Surfactants In Mixed Micelles Research Articles

Study on Mixed Micelles of Cationic Gemini Surfactants Having Hydroxyl Groups in the Spacers with Conventional Cationic Surfactants: Effects of Spacer Group and Hydrocarbon Tail Length

Gemini surfactants, being more surface-active than their conventional counterparts, have potential applications in various industries. The properties of mixed surfactant systems are far better than those of neat surfactants in many cases, and as a result, mixed surfactants are used in many industrial applications. In the present work, the micellar properties of binary mixtures of the monomeric cationic surfactants hexadecyltrimethylammonium bromide (CTAB), tetradecyltrimethylammonium bromide (TTAB), and dodecyltrimethylammonium bromide (DTAB) with the cationic gemini surfactants 1,3-bis(dodecyl-N,N-dimethylammonium bromide)-2-propanol and 1,4-bis(dodecyl-N,N-dimethylammonium bromide)-2,3-butanediol were studied in aqueous solution at 303.15 K by means of conductivity, steady-state fluorescence, and fluorescence anisotropy techniques. The presence of a small amount of gemini surfactant was found to improve the physicochemical properties of the conventional surfactant. For example, the cmc value of DTAB was reduced to one-sixth of its original value in the presence of 0.1 mole fraction of a gemini surfactant. The spacer group of the gemini surfactant and the hydrocarbon chain of the monomeric surfactant play a significant role in the interactions between the surfactants in mixed micelles. These interactions are greatest when there are similarities in the structures of their hydrocarbon chains; however, the micellization process is favored by increasing hydrophobicity of the monomeric surfactant. The microenvironments of mixed micelles were studied using fluorescence techniques.

Analysis of Mixed Micellar Behavior of Promazine Hydrochloride with Surfactants in Aqueous Medium at Different Temperatures and Compositions

Abstract Mixed micellization behavior of an amphiphilic phenothiazine drug promazine hydrochloride (PMZ) in the presence of conventional dodecyltrimethylammonium bromide (DTAB) as well as gemini 1,4-bis(N-dodecyl-N,N-dimethylammonium)butane bromide (12-4-12) cationic surfactants has been studied at four different fixed temperatures and compositions by conductometric technique. The experimental data have been analysed by considering different theoretical models of Clint, Rubingh, Motomura and Rodenas. The cmc and cmcid values indicate mixed micelle formation between the components and strong synergism is observed in the mixed systems. The micellar (actual) mole fractions of surfactants (χ 1 Rub, χ 1 M, χ 1 Rod and χ 1 id), calculated on the basis of different theoretical proposed models used in the present study, show greater contribution of surfactants in mixed micelles. Activity coefficients (f 1 and f 2) are always less than unity indicating nonideality in the systems. Thermodynamic parameters are also evaluated and discussed which suggest that at higher temperatures dehydration of hydrophobic part of the drug takes place.

Interaction between Zwitterionic Surfactants and Amphiphilic Drug: A Tensiometric Study

Abstract The physicochemical properties, viz, critical micelle concentration (cmc), surface excess concentration (Γ max), minimum area per head group (A min) of zwitterionic surfactants (designated as n(−)-2-m(+); n = 8, 10, 12 and m = 12, 14, 16) and their mixtures with amphiphilic antidepressant drug amitriptyline hydrochloride (AMT) were determined by using surface tension measurements. The cmc and ideal cmc (cmcid) values along with interaction parameters, β m and β σ (calculated using Rubingh's and Rosen's models), suggest attractive interactions among the components. The Krafft temperature measurements also indicate strong attractive interactions. Γ max (or A min) increases (or decreases) with the addition of gemini surfactant; the values being closer to that of the drug. These values and micellar mole fraction (X1 m-calculated from Rubingh's model and X 1 Moto-calculated from Motomura's model) indicate larger contribution of gemini surfactants in mixed micelles and smaller contribution at air/solution interface (as mole fraction values at interface, X 1 σ , are slightly smaller than X 1 m). The standard Gibbs energy of micellization (Δ G micº) and adsorption (Δ G adº) as well as excess energy of mixing (Δ G ex m) are all negative. All these results suggest higher stability of the mixed systems. UV absorbance results also suggest that the mixed micelles are stable for several days.

Mixed micellization between amphiphilic drug promethazine hydrochloride and cationic surfactant (conventional as well as gemini)

The micellization behavior of an amphiphilic drug (promethazine hydrochloride (PMT)) in the presence of cationic surfactants (conventional as well as gemini) has been investigated conductometrically at different concentrations and temperatures. The micellar mole fractions of the surfactant (X1Rub, X1M, X1Rod, and X1id), calculated by different proposed models, show greater contribution of surfactant in mixed micelle and increases with the increase in concentration of the surfactant. Although α1 (mole fraction of surfactant) is higher for DTAB than that of 12-4-12, the contribution of 12-4-12 is almost equal to that of DTAB. The interaction parameter (β) is negative at all temperatures and at all compositions indicating attractive interactions. Activity coefficients (f1 and f2) are always less than unity suggesting nonideality in the systems. Thermodynamic parameters suggest dehydration of the hydrophobic part of the drug at or above a certain temperature.

Liposome Solubilization Induced by Surfactant Molecules in a Microchip

The dynamics of liposome solubilization was monitored by dynamic light scattering and optical microscopy. A newly designed Y-shape microchannel connected to a room was incorporated into a microchip and the reaction processes of the liposome suspension and surfactant solution were observed in the room after mixing the two fluids and stopping the flow. By using this microchip, we succeeded in real-time monitoring of liposome solubilization and the following dynamic processes of solubilization were proposed: 1) Deformed liposomes become spherical. 2) The liposome size increases until the surfactant/liposome ratio in the liposome membrane reaches a threshold value. 3) Mixed micelles of surfactants and phospholipids are released and the liposomes collapse.

Micellization and interfacial behavior of binary surfactant mixtures based on cationic geminis and nonionic Tweens

The behavior of mixed cationic gemini–nonionic surfactant systems in solution and at interface have been studied by surface tension measurements. Cationic geminis used were alkanediyl- α, ω-bis(dimethylhexadecylammonium bromide) and nonionic surfactants were the Tweens (Tween 20, 40, 60 and 80). The critical micelle concentration ( cmc) values of the mixtures are lower than the values of individual surfactants and decrease with the increase in stoichiometric mole fraction of Tweens in the solution. This shows nonideal, synergistic mixing of the two components. Other parameters calculated were cmc at ideal mixing conditions ( cmc id), surface excess concentration ( Γ exc) and minimum area per surfactant head group ( A min). The Gibbs energy of micellization ( Δ G m o ), Gibbs energy of adsorption ( Δ G ad o ), mole fraction of surfactants in mixed micelles ( X 1 m ) and monolayers ( X 1 σ ) , and interaction parameters ( β m , β σ ) were also evaluated. These values also indicate synergism in the system and greater contribution of the nonionic component in the mixtures.

Association of anionic surfactant mixed micelles with hydrophobically modified ethyl(hydroxyethyl)cellulose

Some aspects of ethyl(hydroxyethyl)cellulose (EHEC) aqueous behavior in the presence of ionic surfactants are described in the literature; however, most of the studies reported deal with moderately concentrated solutions. Few studies have been carried out in the dilute regime using mixtures of anionic surfactants sodium dodecyl sulfate (SDS) and sodium dodecanoate (SDoD). The main proposal of this work is to investigate the interaction of EHEC in diluted regime and to verify the mixtures of the surfactants SDS and SDoD. Mixtures of EHEC and SDoD were investigated using surface tension, conductivity and transmittance measurements. Parallel experiments with EHEC in mixtures with SDS were carried out. The formation of micelles of SDoD mixed with SDS in the absence and presence of EHEC was also investigated. The transmittance vs. [SDS] and [SDoD] profiles exhibit bands that, in conjunction with conductivity and surface tension data, aid a better understanding of the behaviors of EHEC–SDS–SDoD–water solutions.

Small angle neutron scattering study on the effect of molecular interaction on the structural properties of cationic and nonionic surfactant mixed micelles in aqueous solutions

We studied aqueous micellar solutions of mixtures of the nonionic surfactant octaethylene glycol mono-n-tetradecyl ether, C 14E 8, and the cationic surfactant tetradecyl trimethylammoniumbromide, TTAB, through small angle neutron scattering. The mixed micelles maintained their spherical shape without effects of the charged molecules over the whole mixing range, from pure nonionic surfactant to pure cationic surfactant micelles. At very low composition ( α = 0.04) of the charged TTAB molecules, the nonionic–cationic mixed micelles have a maximum aggregation number of the micelles. This aggregation phenomenon is described well by molecular–thermodynamic theory. There was synergistic interaction between the surfactants, leading to a maximum aggregation number of the micelles. This study presents an example of a spherical micelle for the synergistic interaction in nonionic–ionic surfactant mixtures.

Partitioning and Localization of Fragrances in Surfactant Mixed Micelles

AbstractThe localization and dynamics of fragrance compounds in surfactant micelles are studied systematically in dependence on the hydrophobicity and chemical structure of the molecules. A broad range of fragrance molecules varying in octanol/water partition coefficientsPowis employed as probe molecules in an aqueous micellar solution, containing anionic and nonionic surfactants. Diffusion coefficients of surfactants and fragrances obtained by Pulsed Field Gradient (PFG)‐NMR yield the micelle/water distribution equilibrium. Three distinct regions along the log(Pow) axis are identified: hydrophilic fragrances (log(Pow) < 2) distribute almost equally between micellar and aqueous phases whereas hydrophobic fragrances (log(Pow) > 3.5) are fully solubilized in the micelles. A steep increase of the incorporated fraction occurs in the intermediate log(Pow) region. Here, distinct micelle swelling is found, while the incorporation of very hydrophobic fragrances does not lead to swelling. The chemical structure of the probe molecules, in addition to hydrophobicity, influences fragrance partitioning and micelle swelling. Structural criteria causing a decrease of the aggregate curvature (flattening) are identified.2H‐NMR spin relaxation experiments of selectively deuterated fragrances are performed monitoring local mobility of fragrance and leading to conclusions about their incorporation into either micellar interface or micelle core. The tendencies of different fragrance molecules (i) to cause interfacial incorporation, (ii) to lead to a flattening of the micellar curvature and (iii) to incorporate into micelles are shown to be correlated.

Interfacial and micellar properties of anionic azo dye-surfactant binary systems

The association of an anionic dye C.I. Reactive Orange 16 (RO16) and different types of surfactants, i.e., anionic surfactant sodium dodecylsulfate, nonionic surfactants poly(oxyethylene) ethers (C m POE10, m = 12, 16, and 18; C12POE n , n = 4, 10, and 23), was investigated using tensiometry in a certain micellar concentration range. RO16 was shown to aggregate in water when its concentration is above the threshold value. The surface tension lowering and critical micellar concentration (CMC) values were interpreted on the same grounds as those for surfactants mixtures. The tensiometric measurements of dye-surfactant systems are carried out as a function of the molar concentration of solution at 25°C. Using Rubingh’s regular solution theory, the values of interaction parameters were found to be negative for all studied binary mixtures. These negative values indicate that there is an attractive interaction of the surfactants in mixed micelles and reflect synergistic behavior of a mixture. In all studied systems, deviations from ideal behavior were observed depending on the type of surfactant. Interaction parameters calculated using regular solution theory are changed from −2.62 to −12.43. The smallest deviation from ideal behavior is obtained for the RO16-C12POE4 mixed system; i.e., in the case when nonionic surfactant has the shortest alkyl chain and the smallest number of ethylene oxide units.

Self-Assembly in Mixed Dialkyl Chain Cationic−Nonionic Surfactant Mixtures: Dihexadecyldimethyl Ammonium Bromide−Monododecyl Hexaethylene Glycol (Monododecyl Dodecaethylene Glycol) Mixtures

The self-assembly of dialkyl chain cationic surfactant dihexadecyldimethyl ammonium bromide, DHDAB, and nonionic surfactants monododecyl hexaethylene glycol, C(12)E(6), and monododecyl dodecaethylene glycol, C(12)E(12), mixtures has been studied using predominantly small-angle neutron scattering, SANS. The scattering data have been used to produce a detailed phase diagram for the two surfactant mixtures and to quantify the microstructure in the different regions of the phase diagram. For cationic-surfactant-rich compositions, the microstructure is in the form of bilamellar, blv, or multilamellar, mlv, vesicles at low surfactant concentrations and is in an L(beta) lamellar phase at higher surfactant concentrations. For nonionic-rich compositions, the microstructure is predominantly in the form of relatively small globular mixed surfactant micelles, L(1). At intermediate compositions, there is an extensive mixed (blv/mlv) L(beta)/L(1) region. Although broadly similar, in detail there are significant differences in the phase behavior of DHDAB/C(12)E(6) and DHDAB/C(12)E(12) as a result of the increasing curvature associated with C(12)E(12) aggregates compared to that of C 12E 6 aggregates. For the DHDAB/C(12)E(12) mixture, the mixed (blv/mlv) L(beta)/L(1) phase region is more extensive. Furthermore, C(12)E(12) has a greater impact upon the rigidity of the bilayer in the blv, mlv, and L(beta) regions than is the case for C(12)E(6). The general features of the phase behavior are also reminiscent of that observed in phospholipid/surfactant mixtures and other related systems.

Small angle neutron scattering measurements of aggregation behaviour of mixed micelles of conventional surfactants with triblock polymer L64

Small angle neutron scattering (SANS) technique has been used to study the aggregation behaviour of binary mixtures of cationic surfactants such as hexadecyltrimethylammoniumbromide (HTAB), tetradecyltrimethylammonium bromide (TTAB) and dodecyltrimethylammonium bromide (DTAB) and nonionic surfactant (Triton X-100) with triblock polymer L64. The interactions between surfactants and triblock polymers have been explained on the basis of parameters like aggregation number, charge fraction and axial ratio. The SANS analysis indicated that the shape of micelles of cationic surfactants (HTAB, TTAB and DTAB), mixed micelles of these surfactants with triblock polymer (L64) and pure Triton X-100 is prolate ellipsoidal. For pure cationic surfactants DTAB to HTAB, there is an increase in aggregation number and decrease in charge fraction, which indicates that, the micelle grow in size with increase in the number of carbon atoms in hydrophobic tail. In case of mixture of cationic surfactant with triblock polymer (L64), the mixed micelles appear to grow in size with increase in the concentration of triblock polymer. But the shape of mixed micelle is determined largely by cationic surfactant even at very high concentration of triblock polymer and the shape of mixed micelle is prolate ellipsoidal. On the other hand, the mixed micellization of nonionic surfactant (Triton X-100) with triblock polymer (L64) are completely dominated by concentration of triblock polymer. The micellar size decreases with the increase in the concentration of triblock polymer L64. The shape of mixed micelle is spherical, same as in case of pure triblock polymer.

Conductometric study of antidepressant drug–cationic surfactant mixed micelles in aqueous solution

Conductivity measurements have been carried out on aqueous solutions of two antidepressant drugs (nortriptyline hydrochloride and clomipramine hydrochloride) with four cationic surfactants (monomeric: cetyltrimethylammonium bromide, tetradecylammonium bromide; dimeric: 1,5-pentanediyl-α-ω-bis(hexadecyldimethylammonium bromide), 1,4-butanediyl-α,ω-bis(hexadecyldimethylammonium bromide) as well as with sodium chloride. Counterions from NaCl adsorb to the charged headgroup of the drug molecules and reduce the repulsion, hence cmc decreases. cmc values decreased with the addition of surfactants indicating mixed micelle formation. Experimental mole fraction of surfactants in micelle ( X 1) and their ideal values ( X 1 id ) also support this explanation. Interaction parameter, β, and excess free energy of micellization are negative suggesting synergism in mixed state. Activity coefficients are less than unity which means non-ideal mixing.

Synergistic Behavior of a Triblock Copolymer with Anionic and Cationic Surfactants in Aqueous Solution

AbstractThe synergistic behavior of poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO–PPO–PEO) triblock copolymer in aqueous solution with the synthesized anionic surfactants [decyl sulfonate (A10), myristyl sulfonate (A14) and cetyl sulfonate (A16)] and cationic surfactants [decyl pyridinium bromide (C10), myristyl peridinium bromide (C14) and cetyl pyridinium bromide (C16)] was investigated using a surface tension technique at 25 °C. The results show that the CMC values of binary mixtures for anionic and cationic surfactants with the triblock copolymer are lower than that of single surfactants. The synergistic interaction between surfactant molecules and copolymer molecules in binary mixed solution enhance the adsorption of surfactant molecules at the interface. The micellar mole fractions (Xm) and the interaction parameter (β) of these surfactants in mixed micelles were determined.

Enhanced soil flushing of phenanthrene by anionic–nonionic mixed surfactant

Laboratory column experiments were conducted to investigate the performance of anionic–nonionic mixed surfactant, sodium dodecyl sulfate (SDS) with Triton X-100 (TX100), in enhancing phenanthrene flushing for contaminated soil in an aim to improve the efficiency of surfactant remediation technology. The experimental results showed that the sorption of TX100 onto soil was severely restricted in the presence of SDS in batch and column experiments and decreased with the increasing mass fraction of SDS in mixed surfactant solutions; meanwhile the enhanced solubilization of phenanthrene by SDS–TX100 mixed surfactant was greater than that by individual surfactant. These results can be attributed to the formation of mixed surfactant micelles in solution. The column flushing experiments showed that the flushing efficiencies for phenanthrene-contaminated soil by SDS–TX100 mixed surfactants were greater than that by individual surfactant and increased with the increasing mass fraction of SDS in mixed surfactant solutions.

Charged molecular effect on the degree of ordering of mesostructured silica thin film templated by mixed ionic micelles

We have synthesized highly oriented mesostructured silica thin films templated with nonionic and cationic mixed surfactant micelles by a solvent evaporation-induced self-assembly process. The mesostructured silica thin films showed constant body-centered cubic lattice structures over a wide range of mixing mole ratios of the cationic surfactant in the nonionic surfactant-rich phase. The degree of ordering of the mixed micellar arrays in the mesostructured silica thin films was enhanced by tuning the mixing mole ratio of the cationic surfactants to nonionic surfactant.

Synthesis and phase behaviors of bicontinuous cubic mesoporous silica from triblock copolymer mixed anionic surfactant

Highly ordered mesoporous silicas with bicontinuous cubic structure (space group of Ia 3 ¯ d ) have been synthesized via a sol–gel route by the condensation of tetraethyl orthosilicate (TEOS) in a mixed surfactant system, poly(ethylene oxide)- b-poly(propylene oxide)- b-poly(ethylene oxide) triblock copolymer P123 (EO 20PO 70EO 20) mixed with sodium dodecylbenzene sulfonate (SDBS). Small-angle powder XRD, TEM, dynamic light scattering (DLS), and nitrogen adsorption were utilized to determine the phase diagram and illustrate the factors that define the phase boundary lines. The results show that the bicontinuous cubic Ia 3 ¯ d mesophase can be reproducibly obtained in a large phase area in the acid concentration–temperature phase diagram, which is induced by anionic surfactant SDBS. A mesophase transformation from 2-D hexagonal p6 mm to cubic Ia 3 ¯ d can be easily observed as the decrease of acid concentration and increase of temperature. The decrease of hydrophilic–hydrophobic ratio ( V H/ V L) of the mixed surfactant micelles favors the formation of the Ia 3 ¯ d mesophase. Furthermore, the Ia 3 ¯ d mesophase formed with 3.0 M HCl at 45 °C was found to possess a microtubule morphology with the diameter of 1–3 μm, the wall thicknesses of about 0.5 μm, and length up to hundreds of micrometers.

Microscopic location of photosensitive Malachite Green surfactant in mixed micelle and its photoinduced enhancement of solubilizing power

A Malachite Green derivative carrying a long alkyl chain affords photogenerated amphiphilicity by UV irradiation. The behavior of the photoresponsive Malachite Green surfactant was studied in mixed micelle solutions containing cetyltrimethylammonium chloride. We found that the Malachite Green surfactant increases the solubility of oily substance by UV irradiation. The role of the Malachite Green surfactant has been investigated by dynamic light scattering and spectroscopic analysis. The Malachite Green surfactant causes an increase in the micelle size, and its hydrophilic head group lies at the micellar interface. The mechanism of the photoinduced uptake of oily substances is discussed at the viewpoint of the microscopic location of the Malachite Green surfactant in the micelle.

Are the mixtures of homologous surfactants ideal?

The interaction between homologous surfactants in mixed micelles was studied by the Regular Solution Theory of mixed micelles. The interaction is independent of the nature of the polar head groups and attractive and the interaction parameter βM depends linearly on the difference in chain length ΔnC. The interaction becomes ideal at ΔnC=0.75±0.06. Above ΔnC≈5, the dependence remains linear but the slope increased 2.7 times. The phenomenon is explained as the effect of the reduction of the hydrocarbon/water micelle interface and a better packing of the chains in the micelle core, caused by the inclusion of a shorter homologous surfactants. This reduction can be more effective when ΔnC⩾5.

Surfactant/Nonionic Copolymer Interaction: A SLS, DLS, ITC, and NMR Investigation

The interactions between an oxyphenylethylene-oxyethylene nonionic diblock copolymer with the anionic surfactant sodium dodecyl sulfate (SDS) have been studied in dilute aqueous solutions by static and dynamic light scattering (SLS and DLS, respectively), isothermal titration calorimetry (ITC), and 13C and self-diffusion nuclear magnetic resonance techniques. The studied copolymer, S20E67, where S denotes the hydrophobic styrene oxide unit and E the hydrophilic oxyethylene unit, forms micelles of 15.6 nm at 25 degrees C, whose core is formed by the styrene oxide chains surrounded by a water swollen polyoxyethylene corona. The S20E67/SDS system has been investigated at a copolymer concentration of 2.5 g dm(-3), for which the copolymer is fully micellized, and with varying surfactant concentration up to approximately 0.15 M. When SDS is added to the solution, two different types of complexes are observed at various surfactant concentrations. From SLS and DLS it can be seen that, at low SDS concentrations, a copolymer-rich surfactant mixed micelle or complex is formed after association of SDS molecules to block copolymer micelles. These interactions give rise to a strong decrease in both light scattering intensity and hydrodynamic radius of the mixed micelles, which has been ascribed to an effective reduction of the complex size, and also an effect arising from the increasing electrostatic repulsion of charged surfactant-copolymer micelles. At higher surfactant concentrations, the copolymer-rich surfactant micelles progressively are destroyed to give surfactant-rich-copolymer micelles, which would be formed by a surfactant micelle bound to one or very few copolymer unimers. ITC data seem to confirm the results of light scattering, showing the dehydration and rehydration processes accompanying the formation and subsequent destruction of the copolymer-rich surfactant mixed micelles. The extent of interaction between the copolymer and the surfactant is seen to involve as much as carbon 3 (C3) of the SDS molecule. Self-diffusion coefficients corroborated light scattering data.