Glycol Dodecyl Ether Research Articles

Self-assembly of mixed surfactants sodium dodecylsulfate and polyethylene glycol dodecyl ether in aqueous solutions

The thermodynamic behavior of mixed systems containing the anionic surfactant sodium dodecyl sulfate (SDS) and the nonionic surfactant polyethylene glycol dodecyl ether (Brij L4) in aqueous solutions was investigated. Electrical conductivity and interfacial tension measurements were employed to investigate the concentration-dependent properties of these surfactant mixtures. Two main experiments were conducted: i) constant ratio experiment: the overall surfactant concentration was varied while maintaining a fixed ratio between SDS and Brij L4. It was shown that the critical micelle concentration (CMC) determined from electrical conductivity measurements does not indicate the formation of the first mixed micelles as observed using tensiometry, but the point from which the adsorption of counterions by the existing micelles became important. By using the Regular Solution Theory (RST), it was found that the interaction between SDS and Brij L4 is synergistic, driven by dipole-ion interactions of the hydrophilic regions of the two surfactants. ii) Fixed SDS concentration while increase the Brij L4 concentration: the resulting electrical conductivity exhibited non-trivial behavior which complexity arose from simultaneous phenomena of incorporation of free SDS molecules into the micelles as Brij L4 concentration increased, leading to a decrease in electrical conductivity; liberation of some adsorbed counterions from the mixed micelles to the solution, which increases the conductivity and increase of viscosity due to Brij L4 further addition that leads to a sequential decrease in electrical conductivity.

Well-dispersed graphene toward robust lubrication via reorganization of sliding interface

Excellent lubrication performance of graphene lubricant is mostly attributed to the dispersion of graphene and forming of tribo-film. Herein, diethylene glycol dodecyl ether (E2C12) functionalized graphene oxide (E2C12-GO) was successfully prepared by simple esterification. The physicochemical properties of as-prepared samples were characterized by a series of characterization methods. E2C12-GO with flat edge and high-level spacing possesses high dispersion stability in PAO 20 base oil. Compared with base oil, 0.08 wt% E2C12-GO could achieve the reduction of average friction coefficient and wear rate by 30 % and 57 % at 150 N, respectively. Even with each long-term friction, E2C12-GO could still maintain the state of robust low friction coefficient. Meanwhile, the addition of E2C12-GO can significantly improve the load-bearing capacity (PB value and PD value) of base oil. The excellent tribological properties of E2C12-GO were attributed to high dispersion and high layer spacing, as well as the reorganization of sliding interface. Prospectively, the E2C12-GO shows promising potential as a multi-functional oil-based lubricating additive in industrial applications.

Polyethylene Glycol Dodecyl Ether as Interfacial Modifier for Improving Efficiency of Perovskite Solar Cells

The rapid development of the perovskite solar cell (PSC) makes its best research efficiency comparable with that of silicon solar cells. However, the large‐scale application of PSCs still faces the dual challenges of improving efficiency and stability. Herein, an interfacial modifier of polyethylene glycol dodecyl ether (Brij) with ether group (C–O–C) and long alkyl chain is introduced into the interface of the perovskite layer and hole transport layer. It is demonstrated that the interaction of the ether group on Brij with uncoordinated lead ions on the perovskite passivates the point defects and reduces carrier recombination. The introduction of Brij tunes the energy gradient among electron transport layer/perovskite layer/hole transport layer and promotes the carrier extraction and transportation. The long alkyl chain of Brij covers the surface of perovskite and effectively improves the moisture resistance of perovskite films and the environmental stability of devices. Under an optimal Brij concentration, the modified perovskite solar cell achieves the best power conversion efficiency of 22.57%, along with improved environmental stability, while the pristine device obtains an efficiency of 20.66%.

Adsorption process and mechanisms of AEO-3/dodecane mixed collector on low-rank coal surface driven by water flow: A non-equilibrium molecular dynamics simulation study

During coal slime flotation, the collector is adsorbed to the coal in the form of fine oil droplets in the turbulent slurry. And understanding the adsorption behavior of collector oil droplets on the coal surface is important for the development of efficient collector. In this study, the adsorption process and mechanism of triethylene glycol dodecyl ether (AEO-311triethylene glycol dodecyl ether.)/dodecane mixed collector oil droplet (MCOD22mixed collector oil droplet.) on the surface of low-rank coal driven by water flow were investigated by non-equilibrium molecular dynamics simulations. The changes of the mass center velocity of MCOD, contact area and interaction energy between MCOD and coal during the simulation were analyzed, and the adsorption process was divided into the adhesion stage, spreading stage and equilibrium stage. The kinetic reason for the adsorption of AEO-3 molecules at the interface was found. The pushing of oil droplet by the water flow caused the AEO-3 molecules to be slowly pressed into the contact interface between the oil droplet and coal, and the adsorption occurred. The presence of polar oxygen-containing functional groups on the AEO-3 molecule makes it much more strongly adsorbed on low-rank coal than dodecane. Water molecules play an important role in the adsorption process of AEO-3 with coal, and the bridging action of water molecules that enables indirect adsorption of collector with coal was proposed. The water molecule connects AEO-3 and coal molecules, which cannot form hydrogen bond due to the distance, through hydrogen bonding, and inserts between alcohol oxygen, ether oxygen and carbonyl oxygen, which are originally mutually exclusive, so that the three of them (OAEO-3, H2O and Ocoal) are connected together through hydrogen bonding (OAEO-3…H-O-H…Ocoal), and the stability of AEO-3 adsorption on coal surface is greatly enhanced. The presence of strong indirect electrostatic interactions between polar collector and coal generated by the bridging action of water molecules proves that it is the strong electrostatic interactions that are the reason for the strong flotation performance of polar collector on low-rank/oxidized coals.

Ferrihydrite nanoparticles entrapped in shear-induced multilamellar vesicles

HypothesisFerrihydrite (Fh) nanoparticles are receiving considerable scientific interest due to their large reactive surface areas, crystalline structures, and nanoparticle morphology. They are of great importance in biogeochemical processes and have the ability to sequester hazardous and toxic substances. Here, the working hypothesis was to entrap fractal-like Fh nanoparticles, with a radius of gyration of 6.2 nm and a primary building block of polydisperse spheres with a radius of 0.8 nm, in a shear-induced multilamellar vesicle (MLV) state using a 40 wt% polyethylene glycol dodecyl ether surfactant. ExperimentsSmall- and Wide- Angle X-ray scattering revealed the equilibrium state of the non-ionic planar lamellar phase, the Fh dispersion, and their mixture. The MLV state was induced by using a shear flow in a Taylor-Couette geometry of a rheometer. FindingsThe nonionic surfactant initially exhibited a lamellar gel phase with two distinct d-spacings of 11.0 and 9.7 nm, which collapsed into the MLV state under shear flow. The Fh nanoparticles induced bilayer attraction by suppressing lamellar layer undulations, decreasing the d-spacing. These results are helpful in the understanding of the relationship between nanoparticle size and nanoparticle-bilayers interactions and provides insight on Fh encapsulations in a kinetically stable MLVs state.

A case study on the partitioning of pharmaceutical compound naproxen in edible oil-water system in the presence of ionic and non-ionic surfactants

The partitioning coefficient is a physicochemical quantity which gives important information about the distribution and efficiency of bioactive compounds in various biological systems. The present work aims at detailed investigation of the partition process of drug naproxen between edible oils (olive, sunflower, sesame) and water in the presence of two differently charged surfactants consisting of SDS (sodium dodecylsulfate), DTAB (n-dodecyltrimethylammonium bromide) and non-ionic surfactant Brij 35 (polyethylene glycol dodecyl ether). The evaluation was done at atmospheric pressure and 25.0 °C by using UV–Vis spectrometric and shake-flask techniques. In this work, all the surfactants are used in a concentration below their CMC due to the turbidity that occurs in the biphasic oil-water systems in the concentrations above their CMC. The experimental results obtained indicate that the oil-water partition coefficient (Koil/w) of naproxen reduce with rising the surfactants concentration in medium irrespective of the oil employed. Moreover, these values in the surfactant media are lower in comparison with surfactant free medium. The values of standard Gibbs free energy of the transfer (ΔGw→oil∘) calculated for all binary oil-water systems have negative sign which indicates the preference of this drug for oil phase and thus spontaneous partitioning process. The surfactant effect on the partition coefficients of drug is analyzed in terms of the intermolecular interactions such as hydrogen bonding, dispersion and electrostatic forces between the drug and the surfactant.

Lipid Scrambling Induced by Membrane-Active Substances

The functional roles of the lipid asymmetry of biomembranes are attracting increasing attention. This study characterizes the activity of surfactants to induce transmembrane flip-flop of lipids and thus “scramble” this asymmetry. Detergent-induced lipid scrambling of liposomes mimicking the charge asymmetry of bacterial membranes with 20 mol % of 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-rac-glycerol in the outer leaflet only was quantified by ζ-potential measurements for octaethylene glycol dodecyl ether (C12EO8), octyl glucoside (OG), and dodecyl maltoside. Membrane leakage was separately measured by the fluorescence lifetime-based calcein leakage assay and the onset of the membrane-to-micelle transition by isothermal titration calorimetry. Partition coefficients and partial molar areas were obtained as well. For the quickly membrane-permeant C12EO8 and OG, leakage proceeds at a rather sharp threshold content in the membrane, which is well below the onset of solubilization and little dependent on incubation time; it is accompanied by fast lipid scrambling. However, unlike leakage, flip-flop is a relaxation process that speeds up gradually from taking weeks in the detergent-free membrane to minutes or less in the leaking membrane. Hence, after 24 h of incubation, 10 mol % of C12EO8 or 50 mol % of OG in the membrane suffice for virtually complete lipid scrambling, whereas leakage remains below 10% for up to 14 mol % of C12EO8 and 88 mol % of OG. There is thus a concentration window in which lipid scrambling proceeds without leakage. This implies that lipid scrambling must be considered a possible mode of action of antimicrobial peptides and other membrane-active drugs or biomolecules. A related, detergent-based protocol for scrambling the lipid asymmetry of liposomes and maybe cells without compromising their overall integrity would be a very valuable tool to study functions of lipid asymmetry.

Highly efficient degradation of 2,2′,4,4′-tetrabromodiphenyl ether through combining surfactant-assisted Zn0 reduction with subsequent Fenton oxidation

2,2′,4,4′-tetrabromodiphenyl ether (BDE47) was difficult to be rapidly degraded by common reductive debromination or oxidative decomposition. In this study, the debromination via surfactant-assisted zero valent zinc (Zn0) reduction and subsequent Fenton oxidation was combined to completely degrade BDE47. Firstly, Zn0 integrated with surfactants including cetyltrimethylammonium chloride (CTAC), polyethylene glycol dodecyl ether (Brij35), or 1-dodecanesulfonic acid sodium salt (SDS) were evaluated for their reactivity to debrominate BDE47. CTAC-assisted Zn0 system presented the highest removal efficiency of 98.6% for BDE47 (C0 = 5 mg/L) under the optimized conditions including 0.3 g/L of Zn0 particles and 0.05 g/L of CTAC at 25 °C and pH 4.0 during 1-h reaction. Subsequently, the debromination products as low-brominated BDEs were attacked by hydroxyl radicals (•OH) from Fenton reagent, which were decomposed into short-chain carboxylic acids and even mineralized within 2-h oxidation. In addition, HPLC, GC–MS, LC–MS/MS, and IC were employed to detect intermediates during this reaction/oxidation process and the pathways of debromination and oxidation were proposed according to carbon and bromine balance. The above combination achieved the complete degradation of BDE47 via a relative low-cost method to rapidly remove PBDEs, which provide a new approach for the effective treatment of halogenated organic pollutants.

One-Pot Method for Preparation of Magnetic Multi-Core Nanocarriers for Drug Delivery.

The development of various magnetically-responsive nanostructures is of great importance in biomedicine. The controlled assembly of many small superparamagnetic nanocrystals into large multi-core clusters is needed for effective magnetic drug delivery. Here, we present a novel one-pot method for the preparation of multi-core clusters for drug delivery (i.e., magnetic nanocarriers). The method is based on hot homogenization of a hydrophobic phase containing a nonpolar surfactant into an aqueous phase, using ultrasonication. The solvent-free hydrophobic phase that contained tetradecan-1-ol, γ-Fe2O3 nanocrystals, orlistat, and surfactant was dispersed into a warm aqueous surfactant solution, with the formation of small droplets. Then, a pre-cooled aqueous phase was added for rapid cooling and the formation of solid magnetic nanocarriers. Two different nonpolar surfactants, polyethylene glycol dodecyl ether (B4) and our own N1,N1-dimethyl-N2-(tricosan-12-yl)ethane-1,2-diamine (SP11), were investigated for the preparation of MC-B4 and MC-SP11 magnetic nanocarriers, respectively. The nanocarriers formed were of spherical shape, with mean hydrodynamic sizes <160 nm, good colloidal stability, and high drug loading (7.65 wt.%). The MC-B4 nanocarriers showed prolonged drug release, while no drug release was seen for the MC-SP11 nanocarriers over the same time frame. Thus, the selection of a nonpolar surfactant for preparation of magnetic nanocarriers is crucial to enable drug release from nanocarrier.

Understanding of the foam capability of sugar-based nonionic surfactant from molecular level

In this paper, the correlation of the interfacial molecular array behavior of sugar-based green surfactant dodecyl maltoside DDM, and its apparent foam properties was investigated by molecular dynamics simulation and quantum chemical calculation as well as experimental methods. A common nonionic surfactant nona-ethylene glycol dodecyl ether C12E9, which has same hydrophobic tail and similar O atom number in headgroup with DDM, was studied as a reference. It was found that, not only the array behaviors of hydrophilic groups of DDM and C12E9 at the air-water interface, but also the intermolecular interactions were quite different. The simulation finding agreed well with the experimental results, by which how the interfacial molecular array behavior of the two types of nonionic surfactants affect the foam properties was revealed, and the application potential of DDM being used as foam stabilizer under diverse harsh conditions, such as high salinity, high temperature, strong acid and alkali, was presented, which should be quite meaningful.

An insight into effect of micelle-forming surfactants on aqueous solubilization and octanol/water partition coefficient of the drugs gemfibrozil and ibuprofen

Aqueous micellar solubilization of ibuprofen and gemfibrozil drugs was investigated at constant temperature (25.0±0.1) °C and atmospheric pressure using shake-flask and UV–vis spectrophotometric techniques. The solubility measurement was done in presence of three surfactants possessing different head groups, namely sodium dodecylsulfate (anionic SDS), cethyltrimethylammonium bromide (cationic CTAB) and polyethylene glycol dodecyl ether (non-ionic Brij 35) as well as their binary mixtures. The micellar solubility descriptors of χ (molar solubilization capacity), K (micelle–water partition coefficient), and ΔGs∘ (standard free energy of solubilization) were obtained to estimate quantitatively the solubilization efficiency of the surfactant systems. Moreover, the octanol-water partition coefficient of these drugs was also evaluated in the micellar solutions. The results obtained in the aqueous micellar system demonstrate that, irrespective of the surfactant type, the solubility of drugs increases with increasing the concentration of micelles. It was found that the solubility of ibuprofen and gemfibrozil in Brij 35 and CTAB solutions, respectively is higher compared to that in the other surfactants. However, the partition coefficients of these drugs show an inverse trend with solubility data. Finally, the effect of the surfactant type on solubility enhancement of the drugs is explained in terms of possible interactions between the drug and the micelle.

Cesium-substituted mesoporous phosphotungstic acid embedded chitosan hybrid polymer membrane for direct methanol fuel cells

Non-ionic polyethylene glycol dodecyl ether (Brij 76) template novel single-step process is successfully evolved for preparation of mesoporous cesium salt of phosphotungstic acid (PTA) with tunable porosity. Hybrid proton exchange membranes are prepared by embedding mesoporous cesium salt of PTA into chitosan (CS) polymer and are characterized by FTIR, TGA, and SEM mapping studies. To elucidate advantages of mesoporous structure, a series of CS hybrid membranes comprising non-porous cesium salt of phosphotungstic acid is also prepared and their functional properties are compared with mesoporous counterparts. Mesoporous nature helps to integrate membrane network creating maximum intermolecular interaction between organic and inorganic components. Both selective water sorption feature of CS and highly hydrophilic nature of mesoporous cesium salt of PTA together play a vital role in selective proton transport process through CS/m-PTA hybrid membranes. At optimal loading of m-PTA, maximum peak power density of 83 mW cm−2 was achievable with 2 M methanol as a fuel feed. On the basis of thermal stability, low methanol crossover, and appropriate proton conductivity, CS/m-PTA-5 wt% hybrid membrane could be proposed as novel polyelectrolytes for direct methanol fuel cell.

Effect of interlamellar interactions on shear induced multilamellar vesicle formation.

Shear-induced multilamellar vesicle (MLV) formation has been studied by coupling the small-angle neutron scattering (SANS) technique with neutron spin echo (NSE) spectroscopy. A 10% mass fraction of the nonionic surfactant pentaethylene glycol dodecyl ether (C12E5) in water was selected as a model system for studying weak inter-lamellar interactions. These interactions are controlled either by adding an anionic surfactant, sodium dodecyl sulfate, or an antagonistic salt, rubidium tetraphenylborate. Increasing the charge density in the bilayer induces an enhanced ordering of the lamellar structure. The charge density dependence of the membrane bending modulus was determined by NSE and showed an increasing trend with charge. This behavior is well explained by a classical theoretical model. By considering the Caillé parameters calculated from the SANS data, the layer compressibility modulus B¯ is estimated and the nature of the dominant inter-lamellar interaction is determined. Shear flow induces MLV formation around a shear rate of 10 s-1, when a small amount of charge is included in the membrane. The flow-induced layer undulations are in-phase between neighboring layers when the inter-lamellar interaction is sufficiently strong. Under these conditions, MLV formation can occur without significantly changing the inter-lamellar spacing. On the other hand, in the case of weak inter-lamellar interactions, the flow-induced undulations are not in-phase, and greater steric repulsion leads to an increase in the inter-lamellar spacing with shear rate. In this case, MLV formation occurs as the amplitude of the undulations gets larger and the steric interaction leads to in-phase undulations between neighboring membranes.

Determination of sub-ng g–1 levels of total inorganic arsenic and selenium in foods by hydride-generation atomic absorption spectrometry after pre-concentration

ABSTRACTA new and simple ultrasonic-assisted extraction (UAE) procedure was developed for the determination of inorganic arsenic and selenium in foods by hydride-generation atomic absorption spectrometry (HG-AAS). The various analytical variables affecting complex formation and extraction efficiency were investigated and optimised. The method is based on selective complex formation of As(III) and Se(IV) in the presence of excess As(V) and Se(VI) with toluidine red in the presence of tartaric acid at pH 4.5, and then extraction of the resulting condensation products into the micellar phase of non-ionic surfactant, polyethylene glycol dodecyl ether, Brij 35. Under optimised conditions, good linear relationships were obtained in the ranges of 4–225 and 12–400 ng l–1 with limits of detection of 1.1 and 3.5 ng l–1 for As(III) and Se(IV), respectively. The repeatability was better than 3.9% for both analytes (n = 10, 25 ng l–1) while reproducibility ranged from 4.2% to 4.8%. The recoveries of As(III) and Se(IV) spiked at 25–100 ng l–1 were in the range of 94.2–104.8%. After pre-concentration of a 5.0 ml sample, the sensitivity enhancement factors for As(III) and Se(IV) were 185 and 140, respectively. Accuracy was assessed by analysis of two standard reference materials (SRMs) and spiked recovery experiments. The method was successfully applied to the accurate and reliable determination of total As and total Se by HG-AAS after pre-reduction with a mixture of L-cysteine and tartaric acid. Finally, the method was shown to be rapid and sensitive, with good results for extraction, pre-concentration and determination of total As and Se contents (as As(III) and Se(IV)) from food samples.

A New Ultrasonic Thermostatic-Assisted Cloud Point Extraction/Spectrophotometric Method for the Preconcentration and Determination of Bisphenol A in Food, Milk, and Water Samples in Contact with Plastic Products

Bisphenol A (BPA) contamination in foods and beverages usually occurs as a result of migration from the packages that contain it. In this context, a simple, easy-to-use, and efficient method was developed for the spectrophotometric determination of BPA in food, milk, and water samples in contact with plastic products after preconcentration by ultrasonic-thermostatic-assisted cloud point extraction (UTA-CPE). The method is based on the charge transfer-sensitive complexation of BPA with 3-methylamino-7-dimethylaminophenothiazin-5-ium chloride (AzB) in the presence of cetyltrimethylammonium bromide (CTAB) at pH 8.5 and then extraction of the formed complex into the micellar phase of polyethylene glycol dodecyl ether (Brij 35). The effects of the analytical variables affecting complex formation and extraction efficiency were systematically studied and optimized. Under optimized conditions, a good linear relationship was obtained in the range of 1.2–160 μg L−1 with a detection limit of 0.35 μg L−1. After preconcentration of a sample of 20 mL, a sensitivity enhancement factor was found to be 180. The accuracy and reliability of the method were evaluated by recovery studies from the spiked quality control samples and intraday and interday precision studies. From the studies conducted, the extraction efficiency (E%) was in the range of 94–103% with a relative standard deviation lower than 5.2% (as RSD%, n = 5). The method was successfully applied to the preconcentration and determination of BPA from the selected sample matrices.

Critical thickness of foam films stabilized by nonionic or ionic surfactants and their mixtures

The critical thickness (hcr) for foam films of n-dodecyl β-D maltoside (C12G2) and of its mixed solutions with dodecanol (C12Е0), hexaethylene glycol dodecyl ether (C12E6) and dodecyl trimethylammonium bromide (C12TAB) of different molar ratios (50:1; 1:1;1:50) at low and high ionic strength was measured interferometrically. It was found that hcr increases with an increase in the film radius, regardless of the solution’s composition. At low ionic strength the type of surfactant influences substantially the value of hcr. At high ionic strength the level of nonionic surfactant does not in fact influence the value of the critical thickness, while the effect of an ionic surfactant may be significant, in accord with its molar ratio in the mixture: (i) C12TAB in the 50:1 molar ratio mixture acts as a minor additive and supports C12G2 in reducing of negative charge; the values of hcr for films from the mixture are lower than those from solution of C12G2 alone; (ii) at a molar ratio 1:1C12TAB has a dominant role, so it recharges the film surfaces and the hcr values of films from the mixture are higher.The measured critical thicknesses hcr(exp) have been juxtaposed with the calculated ones hcr (cal) by the approaches of Vrij, Radoev-Scheludko-Manev (RShM) and Coons. In two of the cases, the experimentally determined drainage coefficient α has been used. The comparison has shown that the combination of RShM equation with α firmly improves the correlation between hcr(exp) and hcr(cal). Good agreement between hcr(exp) and hcr(cal) for films of low surfaces coverage was achieved by introducing an additional, non-DLVO attraction force.

Investigation of suppressor polyethylene glycol dodecyl ether on electroplated Cu filling by electrochemical method

In this paper, the use of polyethylene glycol dodecyl ether (POE) with a molecular weight of 1200 (POE-1200) as a suppressor for bottom-up electroplated copper filling of microvias was investigated. Galvanostatic measurement indicated that POE-1200 had much stronger suppression for Cu electrodeposition than PEG-8000 (polyethylene glycol with a molecular weight of 8000) and EPE-8000 (triblock copolymers of ethylene oxide–propylene oxide–ethylene oxide with a molecular weight of 8000). The strong synergistic suppression between POE-1200 and Cl− led to a very thin surface thickness and excellent filling performance of microvias. The cross-sectional observations of the microvias after electroplated confirmed that changing the POE-1200 concentration from 20 to 700 ppm had little effect on the filling performance because of an unchanged positive potential difference. The adsorption strength of POE-1200 on the cathode surface was enhanced greatly only in the presence of Cl− , attributing to a formation of Cl− –Cu+–POE-1200 complex. The critical adsorption concentration of Cl− and POE-1200 to form a saturated barrier film on the electrode surface was studied by Cu stripping peaks of cyclic voltammetry curves. In addition, the relationship between the saturated barrier of Cl− –Cu+–POE-1200 complex and the filling performance has been proposed.

Solubilization of Phenanthrene and Fluorene in Equimolar Binary Mixtures of Gemini/Conventional Surfactants

This study deals with the enhanced solubilization of polycyclic aromatic hydrocarbons (PAHs) such as phenanthrene (PHE) and fluorene (FLR) in a pure cationic gemini (G6) and three conventional surfactants [polyethylene glycol dodecyl ether (Brij35), cetyltrimethyl ammonium bromide (CTAB) and sodium lauryl sulfate (SDS)] as well as in their equimolar binary combinations (G6-Brij35, G6-CTAB and G6-SDS). Their solubilization efficiency toward PHE and FLR has been quantified in terms of the molar solubilization ratio (MSR) and the micelle–water partition coefficient (Km). The ideality/nonideality of the mixed micelles is discussed with the help of Clint, Rubingh and Rosen's approaches. These theories determine the deviation of experimental critical micelle concentration (CMC) values from ideal critical micelle concentration, which was measured by evaluating the interaction parameters (βm and βσ). Negative values of βm were observed in all the equimolar binary systems, which show synergism in the mixed micelles. Whereas at air/liquid interface synergism was observed in the systems G6-CTAB and G6-Brij35; G6-SDS exhibited an antagonistic effect. The order of MSR and Km was G6-CTAB>G6-Brij35>G6-SDS for phenanthrene as well as for fluorene.

Solubilization in Mixed Micelles Studied by Molecular Dynamics Simulations and COSMOmic

Up to now, micelles composed of different surfactants (mixed micelles) are rarely studied with molecular methods. This is in contrast to their importance for pharmaceutical or industrial applications, where it is of great interest to predict the partition behavior for a large set of solutes (screening) within mixed micelles. This work is focused on molecular simulations of phase equilibria in mixed surfactant systems, because mixtures of different types of surfactants (nonionic or ionic) in aqueous solution can change the partition behavior of solutes tremendously. The extension of COSMO-RS for anisotropic phases, named COSMOmic, is computationally efficient and can be used as a screening tool for finding adequate surfactant systems for a specific extraction task. However, it needs micellar structures as an input. Therefore, molecular dynamics (MD) simulations of the self-assembly of pure Brij35 (polyethylene glycol dodecyl ether) and mixtures either with CTAB (cetyltrimethyl ammonium bromide) or SDS (sodium dodecyl sulfate) at different concentrations are performed. The micelles from the self-assembly MD simulations are used to predict the partition behavior of various solutes between micelle and bulk water with COSMOmic. In this way, various micelles of different size and composition are investigated and structural influences on partition equilibria of solute molecules like ephedrine, acetone, toluene, coumarin, isovanillin, ferulic acid, vanillic acid, syringic acid, and phenol are analyzed. For the first time, the self-assembly of pure Brij35 and the mixtures of Brij35/CTAB and Brij35/SDS is studied on an atomistic scale. Significant influences of atomic structure and composition of mixed micelles on partition equilibria are elucidated. The findings of this detailed analysis are in good agreement with experimental data and likely to improve the knowledge and understanding of mixed micellar extraction processes and can pave the way for more practical applications in the future.

Dynamic Phase Diagram of a Nonionic Surfactant Lamellar Phase

The dynamic phase diagram of triethylene glycol dodecyl ether (C12E3) in D2O was determined for 40, 50, and 60 wt % of surfactant. The shear flow effect on the nonionic lamellar phase was investigated as a function of temperature and concentration. The transition from planar lamellae (Lα)-to-multilamellar vesicles (MLVs) was characterized by means of rheology, rheo-small-angle neutron and light scattering. New insight into the nature of the transition region between Lα and the MLVs state is provided. A disorder-order transition was also observed by SANS. This is attributed to a transition from disordered MLVs to a close-packed array of MLV's with slightly higher order than before. Moreover flow instability was observed in the shear-thickening regime at 40 °C.