Surfactant Ion Pair Research Articles

The Interaction Of Homodimer Styrylcyanine Dyes With Sodium Dodecyl Sulfate And Triton X-100.

Solubilization of the styrylcyanine dye Sbt ((E)-2-(4-(dimethylamino)styryl)-3-methylbenzo[d]thiazol-3-ium iodide) and its homodimers Dbt-5 and Dbt-10 in aqueous solution of sodium dodecyl sulfate and Triton X-100 has been studied by steady state and picosecond time-resolved fluorescence spectroscopy. At low concentration of sodium dodecyl sulfate in solution, between Sbt, Dbt-5 dyes molecules and surfactant ion pairs are formed followed by the formation non-luminescent H-aggregates. The nature of the interaction between molecules of dyes and surfactants has been revealed. The binding constants Ks of the dyes to the surfactants, free energy changes (ΔG0), the number of dye molecules (n) included in a single micelle and photophysical parameters have been determined. The degree of solubilization of dyes in micellar solution of Triton X-100 is higher as compared to sodium dodecyl sulfate and depends on the molecular weight and size of both dye molecules and micelles.

Dye-surfactant interaction in aqueous premicellar and micellar environments in the alkaline fading of di-positive methyl green carbocation

The alkaline fading of di-positive methyl green carbocation (MeG2+) has been studied in different aqueous premicellar and micellar environments of anionic, cationic as well as non-ionic surfactants. Mono- and di-negative anions like halides and sulphate have been found to show an inhibiting effect on the fading reaction owing to the formation of dye-anion ion-pair adduct before hydrolysis. The binding strength of the dye-anion ion-pair adduct is in the order: SO42- > I- > Br- > Cl- which rationalizes the same order of inhibition of the rate. A substantial change in the electronic spectra of MeG2+ in the presence of anionic surfactants, sodium dodecyl sulfate (SDS) and dioctyl sodium sulfosuccinate (AOT), in the pre-CMC region indicates a change in the equilibrium distribution of the two stereo isomers of the dye owing to the formation of MeG2+-surfactant ion-pair and ion-pair micelle. The premicellar rate inhibition of the fading reaction by SDS and AOT occurs due to the formation of 1:1 MeG2+-surfactant ion-pair (where ≥ 85 % of MeG2+ remain associated) through electrostatic interaction before hydrolysis. The cationic surfactant cetyltrimethylammonium bromide (CTAB) shows a retarding effect in the post-micellar region as the HO- ion experiences both electrostatic repulsion and steric hindrance to approach the carbocation centre of the dye, embedded in the micelle. The polar hydroxyl group and the polyoxyethylene groups present in the moiety of the non-ionic surfactant Brij35 assist to increase the local concentration of HO- and MeG2+ in the palisade layer resulting in a catalyzing effect on the fading reaction in the post CMC region. Both pre- and post-micellar rate effects have been analyzed quantitatively by different established kinetic models. Detailed calculations have been made to find out different enthalpy and entropy of activation as well as of binding in order to establish the nature of interactions between the dye MeG2+ and monomeric surfactant(s) /micelles as well as solvent molecules. Results of spectrophotometric and tensiometric investigations strongly support the existence of different molecular interactions in different stages of the hydrolysis reaction in the presence of surfactants.

Evidence of formation of dye–surfactant ion pair micelle in the anionic surfactant mediated alkaline fading of methyl violet carbocation

AbstractIn the submicellar solution of anionic surfactants sodium dodecyl sulfate (SDS) and dioctyl sodium sulfosuccinate (AOT), the alkaline fading of methyl violet (MV+) carbocation has been studied spectrophotometrically in the temperature range 293–308 K. The interaction behavior of the dye carbocation with the anionic surfactant and the observed submicellar rate retardation is consistent with the ion pair and subsequent ion‐pair micelle formation. The change in the spectral pattern along with a change in the peak intensity and shoulder intensity with increasing surfactant concentrations indicates the shifting of the equilibrium between the helical and distorted helical isomers of MV+ owing to the existence of dye–surfactant ion pair, ion‐pair micelles, and dye‐embedded micelles. This dynamic dye–surfactant ion‐ion interaction has been corroborated by the tensiometric studies. The decrease in the fading rate and the change in the spectral pattern in the presence of anion, especially I–, support the existence of the dye–anion interaction. The premicellar rate inhibition and the corresponding interaction have been accounted for by the use of two kinetic models namely, Olson–Simonson and Piszkiewicz cooperativity models. The cooperativity index value suggested a 1:1 dye–surfactant association in both the surfactants. The ratio of the concentration of the premicellar complex and the free dye cation indicates appreciable binding. The kinetic and thermodynamic parameters associated with the dye–surfactant complex have been explained in terms of dye–surfactant, dye–water, and surfactant–water interactions.

Microextraction–Colorimetric (Fluorimetric) Determination of Cationic and Anionic Surfactants in Food Products

A method is proposed for the determination of cationic and anionic surfactants in food products based on the use of dispersive liquid–liquid microextraction of surfactant ion pairs with organic reagents (eosin and acridine yellow) and measurements of the colorimetric parameters of the fluorescence of extracts using a smartphone. Upon the irradiation of the extracts of ion pairs anionic surfactant–acridine yellow and cationic surfactant–eosin with ultraviolet light (365 nm), green and yellow fluorescence were observed, respectively. The analytical signal (Ar) was the value of the colorimetric parameters in the RGB system: Ar = $$\sqrt {{{{{\text{(}}{{R}_{{\text{0}}}} - {{R}_{x}}{\text{)}}}}^{2}}{\text{ + (}}{{G}_{{\text{0}}}} - {{G}_{x}}{{{\text{)}}}^{2}}{\text{ + (}}{{B}_{{\text{0}}}} - {{B}_{x}}{{{\text{)}}}^{2}}} .$$ Procedures for determining the total amount of surfactants in food products (milk, vegetables and fruits, meat, and drinking water) are developed using an example of cetylpyridinium, myristalconium, benzalkonium, didecyldimethylammonium, alkyldimethyl(ethylbenzyl)ammonium, dodecyl sulfate and sodium alkylbenzenesulfonate chlorides. The limits of detection and quantification are in the ranges 0.005–0.05 and 0.01–0.1 mg/L, respectively. Calibration graphs are linear in the concentration range 0.01–1 mg/L with approximation confidence coefficients ≥0.99. The duration of analysis is 20–30 min; the relative standard deviation of the results of analysis does not exceed 0.24.

Catanionic Surfactant Self-Assembly in Protic Ionic Liquids.

Mixing of cationic and anionic surfactants in water can result in pseudo-double-tailed catanionic surfactant ion pairs that form lamellar phases or vesicles that are unstable toward electrolyte addition. Here we show that despite the very high ionic strengths, catanionic surfactants counterintuitively form a wider variety of self-assembled aggregates in pure ionic liquids (ILs, pure salts in a liquid phase) than in water, including micelles, vesicles, and lyotropic phases. Self-assembled structures only form when the IL is sufficiently polar to drive self-assembly through electrostatic interactions and/or H-bond networks, but the catanionic effect is manifested only when the IL does not itself exhibit pronounced amphiphilic nanostructure. This enables the type of catanionic aggregate formed to be designed by changing the hydrogen bonds between the ions through variation of the structures of the cation and anion. These results reveal an entirely new way of controlling catanionic surfactant self-assembly under nonaqueous and high-salt conditions.

Synthesis of ordered lamellar supermicroporous silica with rigid neutral and long-chain cationic composite templating route.

Using a mixture of neutral primary amine dehydroabietylamine (DHAA) and long-chain cetyltrimethyl ammonium bromide (CTAB) as the template, ordered lamellar supermicroporous silicas were synthesized with NaOH as the base source and tetraethylorthosilicate (TEOS) as the silica source. The concentrations of DHAA, CTAB, and NaOH in the synthesis system had great effects on the structural properties of the samples. When the molar ratio of components was nTEOS:nCTAB:nDHAA:nNaOH:nH2O = 1:0.114:0.00457:0.5:60, the material showed a lamellar phase with the highest ordering degree. By adding only a trace amount of DHAA into the synthesis system, the structure of the samples could be transformed from cubic phase to lamellar phase, since the added DHAA solubilized in CTAB micelles to change the effective surfactant ion pair packing parameter. The dosage of CTAB should be moderate; too high or too low will decay the ordering degree of the lamellar structure.A much higher concentration of NaOH resulted in an ethanol-rich solvent in which the DHAA did not solubilize in the micelles of CTAB, but adsorbed at the hydrophilic headgroup–solvent interface. Accordingly, a structural transformation from lamellar phase to hexagonal phase occurred.

Application of hollow-fiber liquid microextraction coupled with a surfactant ion pair solvent for the study of acrylamide and glycidamide in high temperature processed medicinal plant materials

A fresh hollow-fiber liquid microextraction coupled with surfactant ion pair solvent approach for the separation and extraction of acrylamide (AA) and glycidamide (GA) in high temperature processed medicinal plant materials (HTPMPMs) is described.

Kinetics, Thermodynamics, and Isothermic Evaluation in Sorption Study of Hazardous Dye Using Sodium Dodecylsulfate Physically Impregnated in Polyester‐Type Polyurethane Foam

AbstractUse of polyester‐type polyurethane foam (PUF) is an effective adsorbent for the removal of hazardous dye: crystal violet (CV) from an aqueous solution. In this adsorption study, the formation of hydrophobic ion pair (opposite charge attraction) between the charged species, i.e., cationic (basic) dye CV and anionic surfactant sodium dodecylsulfate (SDS) sorbed onto PUF. Chemical calculations were performed using quantum simulation to understand ion‐pair formation for CV–SDS at the semiempirical PM6 level. Adsorption studies were performed using 200 mg cylindrical PUF with an overhead stirrer in solutions containing varying compositions of the dye–surfactant mixture. The equilibrium thermodynamics and kinetics of the adsorption process were studies by measuring CV dye removal as a function of time and temperature. Results show that the formation of the dye–surfactant ion pair is necessary for effective adsorption onto PUF. Various adsorption isotherms, viz., Langmuir, Freundlich, Temkin, Dubinin–Radushkevich (DRK), Harkin‐Jura, and several kinetic models, viz., pseudo‐first order, pseudo‐second order, Elovich, and Intraparticle diffusion were used to fit the spectrophotometric result. The equilibrium adsorption data fit to the Langmuir isotherm gives the maximum adsorption of PUF as 33.39 mg g−1 from 200 mL 5.0 × 10−5 mol L−1 CV solution at 298.15 K. The kinetics study showed that the overall adsorption process follows pseudo‐second‐order kinetics. The Morris–Weber model suggests that an intraparticle diffusion process is active in controlling the adsorption rate. The Freundlich, Temkin, DRK adsorption isotherms showed that solute dye transfers from solution to the PUF adsorbent surface through physical adsorption. The Langmuir and Harkin‐Jura adsorption isotherms suggest that the adsorbent surface is homogeneous in nature. The thermodynamic data showed that the adsorption process is spontaneous and endothermic with a positive enthalpy change and a negative change in Gibb's energy.

Effect of the nature of counterion on the micellar properties of cationic surfactants: a conductometric study

ABSTRACTInteraction of cationic surfactants, tetradecyltrimethylammium bromide (TTAB) and tetradecyltrimethylammonium chloride (TTAC) with anionic dye, tartrazine in aqueous solution has been investigated employing conductometric technique. The free energy of transfer of hydrophobic chain, , surface contribution, and their transfer values, and , free energy, , enthalpy, , and entropy, of micellisation have been calculated. A marked decrease in the critical micelle concentration for TTAB compared to TTAC indicates dramatic role of the smaller counterion Br− over the bigger counterion Cl−. Formation of dye–surfactant ion-pairs which behave as nonionic surfactant has been proposed. Higher negative and positive values for TTAB than TTAC are attributed to difference in the size and nature of the counterions Br− and Cl−. Negative and values clearly suggest that micellisation of TTAB and TTAC is thermodynamically spontaneous and exothermic in nature. As ), it suggests that the process of micellisation is entropy dominated for the two surfactants.

Thermodynamic Investigation of Anionic Dye-Cationic Surfactant Ion Pair Formation in Water-Acetonitrile Mixed Solvent

Thermodynamic Investigation of Anionic Dye-Cationic Surfactant Ion Pair Formation in Water-Acetonitrile Mixed Solvent

Molecular interaction of Congo Red with conventional and cationic gemini surfactants

Interaction of tetradecyltrimethylammonium bromide (TTAB), octylophenylpolyoxyethylene ether (TX-100), sodium dodecylsulfate (SDS), N,N′-ditetradecyl-N,N,N′,N′-tetramethyl-N,N′-butanediyl-diammonium dibromide (14,4,14) and N,N′-didodecyl-N,N,N′,N′-tetramethyl-N,N′-butanediyl-diammonium dibromide (12,4,12) with an anionic diazo dye, Congo Red, was investigated using conductometry, spectroscopy, tensiometry, and pulsed field gradient NMR (PFG-NMR). The formation of dye–surfactant ion pairs, their small mixed aggregates (below the critical micelle concentration (CMC) of these surfactants) and surfactant micelles were detected successfully. Above the CMC, the dye reverted to its monomeric state and solubilized in the micelles. Job's method was used to determine the stoichiometric ratio of dye and surfactant in ion pairs and revealed the formation of more hydrophile ion pairs for geminis compared to their conventional analogs. Quantitative results obtained from tensiometry indicated the existence of considerable synergism for cationic surfactants and antagonism for anionic SDS. In addition, the synergism observed for TX-100 revealed the effect of π–π stacking and hydrophobic forces on ion pair and mixed micelle formation. The increase of dye–surfactant interactions by increasing the electrical charge and chain length of cationic surfactants confirmed the importance of both electrostatic and hydrophobic forces in binary dye/surfactant systems. The hydrodynamic radii of the micelles were determined by self-diffusion coefficient measurements. The average size of the cationic and nonionic micelles increased in the presence of CR molecules.

Intermolecular interactions between a dye and cationic surfactants: Effects of alkyl chain, head group, and counterion

The interactions between an anionic dye and cationic surfactants were investigated using surface tension measurements, spectroscopy, conductometry, and pulsed field gradient NMR (PFG-NMR). Spectroscopic and surface property characterization of the solution as a function of surfactant concentration in the presence of the dye revealed formation of three species: a dye–surfactant ion pair, small mixed aggregates of the dye and surfactant (below the critical micelle concentration (CMC) of these surfactants), and micelles composed of the cationic surfactant. Above the CMC, the dye reverted to its monomeric state or bound to the surface of the micelle. Chemometric resolution analysis confirmed the formation of three species. The hydrodynamic radii of the micelles were determined by self-diffusion coefficient measurements. The average size of the micelles was larger in the presence than in the absence of the dye. Regular solution theory was used to describe the synergistically enhanced ability to form mixed aggregates of dyes and surfactants.

Novel cationic surfactant ion pair based solid phase microextraction fiber for nano-level analysis of BTEX

Ion pair of cationic surfactant (cetytrimethylammonium bromide) and tungestosilicic acid incorporated in PVC matrix, was used for coating a piece of copper wire as a new high sensitive SPME fiber in extraction and determination of BTEX compounds from the headspace of water samples prior to GC/FID analysis. Under optimum extraction conditions, limits of detection for benzene, toluene, ethylbenzene, p-xylene, m-xylene and o-xylene were found to be 1.18, 5.61, 0.87, 0.29, 0.22 and 0.33ngL−1 respectively. Low detection limits, wide linear dynamic ranges, good reproducibility (RSD% 1.48–4.27), high fiber capacity and high mechanical durability are some of the most important advantages of the new fiber.

Novel Perchlorate Selective Electrode Based on Neutral Surfactant Ion-Pair Complex of Dodecyltrimethylammonium-Perchlorate

Novel perchlorate selective polymeric membrane electrode based on recently synthesized neutral ion-pair complex dodecyltrimethylammonium-perchlorate () has been reported to be exhibiting Nernstian slope (−57.34 mV/dec) for perchlorate ions over a wide concentration range (1.00 × 10−1 M–5.00 × 10−6 M) with lower detection limit of 2.51 × 10−6 M. Proposed electrode has fast response time (10 s) and wide pH range (1.40–6.05). Selectivity coefficient values indicate its ability to preferentially sense perchlorate ions in presence of various secondary anions. Application of the proposed electrode has been studied by potentiometric estimation of perchlorate ions in synthetic water samples.

Synthesis and properties of cationic surfactants with tuned hydrophylicity

A series of pyridinium-based cationic surfactants has been synthesised and their amphiphilic properties have been studied by conductivity and surface tension measurements. The modification of the substitution pattern on the pyridinium ring by hydrophobic moieties (methyl vs. hydrogen and presence or not of condensed benzene ring) gave the opportunity to investigate structure–activity relationships. Characterization by conductivity and surface tension measurements shed light on the behaviour at the air/water interface and in the micellar environment. In particular, the tendency to form ion pairs at very low concentration was evidenced for all the surfactants substituted on the ring, but not for the simple pyridinium ones. The formation of ion pairs affects both the conductivity and the surface tension plots, showing that a series of steps is involved during the adsorption to the air/water surface. An attempt was made to qualify the single steps in the adsorption at the surface layer. Those steps were attributed to different chemical species (free surfactant ions or ion pairs) and to different arrangements of the surfactant. This work also represents a contribution of investigation at very low surfactant concentrations and high surface tension values.

Premicellar and micelle formation behavior of aqueous anionic surfactants in the presence of triphenylmethane dyes: protonation of dye in ion pair micelles

AbstractThe premicellar and micelle formation behaviors of four cationic triphenylmethane dyes, viz, Pararosaniline (RN), Crystal violet (CV), Ethyl violet (EV), and Malachite green (MG), in aqueous anionic surfactant solutions of sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS), and sodium dodecyl sulfonate (SDSN) have been studied by spectral and surface tension measurements. The study was carried out within a pH range where the dyes are stable in their quinoid forms. The dyes have been found to form dye–surfactant ion pairs (DSIPs) with the surfactants, at the surfactant concentrations well below their critical micelle concentration, CMC*. The DSIPs behave like nonionic surfactants and form an air–water interfacial monolayer. The DSIPs have a lower critical micelle concentration (CMCIP), greater efficiency, and lower effectiveness than the corresponding pure surfactants. As the surfactant concentration is increased below the CMC*, the DSIPs start forming micelles of their own where the dye gets protonated and exists as a protonated dye–surfactant ion pair (PDSIP) in the ion pair micelles. As the concentration of the surfactant exceeds the CMC* of the pure surfactant, the protonation reverses gradually with the dye remaining in the micelles in solubilized form and the DSIPs in the air–water interfacial monolayer are replaced by pure surfactants. The distorted helical isomeric form (isomer B) of the dyes is favored in the PDSIPs. Copyright © 2009 John Wiley & Sons, Ltd.

Influence of ethanol addition on the modification of montmorillonite by hexadecyl trimethylammonium bromide

Although modification of montmorillonite (MMT) with cationic surfactants has been studied extensively, the influence of the reaction medium has not been investigated systematically. The present paper reports the influence of ethanol on the modification of MMT using hexadecyl trimethylammonium bromide (HDTMA-Br). Wide angle X-ray diffraction (WAXD) and thermogravimetric analysis (TGA) were used to characterize the organically modified montmorillonite (OMMT). The addition of ethanol had little influence on the cation exchange, but affected greatly on the intercalation of the surfactant ion pairs into the interlayer space when HDTMA exceed the cation exchange capacity (CEC) of MMT. The increase of the ethanol/water ratio increased the critical micelle concentration (CMC) of HDTMA-Br solution. The intercalation of HDTMA ion pairs proceeded when the HDTMA concentration was above the CMC. It was confirmed that both of basal spacing and organic fraction followed sigmoid functions for OMMT prepared with excess HDTMA-Br amount and various surfactant concentrations under different CMC.

Premicellar and micelle formation behavior of dye surfactant ion pairs in aqueous solutions: Deprotonation of dye in ion pair micelles

The premicellar and micelle formation behavior of dye surfactant ion pairs in aqueous solutions monitored by surface tension and spectroscopic measurements has been described. The measurements have been made for three anionic sulfonephthalein dyes and cationic surfactants of different chain lengths, head groups, and counterions. The observations have been attributed to the formation of closely packed dye surfactant ion pairs which is similar to nonionic surfactants in very dilute concentrations of the surfactant. These ion pairs dominate in the monolayer at the air–water interface of the aqueous dye surfactant solutions below the CMC of the pure surfactant. It has been shown that the dye in the ion pair deprotonates on micelle formation by the ion pair surfactants at near CMC but submicellar surfactant concentrations. The results of an equilibrium study at varying pH agree with the model of deprotonated 1:1 dye–surfactant ion pair formation in the near CMC submicellar solutions. At concentrations above the CMC of the cationic surfactant the dye is solubilized in normal micelles and the monolayer at the air–water interface consists of the cationic surfactant alone even in the presence of the dyes.

Conductometric studies of interaction between anionic dyes and cetylpyridinium bromide in water–alcohol mixed solvents

The interactions between two anionic dyes and a cationic surfactant were studied by conductometric technique. The conductance of aqueous solutions of methyl orange (MO) and methyl red (MR) was measured in the presence of a cationic surfactant, cetylpyridinium bromide (CPB) at different temperatures in water–ethanol, water–propanol and water–butanol mixed solvents, containing different concentration of alcohols. The equilibrium constants and other thermodynamic functions for the process of dye–surfactant ion pair formation were calculated on the basis of a theoretical model. The results showed that the presence of alcohol, as well as increasing the length of the alcohol chain, decreases the tendency for ion pair formation. The results have shown that an increase in temperature lowers the tendency for ion pair formation as the equilibrium constants decrease with increasing temperature. According to the results, long range as well as short range interactions are responsible for the formation of the ion pair. The importance of long range electrical forces is basically to bring the dye anion and the surfactant cation close enough to enable the action of short range interactions whose contribution represents the major part of the standard free energy change for the formation of the anionic dye–cationic surfactant ion pair. By using the association constant ( K 1) for the first step of the association [ D − + S + → ( DS)°], the standard free energy change, standard enthalpy change, and standard entropy change of the association were calculated at low surfactant concentrations.

Studies of Langmuir−Blodgett Films of an Ion Pair Metal Complex Containing Eu(III)-Ru(II) Dual Chromophores

A surfactant ion-pair complex, [Ru(bpy)(2)L][Eu(NTA)(4)](2) (in which L = 1-docosyl-2-(2- pyridyl)benzimidazole, bpy = 2,2'-bipyridine, and NTA = 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedionato) has been synthesized. The surface pressure-area isotherm measurements show that the complex forms a stable Langmuir film at the air-water interface without adding any electrolytes into the subphase. The monolayers formed at the surface pressures of 5 mN m(-1) and 20 mN m(-1), have been successfully transferred onto glass and quartz substrates with the transfer ratios close to unity. The Langmuir-Blodgett films were studied by UV-visible, infrared, and emission spectroscopies, atomic force microscopy, and cyclic voltammetry. The optical, redox, and morphology properties of the LB films were found to be significantly affected by the target surface pressures used for the film depositions.