Range Of Surfactant Concentrations Research Articles

Erratum: High-Throughput Identification of Resistance to Pseudomonas syringae pv. Tomato in Tomato using Seedling Flood Assay.

Erratum: High-Throughput Identification of Resistance to Pseudomonas syringae pv. Tomato in Tomato using Seedling Flood Assay.

Sequential Demulsification through the Hydrophobic-Hydrophilic-Hydrophobic Filtration Layer toward High-Performing Oil Recovery.

Demulsification using membranes is a promising method to coalesce highly stable emulsified oil droplets for oil recovery. Nevertheless, a structure of the current filtration medium that is not efficient for oil droplet coalescence impedes rapid permeability, thereby inevitably restricting their practical applications. Herein, we report a hydrophobic-hydrophilic-hydrophobic (3H) demulsification medium that exhibits a benchmark permeability of ∼2.1 × 104 L m-2 h-1 with a demulsification efficiency of >98.0%. Remarkably, this 3H demulsification medium maintains over 90% demulsification efficiency in the oil-in-water (O/W) emulsions with a wide range of surfactant concentrations, which shows excellent applicability. Based on the combined results of quasi situ microscope images and molecular dynamics simulations, we show that the polydimethylsiloxane-modified hydrophobic layer facilitates the capture and coalescence of oil droplets, the hydrophilic inner layer assists in squeezing the coalescence of enlarged droplets, and the third hydrophobic layer accelerates the discharge of demulsified oil to sustain permeability. The sequential demulsification mechanism between this 3H filtration layer provides a general guide for designing a demulsifying membrane with high demulsification efficiency and high flux toward oil recovery.

The role of surface tension on the growth of bubbles by rectified diffusion

Rectified diffusion has wide and important applications in sonochemistry, ultrasonic cleaning and medical ultrasound. Recent experimental results have demonstrated that the addition of surfactant substantially enhances bubble growth rate. As a hypothesis, this was widely attributed to the acoustic microstreaming and mass transfer resistance caused by surfactants. In this research, the effects of the surfactant of sodium dodecyl sulphate on the rectification have been simulated by considering only the variation of the surface tension coefficient due to the surfactant. The computations are carried out using a newly developed tractable model based on the multi-scale method and the method of matched asymptotic expansions, which allows the prediction of bubble growth taking place over millions of oscillation cycles. The rate of bubble growth observed in the experiments is accurately predicted by our computations, for a range for bulk surfactant SDS concentrations less than or equal to 2.4 mM. Contrary to the widely held hypothesis in the published literature, this has demonstrated that the dominant physical mechanisms remain the shell and area effects in this range of bulk surfactant concentrations. The further enhancement of bubble growth rate provided by either acoustic microstreaming or the resistance to mass transfer is only evident at higher bulk surfactant concentrations. Therefore, the role of surface tension in rectified diffusion for aqueous surfactant solutions is more significant than previously understood. The new results also show that the bubble growth rate is sensitive to small changes in the bubble radius which may account for its unpredictability in applications of sonochemistry.

SLE3S-water system: a linear rheological characterisation

AbstractSurfactant-water mixtures display a complex rheological behaviour, with changes in parameters such as viscosity and moduli of several orders of magnitude as a consequence of phase changes, depending on their concentration and temperature: this criticism heavily affects different industrial processes. In our work, linear rheological behaviour of aqueous mixtures of a commercial anionic surfactant, sodium lauryl ether sulphate, is investigated in a range of temperature (30–60 °C) and surfactant concentration (20–72%wt) of technological relevance. Four phases with different texture are identified by polarised light microscopy: micellar, hexagonal, cubic and lamellar, all showing a shear-thinning behaviour. Rheological parameters of cubic phase show a net jump in a relatively narrow temperature range, suggesting a temperature-induced phase change. The systematic analysis of the rheological behaviour of this widely used surfactant system, reported here for the first time, can be of fundamental support for many industrial applications. Graphical Abstract

Hydroxyapatite nanoparticle-modified porous bone grafts with improved cell attachment.

Emulsion-templated foams have displayed promise as injectable bone grafts; however, the use of a surfactant as an emulsifier resulted in relatively small pores and impedes cell attachment. Hydroxyapatite nanoparticles were explored as an alternative stabilizer to address these limitations. To this end, hydroxyapatite nanoparticles were first modified with myristic acid to generate the appropriate balance of hydrophobicity to stabilize a water-in-oil emulsion of neopentyl glycol diacrylate and 1,4-butanedithiol. In situ surface modification of the resulting foam with hydroxyapatite was confirmed with elemental mapping and transmission electron microscopy. Nanoparticle-stabilized foams displayed improved human mesenchymal stem cell viability (91 ± 5%) over surfactant-stabilized foams (23 ± 11%). Although the pore size was appropriate for bone grafting applications (115 ± 71 μm), the foams lacked the interconnected architecture necessary for cell infiltration. We hypothesized that a co-stabilization approach with both surfactant and nanoparticles could be used to achieve interconnected pores while maintaining improved cell attachment and larger pore sizes. A range of hydroxyapatite nanoparticle and surfactant concentrations were investigated to determine the effects on microarchitecture and cell behavior. By balancing these interactions, a co-stabilized foam was identified that possessed large, interconnected pores (108 ± 67 μm) and improved cell viability and attachment. The co-stabilized foam was then evaluated as an injectable bone graft including network formation, microscale integration with bone, push out strength, and compressive properties. Overall, this work demonstrated that in situ surface modification with nHA improved cell attachment while retaining desirable bone grafting features and injectability.

Flow characteristics and regime transition of aqueous foams in porous media over a wide range of quality, velocity, and surfactant concentration

Aqueous foam is broadly applicable to enhanced oil recovery (EOR). The rheology of foam as a function of foam quality, gas and liquid velocities, and surfactant concentration constitute the foundation of its application. The great variations of the above factors can affect the effectiveness of N2 foam in EOR continuously in complex formations, which is rarely involved in previous relevant studies. This paper presents an experimental study of foam flow in porous media by injecting pre-generated N2 foam into a sand pack under the conditions of considering a wide range of gas and liquid velocities and surfactant concentrations. The results show that in a wide range of gas and liquid velocities, the pressure gradient contours are L-shaped near the coordinate axes, but V-shaped in other regions. And the surfactant concentration is a strong factor influencing the trend of pressure gradient contours. Foam flow resistance is very sensitive to the surfactant concentration in both the high- and low-foam quality regime, especially when the surfactant concentration is less than CMC. The foam quality is an important variable to the flow resistance obtained. There exists a transition point from low- to high-quality regime in a particular flow system, where has the maximum flow resistance, the corresponding foam quality is called transition foam quality, which increases as the surfactant concentration increases. The results can add to our knowledge base of foam rheology in porous media, and can provide a strong basis for the field application of foams.

Exploring drug-surfactant interactions and their impact on the intrinsic surface properties of aqueous dissolution media

Surfactants are often used to improve the solubility of a compound for dissolution studies in aqueous media. Having observed non-linear solubility enhancement with increasing surfactant concentration, this study investigated the effect of a poorly soluble, zwitterionic, moderately lipophilic drug, Compound A, on the critical micelle concentration (CMC)of sodium lauryl sulfate (SLS) in phosphate buffer. A force tensiometer was used to measure the surface tension of the solutions over a range of surfactant concentrations. The presence of Compound A demonstrated a decrease in the CMC, suggesting that the solution favours micellisation at lower surfactant concentrations in the presence of the drug. Future studies will use a fully saturated solution of Compound A to explore this observation further. Additional experiments will also investigate micelle formation of SLS with other compounds.

Alginic Acid Beads Containing Fluorescent Solvatochromic Dyes Display an Emission Color Response to a Cationic Surfactant.

Lipophilic fluorescent dyes can be employed as sensors for surfactants present in concentrations above the critical micellar concentration (CMC) where the dyes are monodispersed in micelles. However, the surfactant concentration range over which these dyes are effective is narrowed because by the sigmoidal nature of their responses. To overcome this limitation, we developed a novel sensor material comprised of a labeled fluorescent solvatochromic dye covalently bonded to alginate gel, which is known to strongly adsorb cationic surfactants. We hypothesized that the dye-alginate conjugate would undergo fluorescent color changes in response to binding of surfactants which alter the polarity of the surrounding environment. Indeed, addition of the representative cationic surfactant, cetylpyridinium chloride (CPC), to an aqueous solution of the alginate conjugated fluorescent solvatochromic dye leads to a visible fluorescent color change when the concentration of CPC is below the CMC. The average values of the color appearance parameter, referred to as a hue, of light emitted from gels, calculated by analysis of fluorescence microscopy images using ImageJ software, were found to be approximately linearly dependent on the concentration of CPC encapsulated in the alginate-fluorescent dye complex. This finding shows that absorbed CPC can be quantitatively determined over a wide concentration range in the form of simple fluorescence wavelength or visible responses.

Droplet microfluidics for studying surfactant-rich interfaces found in aerosols, emulsions and foams

<h2>Abstract</h2> The presence of droplets suspended in a liquid or gas is known to play an essential role in fields ranging from materials to atmospheric science. Often, the dispersed phase is stabilized by surface active compounds and surfactants, resulting in complex chemical composition and material properties at the fluid-fluid interface. In this talk, recent advancements in use of microscale flow fields will be highlighted for measuring properties of aqueous multiphase, interface-rich systems. Systems studied will include atmospheric aerosol droplets and liquid-liquid emulsions. Microfluidic contractions, traps, and wells are used to measure surface-bulk partitioning and temperature-dependent liquid-liquid phase separation of aqueous droplets, towards better understanding of suspensions of aerosol droplets in our atmosphere. Advanced measurements of droplet shape deformations and coalescence will also be presented for both water-in-fuel and oil-in-water emulsions, for improved treatment and separation of emulsions. Dynamic interfacial tensions measurements were performed using a microfluidic tensiometer, demonstrating a dependence on if the surfactant approaches the interface from inside (dispersed) versus outside (continuous), implying phase dependent surfactant transport to curved interfaces at the microscale. Droplet coalescence and film drainage experiments are also performed in a microfluidic Stokes trap across a range of viscosity ratios and surfactant concentrations. Results are used to explore the influence of interfacial mobility and Marangoni stresses on film stability with soluble surfactants.

Spectroscopic studies of the quercetin/rutin-nonionic surfactant interactions

• Interactions between Ru with TX114 and Q with T80 are strong. • Interactions is mostly based on hydrogen bonds and hydrophobic forces. • For Ru with TX114 there are the highest partition coefficient. The behaviour of quercetin (Q) and rutin (Ru) in the aqueous solution of two nonionic surfactants, Triton X-114 (TX114) and Tween 80 (T80) was investigated using the spectroscopic techniques. The object of investigations were the interactions between the given flavonoid and the surfactant in a wide range of surfactant concentrations and the temperature range from 293 to 313 K. The obtained UV–Visible and emission spectra were the basis for determination of the binding constant, partition coefficient, Gibbs free energy of binding as well as partition, enthalpy and entropy of binding and partition. It was proved that the interactions between Ru with TX114 and Q with T80 are strong and become weaker with the increasing temperature. The nature of interactions between the molecules is mostly based on the hydrogen bonds and hydrophobic forces.

Interaction between meso-tetra-(4-hydroxyphenyl)porphyrin and SDS in aqueous solutions: Premicellar porphyrin-surfactant J-aggregate formation

Interactions between meso-tetra(4-hydroxyphenyl)porphyrin (THPP) and anionic sodium n-dodecyl sulfate (SDS) in a wide surfactant concentration range (0.5–50 mM) have been studied by UV–vis absorption and fluorescence spectroscopy, resonance light scattering (RLS), spin probe EPR spectroscopy and dynamic light scattering (DLS). J-type aggregate formation has been observed for THPP within 2–5 mM surfactant concentration range, accompanied by a significant bathochromic shift of the absorption bands, fluorescence quenching and emergence of an intense RLS signal. Porphyrin binding to the surfactant micelles above the cmc and aggregate formation below the cmc have been observed in SDS solutions containing THPP by DLS and EPR spectroscopy. SEM and optical microscopy revealed a rod-like morphology of the microparticles crystallized from an air dried suspension of THPP J-aggregates. The results obtained contribute to understanding of the mechanism of porphyrin-surfactant interactions both below and above the surfactant cmc.

Dynamics of CTAB micelle mediated reaction of fuchsin degradation in alkaline medium

Abstract Cetyltrimethylammonium bromide (CTAB) micelles catalyzed the degradation of fuchsin in the entire surfactant concentration range investigated. The pseudo first order rate constants increased with CTAB concentrations. However, there was a decrease in the rate constant at higher concentrations of CTAB. Increase in the rate constant was attributed to the incorporation of fuchsin and hydroxide ion in the stern layer of the CTAB micelles. The kinetics involved the removal of the π-conjugation in fuchsin due to its attack by hydroxide ion on the central C atom of the planar ring which led to the formation of carbinol. The reaction showed first order each to fuchsin and OH-. Menger-Portnoy and Piszkiewicz cooperative models were used to explain the micellar and kinetic effects.

The Effect of Electrolytes and Urea on the Ethyl Lauroyl Arginate and Cellulose Nanocrystals Foam Stability

Carboxylated cellulose nanocrystals (cCNC) are highly dispersible particles useful in many industries. In particular, they can be applied to form Pickering emulsions and foams for “green” applications in the cosmetics, pharmaceutical industry or food processing. We demonstrated that carboxylated cellulose nanocrystals enhance foamability and foam stability when mixed with cationic surfactant ethyl lauroyl arginate (LAE), having superior properties over sulfated cellulose nanocrystals (sCNC) concerning surfactant concentration range and foam volume. Mixtures of LAE and cCNC were characterized for their hydrodynamic diameter, zeta potential, surface tension and surface rheological properties. The influence of electrolytes, namely, sodium chloride, guanidine hydrochloride and sodium salicylate, and the addition of concentrated urea to LAE-cCNC mixtures on foamability and foam stability were investigated. Electrolytes in the concentration of 5 mM showed a moderate effect on foam stability. In contrast, spectacular foam collapse was detected after adding concentrated urea. The preliminary rheological data from the pendant drop oscillations revealed low elastic modulus upon urea addition and the loss modulus that increased with the frequency, which suggested a viscous interfacial layer.

Preparation and Characterization of Lidocaine-Loaded, Microemulsion-Based Topical Gels.

Microemulsion-based gels (MBGs) were prepared for transdermal delivery of lidocaine and evaluated for their potential for local anesthesia. Lidocaine solubility was measured in various oils, and phase diagrams were constructed to map the concentration range of oil, surfactant, cosurfactant, and water for oil-in-water (o/w) microemulsion (ME) domains, employing the water titration method at different surfactant/cosurfactant weight ratios. Refractive index, electrical conductivity, droplet size, zeta potential, pH, viscosity, and stability of fluid o/w MEs were evaluated. Carbomer® 940 was incorporated into the fluid drug-loaded MEs as a gelling agent. Microemulsion-based gels were characterized for spreadability, pH, viscosity, and in-vitro drug release measurements, and based on the results obtained, the best MBGs were selected and subsequently subjected to ex-vivo rat skin permeation anesthetic effect and irritation studies. Data indicated the formation of nano-sized droplets of MEs ranging from 20 - 52 nm with a polydispersity of less than 0.5. In-vitro release and ex-vivo permeation studies on MBGs showed significantly higher drug release and permeation in comparison to the marketed topical gel. Developed MBG formulations demonstrated greater potential for transdermal delivery of lidocaine and advantage over the commercially available gel product, and therefore, they may be considered as potential vehicles for the topical delivery of lidocaine.

Fluorescence Study of the Interaction between Hydrophobically Modified Polymers and Charged Particles in Aqueous Media.

The interaction of hydrophobically randomly modified and end-modified poly(2-(acrylamido)-2-methylpropanesulfonate)s (PAMPSs) with nonionic and positively and negatively charged surfactants was studied with the fluorescence spectroscopic technique of labeled pyrene. The results indicated that the randomly modified PAMPS bound to the nonionic and positively charged surfactants and that the disruption of intrapolymer micelles formed by the polymer occurred. In contrast, end-modified PAMPS was bound to the surfactants without the disruption of multipolymer aggregates formed by the polymer in a comparably low concentration range of surfactants. The conformation of the polymer-surfactant complex was confirmed to depend on the position of the hydrophobic group in the polymer chains. In the case of negatively charged surfactant, the complex formation between the polymers and the surfactants was significantly restricted due to the electrostatic repulsion of anionic sites of the polymer chains and the negatively charged surfactants.

Formulation and Evaluation of Microemulsion of Curcumin in Thymol-Menthol Carrier System

Aim: To formulate and evaluate the Micro emulsion of curcumin in thymol-menthol carrier system.&#x0D; Study Design: Curcumin dissolves in mixture of thymol &amp; menthol to reasonable extent.100 mg of curcumin in 1 g of thymol and 0.6 g of menthol mixture was finalized as product mixture. The solution of curcumin in eutectic mixture being oily liquid, it gave the idea for development for the micro emulsion&#x0D; Place and Duration of Study: Department of Pharmaceutics and Department of Pharmacognosy, STES’s Smt. Kashibai Navale College of Pharmacy, Kondhwa (BK), National Chemical Laboratory, Pune between June 2016 and May 2017.&#x0D; Methodology: Micro emulsion system with eutectic mixture of thymol and menthol was chosen as oil phase and carrier for curcumin, tween 80 as surfactant and ethanol as co-surfactant. Ternary phase diagrams were constructed to obtain the optimum concentration range of oil phase, surfactant and co-surfactant. The micro emulsion of 100 mg curcumin containing 4.95 % oil phase, 33.39 % surfactant, 11.13% co-surfactant, 50:50% of water was optimum. Micro emulsion of curcumin was prepared by water titration method and evaluated for globule size, drug content, pH, viscosity, conductivity and In vitro drug release study. The ex-vivo permeation study for micro emulsion of curcumin was carried out on excised mice skin using Franz Diffusion apparatus. The cytotoxicity study for thymol, menthol was performed on healthy L929 murine fibroblast cell line. Anticancer activity of thymol-menthol eutectic mixture alone and with curcumin was performed on HeLa cell lines.&#x0D; Results: The preformulation studies did clearly indicate good compatibility of drug with thymol menthol carrier system. The cytotoxicity study was done on thymol – menthol(TM) as a preformulation aspect to ascertain the toxicity of these two excipients to be tried. It was found that TM was not cytotoxic in 120ug/mL concentration and thus was safe to be used in concentration below 120ug/mL. Batch B1 was optimised. The average globule size of micro emulsion was found to be 131.54 nm, zeta potential was found to be -0.57 mV. The drug content in micro emulsion batch B1 was determined and found to be 74.6%.Permeability study across mice skin ex-vivo model showed 52.38% permeability compared with curcumin alone which was 22.41%. So permeability of curcumin is enhanced substantially with micro emulsion made in thymol and menthol, owing to fact that thymol and menthol act as good permeation enhancers. The In vitro drug release study of micro emulsion was compared with curcumin alone. About 48.75% of curcumin was released from micro emulsion showed increase in release rate.&#x0D; Conclusion: Eutectic mixture of thymol and menthol showed promising results as penetration and solubility enhancer for curcumin. Solubility of curcumin was improved so as its rate of permeation which was used to develop formulation of micro emulsion with proven anticancer activity. The solubility of curcumin formulated with combination of eutectic mixture was increased up to 50 %.

Dual Transient Networks of Polymer and Micellar Chains: Structure and Viscoelastic Synergy.

Dual transient networks were prepared by mixing highly charged long wormlike micelles of surfactants with polysaccharide chains of hydroxypropyl guar above the entanglement concentration for each of the components. The wormlike micelles were composed of two oppositely charged surfactants potassium oleate and n-octyltrimethylammonium bromide with a large excess of anionic surfactant. The system is macroscopically homogeneous over a wide range of polymer and surfactant concentrations, which is attributed to a stabilizing effect of surfactants counterions that try to occupy as much volume as possible in order to gain in translational entropy. At the same time, by small-angle neutron scattering (SANS) combined with ultrasmall-angle neutron scattering (USANS), a microphase separation with the formation of polymer-rich and surfactant-rich domains was detected. Rheological studies in the linear viscoelastic regime revealed a synergistic 180-fold enhancement of viscosity and 65-fold increase of the longest relaxation time in comparison with the individual components. This effect was attributed to the local increase in concentration of both components trying to avoid contact with each other, which makes the micelles longer and increases the number of intermicellar and interpolymer entanglements. The enhanced rheological properties of this novel system based on industrially important polymer hold great potential for applications in personal care products, oil recovery and many other fields.

Interfacial Mass Transfer in Trichloroethylene/Surfactants/ Water Systems: Implications for Remediation Strategies

The fate of dense non-aqueous phase liquids (DNAPLs) in the environment and the consequential remediation problems have been intensively studied over the last 50 years. However, a scarce literature is present about the mass transfer at the DNAPL/water interface. In this paper, we present a fast method for the evaluation of the mass transfer performance of a surfactant that can easily be employed to support an effective choice for the so-called enhanced remediation strategies. We developed a lab-scale experimental system modelled by means of simple ordinary differential equations to calculate the mass transfer coefficient (K) of trichloroethylene, chosen as representative DNAPL, in the presence and in the absence of two ethoxylated alcohols belonging to the general class of Synperonic surfactants. Our findings revealed that it exists an optimal surfactant concentration range, where K increases up to 40% with respect to pure water.

Oil emulsion characteristics as significance in efficiency forecast of oil-displacing formulations based on surfactants

Enhanced oil recovery in mature fields can be implemented using chemical flooding with the addition of surfactants using surfactant-polymer (SP) or alkaline-surfactant-polymer (ASP) flooding. Chemical flooding design is implemented taking into account reservoir conditions and composition of reservoir fluids. The surfactant in the oil-displacing formulation allows changing the rock wettability, reducing the interfacial tension, increasing the capillary number, and forming an oil emulsion, which provides a significant increase in the efficiency of oil displacement. The article is devoted with a comprehensive study of the formed emulsion phase as a stage of laboratory selection of surfactant for SP or ASP composition. In this work, the influence of aqueous phase salinity level and the surfactant concentration in the displacing solution on the characteristics of the resulting emulsion was studied. It was shown that, according to the characteristics of the emulsion, it is possible to determine the area of optimal salinity and the range of surfactant concentrations that provide increased oil displacement. The data received show the possibility of predicting the area of effectiveness of ASP and SP formulations based on the characteristics of the resulting emulsion.

Neutron investigation of interaction between anionic surfactant micelles and poly (ethylene glycol) polymer brush system

A polymer brush system of a neutral polymer poly (ethylene glycol) with a molecular weight of Mw = 20 kDa on silicon substrates in an aqueous medium was studied by the specular neutron reflectometry. Structural changes in the density profile of a polymer brush caused by the interaction of polymer chains with micelles of the anionic surfactant dodecylbenzenesulfonate acid were observed. The effect is shown to be related to the formation of molecular polymer-micelle associates in the bulk of the solution, which was previously studied by small-angle neutron scattering in a wide range of surfactant concentrations at various molecular weights of the polymer. The density of the dry polymer layer on the silicon substrate was additionally characterized by X-ray reflectometry and scanning atomic force microscopy.