Anionic Surfactant Systems Research Articles

Effect of NaCl on the binding constant of styryl pyridinium dyes in anionic surfactant system

Perturbation of micelle structure by salt plays a vital role in micellar growth. Cationic alkyl styryl pyridinium dyes are found to interact differently with anionic surfactant systems according to their structural differences. In this work the binding constant of some tailor made styryl pyridinium dyes (1) in ground state and excited state has been studied in anionic sodium dodecyl sulfate (SDS) in the presence and absence of NaCl using absorption and steady state fluorescence spectroscopy. Larger binding constant of the dyes in the excited state compared to the ground state has been explained in terms of flexibility of dyes in excited state. The highest binding constant value for C12 is attributed to the compatibility of the hydrophobic chain of both the surfactant and the dye.

Modeling of Precipitation Phase Boundaries in Mixed Surfactant Systems Using an Improved Counterion Binding Model

AbstractAnionic surfactants, commonly used in household products and the detergency industry, tend to precipitate with divalent counterions in hard water. The unsightly soap scum thus formed also removes the surfactant from the cleaning action. The current research has improved prediction of the precipitation phase boundary for mixtures of surfactants in hard water in two ways: firstly, an accurate value of the solubility product (KSP) has been determined for the calcium salt of 4‐octylbenzene sulfonate, and accurate temperature dependent KSP values have been determined for the calcium salts of dodecyl sulfate and decyl sulfate; secondly, improvements in prediction of the precipitation phase boundary have been achieved using an improved model. The KSP values of the decyl sulfate and dodecyl sulfate salts strongly increase with increasing temperature, with the shorter chain surfactant having significantly higher KSP than its longer chain analogue. At 30 °C the KSP of the 4‐octylbenzenesulfonate salt is similar to that of the dodecyl sulfate salt, perhaps due to the similarity in the length of their hydrocarbon tails. A recent counterion binding model proposed by our research group and micellization models have been used to model the precipitation phase boundaries for both single anionic surfactant and binary mixed anionic surfactant systems, improving thermodynamic modeling of the precipitation phase boundary of single and binary mixed anionic surfactant systems. In particular, the improved model of counterion binding has allowed the model to predict the phase boundary accurately over a range of temperatures.

Energetics of anionic surfactant-additive systems at the cloud point

The energetics of clouding in anionic surfactant (SDBS) and tetrabutylammonium bromide system in the presence of additives, such as ureas, amino acids and sugars is reported. The change of standard Gibbs energy of solubilization (ΔG o ) for all of the additives was found to be negative. The values of change of standard enthalpy (ΔH o ) and that of standard entropy (TΔS o ) values were found to depend on the type and chemistry of the additive. The results were explained on the basis including chemistry of additives, their effect on water structure, and solubilization of additives either in the micellar or in aqueous phases.

Highly efficient base catalysis and sulfide oxidation reactions over new functionalized mesoporous polymers

Base catalyzed aldol condensation reactions and selective partial oxidation of sulfides are very important classes of reactions in synthetic organic chemistry. We have prepared a new alkali exchanged form of mesoporous polytriallylamine, OH-MPTA-1 and a Cr-grafted material Cr-MPTA-1 via the simple and facile in situ radical polymerization of a triallylamine template by organic–organic self-assembly of anionic surfactant systems. The materials have been characterized by elemental analysis, powder X-ray diffraction (XRD), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), UV-vis diffuse reflectance spectroscopy (DRS), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Powder XRD and TEM image analyses suggests the presence of mesophase and disordered wormhole-like mesopores in these samples. Our experimental results reveal that the alkali exchanged material OH-MPTA-1 acts as a very efficient base catalyst for the direct aldol reaction of different aromatic aldehydes with acetone. On the other hand, the Cr-grafted material Cr-MPTA-1, obtained through the reaction of potassium chromate with MPTA-1, acts as a very efficient catalyst for the liquid phase partial oxidation of sulfides to sulfoxides. Both OH-MPTA-1 and Cr-MPTA-1 can be recycled more than five times without an appreciable loss in activity for their respective catalytic reactions.

Hindered Diffusion of an Oil Drop Under Confinement and Surface Forces

Theoretical modeling of coalescence and drop–drop collision stability relies on an accurate physical understanding of surface forces, hydrodynamic drainage behavior, deformation, and internal drop flow. Brownian diffusion of alkane drops emulsified in aqueous solutions above a silica plate is measured using the total internal reflection microscope (TIRM). The behavior of drops over a range of separations is consistent with an immobile oil–water interface in both clean and anionic surfactant systems, counter to the hydrodynamic boundary conditions commonly assumed for fluid–fluid interfaces.

Anionic–cationic mixed surfactant systems: Micellar interaction of sodium dodecyl trioxyethylene sulfate with cationic gemini surfactants

The mixed surfactant systems of anionic sodium dodecyl trioxyethylene sulfate (SDES) and gemini surfactants (cationic) of the series N, N’- bis-(dimethyldodecyl)- α, ω-dialkanediammoniumdibromide, 12- s-12 ( s = 2, 4, 6) at different molar ratios were studied by surface tension measurements of aqueous solution as a function of total concentration under standard condition. Various parameters like critical micelle concentration (CMC), surface excess concentration ( Г max), minimum area per molecule ( A min), interaction parameter of mixed micelle and adsorption monolayer ( β m , β o) as well as thermodynamic and micellar properties have been determined using Clint, Rubingh, Maeda and Rosen approach. The strong interaction showing very low CMC and large negative interaction parameter β were due to weakening of the electrostatic head group repulsion which favors the mixed micelle formation. The results are discussed in terms of the structural characteristics and spacer chain of gemini surfactants and also in terms of the presence of EO group in SDES molecule. Gemini surfactants bind tightly with SDES by electrostatic, hydrophobic and ion–dipole interactions. Thermodynamic parameters for all three cationic–anionic mixed systems were evaluated. From excess free energy of micellization we can conclude that thermodynamically stable micelles are formed with strong synergistic interaction.

콘크리트용 기포제 종류 및 농도에 따른 기포의 특성

Bubbles within the foamed concrete manufactured by pre-foaming method is the main factor which affects the physical properties of foamed concrete such as density, strength, and porosity. Although many researches on foamed concrete have been continuously carried out, insufficient number of researches on the properties related to bubbles in the foamed concrete has been performed except for chemical application related researches. In order to make an optimal foamed concrete, study on the bubble properties must be pursued. In order to effectively implement bubbles in the manufacturing of foamed concrete, the bubble properties must be estimated. In this study, in order to determine the bubble properties, examination of the bubble properties according to types and foaming agent concentration was performed. An foaming agent used for this test were anionic surfactant, rosin, and protein system with the foaming agent concentration range of 0.05~13%. Test parameters considered in the study were foaming rate, foam volume, drainage solution volume, and bubble size. The study results showed that, regardless of foaming agent type, higher concentration of foaming agent showed an increase in the foaming rate. Also, the results showed that concentration of foaming agent affected bubble size, drainage solution volume change, and bubble distributions. With respect to the stability of the bubble, protein foaming agent was better than anion surfactant or rosin foaming agent. With respect to the bubble shape, anion surfactant and rosin formed bubbles had polygon shape where as protein formed bubbles had spherical shape.

Lipophilic Tail Architecture and Molecular Structure of Neutralizing Agent for the Controlled Rheology of Viscoelastic Fluid in Amino Acid-Based Anionic Surfactant System

The amino acid-based anionic surfactant, N-dodecanoylglutamic acid (designated as LAD), when neutralized with 2-aminoethanol (MEA), 2,2'-iminodiethanol (DEA), or 2,2',2''-nitrilotriethanol (TEA) forms globular type of micelles in aqueous system at 25 °C, and the viscosity of each solution is very close to that of pure water. Addition of cationic surfactants, e.g., tetradecyltrimethylammonium bromide (TTAB) or hexadecyltrimethylammonium bromide (CTAB), induced a sphere-to-rod transition, and the micelles grew axially, resulting in formation of viscoelastic wormlike micelles that could be described by a Maxwell model. The viscosity was ca. 5 orders of magnitude as large as that of water. The viscosity maximum was observed in zero-shear viscosity (η0) curves, and there was a phase separation to liquid crystal phase at higher cosurfactants concentration. The η0 curve shifted toward lower cosurfactant concentration, and the value of maximum viscosity (η0(max)) decreased by reducing lipophilic moiety of cosurfactant. Furthermore, the value of η0(max) decreased with decreasing the number of ethanol content per molecule of neutralizing agent. The η0 decays exponentially with the rise of temperature, following the Arrhenius type of behavior. However, addition of dodecyltrimethylammonium bromide (DTAB) increases viscosity only slightly; viscoelastic wormlike micelles are not formed.

Detection of DNA Sequence with Enhanced Sensitivity and Higher FRET Efficiency Using a Light-Emitting Polymer, Peptide Nucleic Acid Probe and Anionic Surfactant System

An improved strategy has been developed for detection of DNA sequence by using water-soluble cationic conjugated polymer (PFP)/single-strand (ss) DNA and peptide nucleic acid labeled with fluorescent dye (PNAC*), where an anionic surfactant (sodium dodecyl sulphate, SDS) system has been used to improve the sensitivity of the sensor. The method of detection is simple to use, fast and cost-effective. This method uses the phenomenon of Forester Resonance Energy Transfer (FRET). The detection sensitivity of the biosensor has been improved by about ten times by using the anionic surfactant. It is observed that the effect of surfactant is to increase the photoluminescence (PL) intensity of the PNAC* when the sequence of the DNA is complementary (to that of PNA probe). On the other hand when the two sequences are non-complementary, the PL intensity of the PNAC* is further reduced as compared to the case when surfactant was absent.

Enhanced stabilization of vesicles formed in mixed cationic and anionic surfactant systems by compressed gases

Herein we investigated the effects of six hydrocarbon gases (methane, ethane, propane, ethylene, propylene and isobutene) on mixed cationic–anionic surfactant solutions by phase behavior observation, turbidity, conductivity, and fluorescence spectra. It was found that all these gases could enhance the stability of vesicles formed in the mixed surfactant solutions. The pressure for the stable vesicle formation is decreased with the increasing gas molecular chain length. The possible mechanism for the enhanced vesicle stability by compressed gases was discussed.

Effects of surfactant micelles on solubilization and DPPH radical scavenging activity of Rutin

The interaction of the antioxidant Rutin with the radical DPPH (2,2-diphenyl-1-picrylhydrazyl) in presence of cationic (CTAB, TTAB, DTAB), non-ionic (Brij78, Brij58, Brij35), anionic (SDS) and mixed surfactant systems (CTAB-Brij58, DTAB-Brij35, SDS-Brij35) has been followed by spectrophotometric and tensiometric methods to evaluate the DPPH radical scavenging activity (RSA) of Rutin in these model self-assembled structures. The results show that the solubilization capacity of various single surfactant systems for both DPPH as well as Rutin followed the order cationics > non-ionics > anionic. The radical scavenging activity of Rutin in the solubilized form was higher within ionic micelles than in non-ionic micelles. However, the antioxidant exhibited enhanced activity for the radical in mixed cationic–non-ionic micelles compared with any of the single component micelles. In contrast, anionic–non-ionic mixed micelles modulated the activity of Rutin in-between that seen for pure anionic and non-ionic micelles only.

A surfactant type fluorescence probe for detecting micellar growth

We report on the detection of micellar growth in anionic, cationic, and catanionic surfactant systems using a novel surfactant type fluorescence probe, sodium 12-(N-dansyl)amino-dodecanate (12-DAN-ADA). The fluorescent group was incorporated in the tail of the surfactant which tethers the fluorescent group deep inside the apolar micellar cores. The fluorescence anisotropy of 12-DAN-ADA was found to be very sensitive for directly detecting the micellar growth in micelles containing oppositely charged surfactants, including cationic CTAB systems and mixed systems of oppositely charged surfactants (DEAB/SDS); in regard to the like charged SDS micellar systems, the sensitivity can be greatly enhanced by addition of a water soluble quencher which quenches the background fluorescence from the equilibrium population of free 12-DAN-ADA.

The photogalvanic conversion of solar energy into electrical energy in thiazine dye - anionic surfactant system

The photogalvanic conversion of solar energy into electrical energy in thiazine dye - anionic surfactant system

General rules for the scaling behavior of linear wormlike micelles formed in catanionic surfactant systems

We report in this work on the scaling behavior of wormlike micelles formed in a series of mixed systems of oppositely charged surfactants, including sodium decanote (SD)/hexadecyltrimethylammonium bromide (CTAB), sodium laurate (SL)/hexadecyltrimethylammonium bromide, sodium didecaminocystine (SDDC)/hexadecyltrimethylammonium bromide, and sodium dilauraminocystine (SDLC)/hexadecyltrimethylammonium bromide. Steady and dynamic rheological measurements were performed to characterize these wormlike micelles. The scaling behavior for these systems at various mixing ratios was systematically investigated and was compared with that given by the Cates model. It was found that the Cates law can be applied in these systems simply by manipulating the mixing ratio or the surfactant structure. Energetic analysis demonstrates that the scaling behavior of wormlike micelles in nonequimolar mixed cationic and anionic surfactant systems can be close to that predicted by the Cates model, if the electrostatic contribution is below a threshold value.

Salt effect on the rheological properties of the aqueous mixed cationic and anionic surfactant systems

The effect of NaBr on the aqueous two-phase regions of 0.10 mol kg −1 cetyltrimethylammonium bromide (CTAB)/sodium dodecyl sulfonate (AS)/H 2O mixed system at 318.15 K has been investigated. The aqueous two-phase region with excess AS or the aqueous two-phase region with excess CTAB all moves far from the equimolar line with the addition of NaBr. The effect of NaBr on the shear viscosities of the systems at the two isotropic single-phase regions has been also studied. At each isotropic single-phase region, one shear viscosity peak was observed for each m NaBr. The addition of NaBr to the mixed CTAB/AS/H 2O systems shifts the viscosity peaks away from the equimolar line, has stronger effect on the viscosity peak at the isotropic single-phase region with excess CTAB, and weaker effect on that with excess AS. Seven 0.10 mol kg −1 CTAB/AS/H 2O isotropic systems adjacent to the viscosity peaks were chosen to investigate the effect of NaBr on the shear viscosity. The rheological behaviors as well as the shear viscosity values of the seven chosen systems all change with the addition of NaBr. Salt-induced aqueous two-phase systems can be obtained with the addition of NaBr to the seven chosen systems. Just before the salt-induced aqueous two-phase separation was observed, the common tendency of the seven chosen systems is the decreases of the shear viscosities with the addition of NaBr, and those isotropic systems with NaBr aqueous solutions as solvents and very close to the phase boundaries are all thixotropic fluids. These results indicate that the salt-induced aqueous two-phase systems originate from thixotropic isotropic systems.

An NMR study of macromolecular aggregation in a model polymer-surfactant solution

A model complex-forming nonionic polymer-anionic surfactant system in aqueous solution has been studied at different surfactant concentrations. Using pulsed-field-gradient diffusion NMR spectroscopy, we obtain the self-diffusion coefficients of poly(ethylene glycol) (PEO) and sodium dodecyl sulfate (SDS) simultaneously and as a function of SDS concentration. In addition, we obtain NMR relaxation rates and chemical shifts as a function of SDS concentration. Within the context of a simple model, our experimental results yield the onset of aggregation of SDS on PEO chains (CAC=3.5 mM), a crossover concentration (C(2)=60 mM) which signals a sharp change in relaxation behavior, as well as an increase in free surfactant concentration and a critical concentration (C(m)=145 mM) which signals a distinct change in diffusion behavior and a crossover to a solution containing free micelles. C(m) also marks the concentration above which obstruction effects are definitely important. In addition, we obtain the concentration of SDS in monomeric form and in the form of free micelles, as well as the average number of SDS molecules in a PEO-SDS aggregate (N(Aggr)). Taken together, our results suggests continuous changes in the aggregation phenomenon over much of the concentration but with three distinct concentrations that signal changes in the nature of the aggregates.

Composition-Insensitive Highly Viscous Wormlike Micellar Solutions Formed in Anionic and Cationic Surfactant Systems

We investigated phase behavior and rheological properties of aqueous micellar phase formed in water/cocoyl glutamate neutralized with triethanol amine (CGT-n)/hexadecyl trimethylammonium salt (CTAB or CTAC) systems, where n is a degree of neutralization. Micellar phase appears in wide composition range with respect to the surfactant mixing fraction in ternary phase diagrams at 25 degrees C. At high mixing fraction of cationic surfactant in the water/CGT-n/CTAB systems, one can observe a highly viscous micellar phase in which worm-like micelles are expected to form. Contrary to conventional systems in which worm-like micelles are formed, the zero-shear viscosity of the micellar solution in the water/CGT-n/CTAB system with n=1.2 increases with the addition of cationic cosurfactant and once decreases after a maximum, then increases again and decreases after the second maximum. At n=1.5 and 2, highly viscous solution is observed in the relatively wide range of surfactant mixing fraction instead of two maxima of the viscosity curve observed at n=1.2. In the case of CTAC instead of CTAB we can observe narrow composition range for the maximum viscosity. Frequency sweep measurements were performed on the highly viscous samples in the water/CGT-1.5/CTAB system. Typical viscoelastic behavior of worm-like micellar solutions is observed; i.e. the curves of storage (G') and loss (G") moduli make a crossover and the data points of G' and G" can be fitted to the Maxwell model. Relaxation time against the mixing fraction of two surfactants behaves similarly to the zero-shear viscosity change, whereas the plateau modulus continuously increases in the plateau region for the zero-shear viscosity curve.

Transition from Vesicle Phase to Lamellar Phase in Salt-Free Catanionic Surfactant Solution

A salt-free cationic and anionic (catanionic) surfactant system was formed by mixing a double-tailed di-(2-ethylhexyl) phosphoric acid (DEHPA, commercial name P204), which is an excellent extractant of rare earth metal ions, with a single-tailed cationic trimethyltetradecylammonium hydroxide (TTAOH) in water. With the mole ratio (r) of DEHPA to TTAOH varying from 0.9 to 1, the phase transition occurred from a densely stacked vesicle phase (Lalphav) to a lamellar phase (Lalphal). Macroscopic properties, such as polarization and rheology, were measured and changed greatly during the course of the phase transition. When r was 0.96 or 0.98, the steady state shear curves exhibited two yield stress values, indicating the coexistence of the Lalphav phase and the Lalphal phase. The Lalphal phase formed in the salt-free and zero-charged system (r=1.0) is defective and undulating, which was confirmed by cryogenic transmission electron microscopy (cryo-TEM). The deuterium nuclear magnetic resonance spectra (2H NMR) showed that a single peak (singlet) split into two symmetric peaks (doublet) gradually, indicating the phase transition from the Lalphav phase to the Lalphal phase. Correspondingly, phosphorus nuclear magnetic resonance spectra (31P NMR) presented changes in both the chemical shift and the peak width, indicating that these two types of bilayer structures are of different anisotropy degrees and different viscosities. When the Lalphal phase is subjected to a certain shear force, it can be reversed to a Lalphav phase again, which was proved by rheological, 2H NMR, and 31P NMR measurements. Furthermore, a theoretical consideration about the formation of the defective and undulating Lalphal phase was taken into account from a viewpoint of energy.

Re-entrant Phase Behavior of a Concentrated Anionic Surfactant System with Strongly Binding Counterions

The phase behavior of the anionic surfactant sodium dodecyl sulfate (SDS) in the presence of the strongly binding counterion p-toluidine hydrochloride (PTHC) has been examined using small-angle X-ray diffraction and polarizing microscopy. A hexagonal-to-lamellar transition on varying the PTHC to SDS molar ratio (alpha) occurs through a nematic phase of rodlike micelles (Nc) --> isotropic (I) --> nematic of disklike micelles (N(D)) at a fixed surfactant concentration (phi). The lamellar phase is found to coexist with an isotropic phase (I') over a large region of the phase diagram. Deuterium nuclear magnetic resonance investigations of the phase behavior at phi = 0.4 confirm the transition from N(C) to N(D) on varying alpha. The viscoelastic and flow behaviors of the different phases were examined. A decrease in the steady shear viscosity across the different phases with increasing alpha suggests a decrease in the aspect ratio of the micellar aggregates. From the transient shear stress response of the N() and N(D) nematic phases in step shear experiments, they were characterized to be tumbling and flow aligning, respectively. Our studies reveal that by tuning the morphology of the surfactant micelles strongly binding counterions modify the phase behavior and rheological properties of concentrated surfactant solutions.

Effect of formation of calcium carbonate on foam stability in Neodol 25-3S anionic surfactant systems

The effect of oils and hardness on stability of foams made from solutions containing 0.01 wt% of three EO alcohol ethoxysulfate sodium salt of commercial anionic surfactant Neodol 25-3S was investigated. When dissolved calcium was present under alkaline conditions using Na 2CO 3 instead of NaOH as a pH regulator, solid CaCO 3 precipitated. It was found in the absence of oil that CaCO 3 particles did not destabilize foam, in contrast to those of the more hydrophobic calcium oleate. The rate of collapse of a foam column was also measured for foams generated from alkaline solutions of an anionic surfactant Neodol 25-3S containing dispersed drops of n-hexadecane, triolein, or mixtures of these oils with small amounts of oleic acid. Oils were added in increments up to oil to surfactant ratio of 1 on a weight basis and the hardness and pH of the aqueous solutions were fixed at 300 ppm and 9 respectively. It was found that triolein has almost no defoaming effect, but the defoaming effect of hexadecane was evident. The same trend was found with mixtures of n-hexadecane/triolein with addition of small amounts of oleic acid. The results of foam stability measurement in the presence of oil could be understood in terms of entry, spreading and bridging coefficients, i.e., ESB analysis. Moreover, as the initial concentration of carbonate ions increased, foam stability was greatly improved for both hexadecane/oleic acid and triolein/oleic acid oils. Evidently, CaCO 3 precipitated preferentially, reducing the number of calcium ions available to form calcium oleate.