of the water volume fraction in a non-monotonic way giving two-peaked plot. The characteristics of the domain size of the microemulsions called periodicity measured by small angle X-ray scattering increases with the increase in the water volume fraction. The correlation length of the domain size reaches a maximum when plotted against the water volume fraction in the microemulsions. Relative diffusion coefficients of water increase and those of oil decrease with increasing the water volume fractions in the microemulsions indicating structural transitions.