Nonionic Surfactant TX-100 Research Articles

Electrochemical observation of individual collision-blocking events of TX-100 nanomicelles: An accurate and universal approach for the critical micelle concentration determination of surfactants

The electrochemical collision-blocking technique, equipped with the nanoelectrode of Pt was proposed for determination of the critical micelle concentration (CMC) of non-ionic surfactant TX-100. The approach was found on detection of individual collided nanomicelles in amperometric measurements of the oxidation of K4Fe(CN)6 varying the titrated concentration of TX-100 whereas the formed micelles above the CMC stick on the electrode surface during collision to locally block the flux of electroactive species and further to change the faradaic current. The step-like current transients observed in i-t curves have been demonstrated corresponding to electrochemical collision events of individual TX-100 micelles and micelle aggregates by 3D COMSOL simulations. The logarithm relations between the collision frequency of micelle(s) and the concentration of TX-100 were derived by regression analysis to give the corresponding values of CMC in salt solutions. Further, an ‘ideal’ CMC of TX-100 without influence of additional salts was estimated to be 0.194 mM using the McDevit-Long theory. The more accurate CMC determined in this work has shown less than the previously reported, mainly due to the detection limit for micelle as low as 0.41 fM. Also, we determined the second CMC of 1.21 mM as the first observation of the collision response of micelle aggregates during TX-100 titration. Owing to its analytical characteristics in single-particle tracking and material insensitivity, the approach we proposed is potentially to be a universal tool for accurate determination of CMC of surfactants, and also for studying the formation of polymer particles at a single-particle level, which is not easily accessible using conventional ensemble measurements.

Effect of caffeine on the micellization and related thermodynamic parameters of sodium dodecyl sulphate, hexadecyltrimethylammonium bromide and triton x-100: a physicochemical study

ABSTRACT Effect of caffeine on the micellization of anionic surfactant (SDS), cationic surfactant (HTAB) and non-ionic surfactant (Tx-100) was investigated using the conductometric and tensiometric techniques. The thermodynamic parameters such as change in Gibbs-free energy, , change in enthalpy of micellization, , change in entropy of micellization, , change in Gibbs-free energy of transfer, , surface excess concentration, , minimum area per surfactant molecule, , surface pressure, , change in Gibbs-free energy of adsorption, and other related parameters were calculated to gain insights into the interactions of caffeine with different surfactants at different temperatures. The CMC in mole fraction units, , values of SDS in caffeine are low, while that of HTAB are large in comparison with the values reported in water. The negative values of and and the positive values of are indicative of SDS-caffeine and HTAB-caffeine interactions.

Resource utilization of chlorosilane residual liquid to prepare nano-silica in reverse microemulsion system

Nano-silica particles were prepared using chlorosilane residual liquid as raw materials in an inverse microemulsion system formed by three different surfactants (TX-100, CTAB, SDS) with n-hexanol, cyclohexane, and ammonia. The phase behavior of inverse microemulsions and the preparation of nano-silica were investigated. The results showed that the system composed of non-ionic surfactant TX-100 had a larger inverse microemulsion region than other two system and was more suitable for the preparation of nano-silica. The prepared nano-silica had uniform sphericity and good dispersibility, the average particle diameter of 31 nm, and the variance of 1 nm. XRD, FT-IR, N2 adsorption/desorption experiments and TG-DSC analysis were used to characterize the prepared nano-silica. The results showed that the prepared nano-silica was amorphous mesoporous silica with a BET specific surface area of 472.5 m2/g. They have a good thermal stability, and the phase structure and main chemical functional groups of nano-silica would not change after calcination at 600 °C, but the nano-silica would undergo a phase change at 1135 °C, which changed from amorphous to crystalline. The new technology not only broadened the source of preparation of nano-silica materials, but also provided new ideas for the treatment of chlorosilane residual liquid and the sustainable development of polysilicon industry.

Selective adsorption of PHC and regeneration of washing effluents by modified diatomite.

Selective removal of petroleum hydrocarbons (PHCs) from soil washing effluents is the key to the surfactant-enhanced soil washing technology. In this study, the diatomite was modified by nonionic surfactant TX-100 and applied in the selective adsorption of PHCs in the soil washing effluents. The modified diatomites were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, N2 adsorption/desorption and X-ray photoelectron spectroscopy respectively. The adsorption process followed the pseudo-second-order model and the adsorption isotherms indicated that the interaction between PHCs and modified diatomite was monolayer adsorption. The important operating factors such as TX-100 dosage, adsorbent dosage, time and temperature were optimized. With the participation of the low-cost adsorbent TX3-Db with high adsorption capacity, the recovery efficiency of the washing effluents was still up to 78.9% after three cycles. A selective adsorption mechanism, based on steric hindrance and electrostatic repulsion, was proposed to explain the removal of PHCs from washing effluents.

Dispersion, sedimentation and aggregation of multi-walled carbon nanotubes as affected by single and binary mixed surfactants.

Two commonly used dispersants, octyl phenol ethoxylate (Triton X-100) and sodium dodecyl sulfate (SDS), were employed to explore the effects of single or mixed surfactants on the dispersion, sedimentation and aggregation of multi-walled carbon nanotubes (MWCNTs). Non-ionic surfactant TX100 showed much superior capability to anionic surfactant SDS in dispersing MWCNTs due to the benzene ring structure in its tail group. The addition of SDS reduced the adsorption of TX100 on the surface of MWCNTs and the consequent suspension of MWCNTs. The dispersing ability of TX100–SDS binary mixture was between those of individual SDS and TX100. The introduction of SDS greatly retarded the sedimentation and aggregation of suspended MWCNTs. The critical coagulation concentration (CCC) values of suspended MWCNTs dispersed by TX100 (2000 mg l−1), SDS (2000 mg l−1) and TX100–SDS (2000 mg l−1 of each component) were 48.6, 398 and 324 mM, respectively, for Na+ treatments. The CCC values were much lower for Ca2+ treatments, which were 30.4 and 32.1 mM, respectively, for MWCNTs dispersed by TX100 and TX100–SDS mixture. Overall, these results demonstrated that although the introduction of SDS did not improve the ability of TX100 in suspending MWCNTs, the suspensions exhibited more stable properties than those dispersed by TX100 alone. Our findings have important implications for the design of surfactant mixtures and the prediction of the behaviour and fate of MWCNTs in the water environment.

Effects of surfactant on the degradation of 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) by nanoscale Ag/Fe particles: Kinetics, mechanisms and intermediates

Surfactants are known to enhance the degradation of halogenated organics by nanoscale zerovalent iron (n-ZVI) or n-ZVI-based bimetallic particles, but the mechanism of the promotion is not well understood. In this study, we used nanoscale Ag/Fe particles (n-Ag/Fe) to degrade 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) in different surfactant solutions. The results show that the nonionic surfactant TX-100 had the best promoting effect, which might be attributed to the decrease in particle agglomeration and improvement of mass transfer efficiency after the adsorption of TX-100 on n-Ag/Fe. The distribution analysis of BDE-47 in solid and liquid phases indicates that when the concentration of TX-100 in aqueous solution was above critical micelle concentration, BDE-47 started to dissolve in the liquid phase. Thus, TX-100 micelles can enhance the mass transfer efficiency of BDE-47. However, a too high concentration of TX-100 (above 1.0 mM) would influence the promotion effect of BDE-47 degration, which might be attributed to the excessive and thicker micelles of TX-100 hindering the contact between BDE-47 and n-Ag/Fe. We also studied the degradation pathway of BDE-47 and its products, and found that surfactants did not change the degradation pathway of BDE-47.

Sorption of triclosan by carbon nanotubes in dispersion: The importance of dispersing properties using different surfactants

The production of carbon nanotubes (CNTs) increased rapidly due to the superior properties and was suggested to be the potential sorbents for environmental remediation. CNTs tend to form aggregates, thus CNTs dispersion was commonly produced by sonication with surfactant in industry for better application. In the present study, a novel passive sampling method was used to systematically study sorption of triclosan to CNTs dispersion to give a better understanding on their interactions especially with the presence of surface-active substances. With the increase of anionic surfactant concentration (SDBS or SDS), sorption of triclosan was gradually suppressed. CNTs dispersed by nonionic surfactant TX-100 increased or decreased sorption at different TX-100 and triclosan concentration. Little amount of cationic surfactant CTAB(1 mg/L) could sharply decrease triclosan sorption to CNTs but with larger CTAB concentration, sorption was continually increased. Sorption isotherms of triclosan to CNTs dispersion with 40 mg/L and 100 mg/L surfactant fitted well with Toth model show the existence of double competition in the sorption process. Different from the adsorption mechanism of previously aggregated CNTs and compounds. Sorption data combined with comprehensive characterization of CNTs dispersion and theoretical analysis, three effects referring to charge, dispersion and competition were proposed. Sorption coefficient was linearly correlated with the characterization parameters. Surface charge, dispersion status and surfactant concentration play the important role on triclosan sorption in CNTs dispersion in the presence of anionic, cationic and nonionic surfactant, respectively. The results provide basic supports on application of CNTs in remediation area and exploring the fate of both CNTs dispersion and pollutants.

Mechanistic study of wettability alteration of oil-wet sandstone surface using different surfactants

Different analytical methods including Fourier transform infrared (FTIR), atomic force microscopy (AFM), zeta potential measurements, contact angle measurements and spontaneous imbibition tests were utilized to make clear the mechanism for wettability alteration of oil-wet sandstone surface using different surfactants. Results show that among three types of surfactants including cationic surfactants, anionic surfactants and nonionic surfactants, the cationic surfactant CTAB demonstrates the best effect on the wettability alteration of oil-wet sandstone surface. The positively charged head groups of CTAB molecules and carboxylic acid groups from crude oil could interact to form ion pairs, which could be desorbed from the solid surface and solubilized into the micelle formed by CTAB. Thus, the water-wetness of the solid surface is improved. Nonionic surfactant TX-100 could be adsorbed on oil-wet sandstone surface through hydrogen bonds and hydrophobic interaction to alter the wettability of oil-wet solid surface. The wettability alteration of oil-wet sandstone surface using the anionic surfactant POE(1) is caused by hydrophobic interaction. Due to the electrostatic repulsion between the anionic surfactant and the negatively charged surface, POE(1) shows less effect on the wettability alteration of oil-wet sandstone surface.

Transport properties of aqueous ionic liquid microemulsions: influence of the anion type and presence of the cosurfactant

Transport properties, viz. specific conductivity, dynamic viscosity and apparent diffusion coefficients, were measured as a function of water content in aqueous ionic liquid microemulsions containing 1-butyl-3-methylimidazolium hexafluorophosphate, [BMIM][PF6] and bis(trifluoromethanesulphonyl)imide, [BMIM][Tf2N], stabilized by the nonionic surfactant TX-100, or its mixture with a cosurfactant, i.e. butanol. The investigation covered the whole water content range through various (Winsor I-III and dissolved solution) structures of the system. The comparative approach allowed closer inspection into phenomena being on the background of observed transport properties behavior taking into account the influence of the cosurfactant. The addition of butanol offers considerable advantages, such as an increase in conductivity, especially in systems containing ionic liquids with lower conductivity. This is accompanied by a significant decrease in viscosity, even to values that are comparable with those of molecular solvents. Moreover, the reasons for the surprisingly higher conductivity of [BMIM][PF6]-based systems were provided, and the conclusions were supported by cyclic voltammetry as well as spectrophotometric and dynamic light scattering measurements.

Characteristics of mixed systems of phenol red and cetylpyridinium chloride

Dye–surfactant systems known to exhibit two critical micelle concentrations (cmcs) are not many and the behavior of such systems in the mixed form has not been fully explored and reported. Phenol red (PR) and cetylpyridinium chloride (CPC) form one such dye–surfactant pair and its mixtures are studied here in the entire composition range using surface tension, conductance and UV–Visible spectroscopy methods. In this mixed system, mixed micelles are formed with one cmc in the region of 0<αCPC<0.5, while mixed micelles as well as micelles of the surfactant alone are formed with two cmcs if 0.5≤αCPC<1 (αCPC is the mole ratio of CPC to PR in solution). The mixture shows strong synergism in cmc with high negative value for interaction parameter. The bathochromic shift of the 432nm band indicated hydrogen bonding between PR− species in the region of αCPC<0.4 and this hydrogen bonding weakened more in the presence of CPC due to ion pair formation than in the presence of a non-ionic surfactant TX-100. The relative amount of CPC in the mixture and the nature of the surfactant are found to influence the maximum wavelength of the PR2− band also. The excess standard free energy of micellization has a linear correlation with the interaction parameter. Surface excess values of the individual components of the mixed system were evaluated. The compositions of the mixed micelle and the adsorbed layer reveal that some CP+ monomers also aggregate/adsorb along with the CP+–PR− ion pairs.

Study of Spontaneous Imbibition of Water by Oil-Wet Sandstone Cores Using Different Surfactants

The mechanism of spontaneous imbibition of water by sandstone cores and the relationship between reservoir wettability and imbibition recovery were studied by investigating factors influencing the spontaneous imbibition of different surfactants by oil-wet sandstone cores. Ultimate oil recovery of cores using the cationic surfactant CTAB was higher than that of the cores using the nonionic surfactant TX-100 and the anionic surfactant POE (1) at the same concentration. For CTAB and TX-100, the ultimate oil recovery by spontaneous imbibition increased with increase in surfactant concentration. In regard to imbibition recovery, TX-100 and POE(1) at high temperatures were superior to those at low temperatures. Ultimate oil recovery of the high-permeability core was higher than that of the low-permeability core at room temperature. According to changes in the driving force during the imbibition process, the imbibition curve could be divided into three regions: (1) mainly capillary force, (2) both capillary and gravity forces, and (3) mainly gravity force. The stronger the hydrophilicity of the rock surface, the higher the spontaneous imbibition recovery.

Preparation of SiO2 /epoxy nanocomposite via reverse microemulsion in situ polymerization

Reverse water/oil (w/o) microemulsions composed of epoxy resin (EP) (the oil phase) and nonionic surfactant and ammonia aqueous solutions (the water phase) were used in the synthesis of SiO2/EP nanocomposites. The stability of reverse microemulsion was evaluated by measuring water solubilization of the microemulsion. Effects of surfactant type and content, ammonia concentration and temperature on the water solubilization were systematically investigated. Higher water solubilization capacity was obtained by nonionic surfactant TX-100 compared with other two surfactants, Span-80 and Tween-80. Ammonia concentration of 5 wt% and preparation temperature at 35°C were favorable for forming a stable microemulsion and enabling the subsequent hydrolysis and condensation reaction of inorganic precursor tetraethoxysilane (TEOS). SiO2/ epoxy nanocomposites were prepared via in situ polymerization of TEOS within the nanoscale reverse microemulsion “water pool”. FTIR, SEM, and universal testing machine were used to characterize the structural and mechanical properties of the composite. The results revealed that the optimal mechanical properties were obtained at 3 wt% TEOS content. Compared with neat epoxy resin, the tensile and flexural strength of the composite were 40% and 12% higher, respectively. The formation of the silica structure in the hybrid was investigated with FTIR. The SEM and optical observations showed a ductile fracture morphology and good miscibility between inorganic and organic phases. POLYM. COMPOS., 35:1388–1394, 2014. © 2013 Society of Plastics Engineers

Oxidation of Methionine by Colloidal MnO2 in Aqueous and Micellar Media: A Kinetic Study

The oxidation of methionine by freshly prepared colloidal manganese dioxide in aqueous as well as micellar media was studied spectrophotometrically at 35°C. The reaction between methionine and MnO2 in both media exhibits 1:1 stoichiometry (methionine:MnO2). The oxidation reaction is first order with regard to the MnO2 concentration, but is fractional-order in the methionine concentration and HClO4 concentrations. A catalytic effect of nonionic surfactant TX-100 on the rate of oxidation was observed and reaction rate was found to be proportional to {k′ + k″ [TX-100]}, where k′ and k″ are the rate constants in absence and presence of surfactant, respectively. The use of surfactant micelles is highlighted as, in favorable cases; the micelles help the redox reactions by bringing the reactants in a close proximity through hydrogen bonding. The oxidation reaction in aqueous and micellar media is shown to proceed via methionine–MnO2 and methionine–MnO2–TX-100 complexes, respectively, which decomposes slowly in a rate determining step to give methionine sulfoxide as the product. A suitable mechanism is proposed for these observations.

Kinetics of colloidal MnO2 reduction by L-arginine in absence and presence of surfactants

The kinetics of the oxidation of L-arginine by water-soluble form of colloidal manganese dioxide has been studied using visible spectrophotometry in aqueous as well as micellar media. To obtain the rate constants as functions of [L-arginine], [MnO2] and [HClO4], pseudo-first-order conditions are maintained in each kinetic run. The first-order-rate is observed with respect to [MnO2], whereas fractional-order-rates are determined in both [L-arginine] and [HClO4]. Addition of sodium pyrophosphate and sodium fluoride enhanced the rate of the reaction. The effect of externally added manganese(II) sulphate is complex. It is not possible to predict the exact dependence of the rate constant on manganese(II) concentration, which has a series of reactions with other reactants. The anionic surfactant SDS neither catalyzed nor inhibited the oxidation reaction, while in presence of cationic surfactant CTAB the reaction is not possible due to flocculation of reaction mixture. The reaction is catalyzed by the nonionic surfactant TX-100 which is explained in terms of the mathematical model proposed by Tuncay et al. Activation parameters have been evaluated using Arrhenius and Eyring equations. On the basis of observed kinetic results, a probable mechanism for the reaction has been proposed which corresponds to fast adsorption of the reductant and hydrogen ion on the surface of colloidal MnO2.

Ionic Liquid Containing Microemulsions: Probe by Conductance, Dynamic Light Scattering, Diffusion-Ordered Spectroscopy NMR Measurements, and Study of Solvent Relaxation Dynamics

Room-temperature ionic liquid (RTIL), N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide ([P(13)][Tf(2)N]), was substituted for polar water and formed nonaqueous microemulsions with benzene by the aid of nonionic surfactant TX-100. The phase behavior of the ternary system was investigated, and microregions of [P(13)][Tf(2)N]-in-benzene (IL/O), bicontinuous, and benzene-in-[P(13)][Tf(2)N] (O/IL) were identified by traditional electrical conductivity measurements. Dynamic light scattering (DLS) revealed the formation of these IL microemulsions because with gradual increase of RTIL contents the droplet sizes of the microemulsions are also gradually increasing. Pulsed-field gradient spin-echo NMR have been studied to measure the diffusion coefficients of neat [P(13)][Tf(2)N] and [P(13)][Tf(2)N] in microemulsions which indicate ionic liquid containing microemulsions is formed. Moreover, the dynamics of solvent relaxation have been investigated in [P(13)][Tf(2)N]/TX100/benzene microemulsions using steady-state and time-resolved fluorescence spectroscopy using coumarin 153 (C-153) and coumarin 480 (C-480) fluorescence probe with variation of RTIL contents in microemulsions. For both of the probes with increasing amount of ionic liquids in microemulsions the relative contribution of the fast components increases and the slow components contribution decreases; therefore the average solvation time decreases.

Kinetics and mechanism of the reduction of colloidal MnO2 by glycyl-leucine in the absence and presence of surfactants

The kinetics of the reduction of water-soluble colloidal manganese dioxide by glycyl-leucine (Gly-Leu) has been investigated in the presence of perchloric acid both in aqueous as well as micellar media at 35°C. The study was carried out as functions of [MnO2], [Gly-Leu] and [HClO4]. The first-order-rate is observed with respect to [MnO2], whereas fractional-order-rates are determined in both [Gly-Leu] and [HClO4]. Addition of sodium pyrophosphate and sodium fluoride enhanced the rate of the reaction. Further, the use of surfactant micelles is highlighted as, in favourable cases, the micelles help the redox reactions by bringing the reactants into a close proximity due to hydrogen bonding. While the ionic surfactants SDS and CTAB have not shown any effect on the reaction rate, the nonionic surfactant TX-100 has catalytic effect which is explained in terms of the mathematical model proposed by Tuncay et al. (1999). The Arrhenius and Eyring equations are valid for the reaction over the range of temperatures used and different activation parameters (Ea, ΔH#, ΔS# and ΔG#) have been evaluated. Kinetic studies show that the redox reaction between MnO2 and Gly-Leu proceeds through a mechanism combining one- and two-electron pathways: Mn(IV)→Mn(III)→Mn(II) and Mn(IV)→Mn(II). On the basis of the observed results, a possible mechanism has been proposed and discussed.

Oxidative degradation of dipeptide (glycyl–glycine) by water-soluble colloidal manganese dioxide in the aqueous and micellar media

The kinetics of the oxidative degradation of dipeptide glycyl–glycine (Gly-Gly) by water-soluble colloidal MnO 2 in acidic medium has been studied by employing visible spectrophotometer in the aqueous and micellar media at 35 °C. To obtain the rate constants as functions of [Gly-Gly], [MnO 2] and [HClO 4], pseudo-first-order conditions were maintained in each kinetic run. The first-order-rate is observed with respect to [MnO 2], whereas fractional-order-rates are determined in both [Gly-Gly] and [HClO 4]. The addition of sodium pyrophosphate and sodium fluoride has composite effects (catalytic and inhibition). The reaction proceeds through the fast adsorption of Gly-Gly on the surface of the colloidal MnO 2. The observed results are discussed in terms of Michaelis–Menten/Langmuir–Hinshelwood model. The Arrhenius and Eyring equations are found valid for the reaction over a range of temperatures and different activation parameters have been evaluated. A probable reaction mechanism, in agreement with the observed kinetic results, has been proposed and discussed. The influence of changes in the surfactant concentrations on the observed rate constant is also investigated and the reaction followed the same type of kinetic behavior in micellar media. The pseudo-first-order rate constant ( k ψ) is found to increase about two-fold with increase in [TX-100]. The catalytic effect of nonionic surfactant TX-100 is explained in terms of the mathematical model proposed by Tuncay et al.

Microemulsions with Surfactant TX100, Cyclohexane, and an Ionic Liquid Investigated by Conductance, DLS, FTIR Measurements, and Study of Solvent and Rotational Relaxation within this Microemulsion

Room-temperature ionic liquids (RTILs), N,N,N-trimethyl-N-propyl ammonium bis(trifluoromethanesulfonyl) imide ([N(3111)][Tf(2)N]), were substituted for polar water and formed nonaqueous microemulsions with cyclohexane by the aid of nonionic surfactant TX-100. The phase behavior of the ternary system was investigated, and microregions of [N(3111)][Tf(2)N]-in-cyclohexane (IL/O), bicontinuous, and cyclohexane-in-[N(3111)][Tf(2)N] (O/IL) were identified by traditional electrical conductivity measurements. Dynamic light scattering (DLS) revealed the formation of the IL microemulsions. The FTIR study of O-H stretching band of TX100 also supports this finding. The dynamics of solvent and rotational relaxation have been investigated in [N(3111)][Tf(2)N]/TX100/cyclohexane microemulsions using steady-state and time-resolved fluorescence spectroscopy as a tool and coumarin 480 (C-480) as a fluorescence probe. The size of the microemulsions increases with gradual addition of [N(3111)][Tf(2)N], which revealed from DLS measurement. This leads to the faster collective motions of cation and anions of [N(3111)][Tf(2)N], which contributes to faster solvent relaxation in microemulsions.

Water-soluble colloidal manganese dioxide as an oxidant for l-tyrosine in the absence and presence of non-ionic surfactant TX-100

Water-soluble colloidal manganese dioxide has been used to oxidize l-tyrosine in aqueous-acidic medium. The kinetics of the reaction was studied in the absence and presence of non-ionic surfactant (TX-100) using a spectrophotometric technique. As the reaction was fast under pseudo-first-order conditions ([ l-tyrosine] ≫ [MnO 2]), the rate constants as a function of [ l-tyrosine], [MnO 2], [HClO 4] and temperature were obtained under second-order conditions. The rate of the reaction increased and decreased with the increase in [ l-tyrosine] and [MnO 2], respectively. Perchloric acid, sodium pyrophosphate and sodium fluoride showed catalytic effect. The effect of externally added manganese(II) sulphate is complex. It is not possible to predict the exact dependence of the rate constants on manganese(II) concentration, which has a series of reactions with other reactants. The reaction is inhibited by the non-ionic surfactant TX-100. Activation parameters have been evaluated using Arrhenius and Eyring equations. Based on observed kinetic results, a probable mechanism for the reaction has been proposed which corresponds to fast adsorption of the reductant and hydrogen ion on the surface of colloidal MnO 2 followed by one-step two-electron transfer rate limiting process.

Time-resolved small-angle neutron scattering as a lamellar phase evolves into a microemulsion

Time-resolved small-angle neutron scattering (SANS) was used to follow the formation of a microemulsion after rapid stopped-flow mixing of a lamellar phase (Lα), comprising the non-ionic surfactant TX-100 and water, with toluene. Initially after mixing, an oil-swollen Lα phase was formed. Between 4 and 160 s the Lα system evolved into a dense water-in-oil (w/o) microemulsion, during which time the two phases coexisted. After 160 s, the system was a pure single-phase microemulsion. SANS spectra were fitted using a linear combination of the phenomenological Teubner–Stey microemulsion and the Nallet lamellar models. The characteristic repeat distance of water domains in the microemulsion was seen to decrease over the first 70 s of the transformation as more of the microemulsion formed; conversely the domain correlation length appeared to increase.