Surfactant Hydrocarbon Chain Research Articles

Coomassie Brilliant Blue G for Smart Colorimetric Determination of the Ionic Surfactants in Triton X-100 Solutions.

The conditions for the smart colorimetric determination of cetylpyridinium chloride and sodium dodecyl sulfate by reaction with Coomassie brilliant blue G (CBBG) have been proposed. The nature of the absorption and fluorescence spectra of aqueous solutions of CBBG as a function of acidity has been investigated. A variety of reagent forms and associations with ionic surfactants have been demonstrated. The composition of the associates formed in the CBBG-cationic surfactant system has been established. The increase in the analytical signal of the cationic surfactant and the stabilization of the colloid-chemical state of the system during reactions in the organized medium of the nonionic surfactant Triton X-100 has been demonstrated. These effects are realized through association in premicellar solutions and as a result of the solubilization of components in Triton X-100 micellar solutions. The addition of long-chain cationic surfactants to the reagent occurs with the replacement of the heteroatom proton. The absorption of CBBG-cationic surfactant associates solutions increases with the length of the cationic surfactant hydrocarbon chain. Ethanol additives decrease the aggregation of CBBG. The technique of cationic surfactant determination has been tested in the analysis of the pharmaceutical. The results show that the simplicity of analytical signal registration with satisfactory correctness and acceptably high sensitivity of determination is an advantage of the developed technique.

Cyclodextrin-Functionalized Iron Oxide Nanoparticles for Efficient Extractors of Gold and Silver Nanoparticles from Water

Extraction of Au/Ag nanoparticles (NPs) as nanometallic pollutants from an aqueous phase was carried out using cyclodextrin (CD)-stabilized magnetic NPs. It was driven by the host–guest interactions operating between the hydrocarbon chains of surfactants used for the colloidal stabilization of Au/Ag NPs and CD cavity of functionalized magnetic NPs. UV–visible studies based on the surface plasmon resonance of Au/Ag NPs helped us in quantitatively measuring the extraction. Dynamic light scattering studies determined the size and zeta potential (ζ) change during the extraction. Extraction clearly turned the colored Au/Ag NPs suspension into a colorless solution, indicating the formation of a Au/Ag–magnetic NPs complex. Elemental analysis of this complex by energy-dispersive spectrometry and X-ray photoelectron spectroscopy analyses indicated the presence of a high Fe/Au or Fe/Ag atomic ratio consumed to accomplish the extraction. Results showed that extraction very much depended on the strength of inclusion complex formation between the hydrocarbon chain of the surfactant and CD cavity immobilized on the Au/Ag and magnetic NPs’ surface, respectively. Stronger host–guest interactions were required to facilitate the extraction. This unique extraction methodology based on the host–guest interactions is considered to be a much better option for cleaning contaminated water from nanopollutants than conventional filtration techniques.

Nanostructuring with Surfactants: The Self-Assembly of a New Poly(thiophene-phenylene) Conjugated Polymer Bearing Azacrown Ether Pendant Groups.

We report the synthesis of a new conjugated polymer bearing crown ether moieties, poly[(N(1-aza-[18]crown-6)carbamido)thiophene-2,5-diyl-alt-1,4-phenylene] (BG2). In water, BG2 forms a dispersion with a slightly cloudy appearance. We have studied the effect of adding surfactants, with different polar head groups, on these polymer-polymer aggregates. Special attention is given to the system with the anionic surfactant, sodium dodecyl sulfate (SDS). The combination of photophysical techniques with electrical conductivity, NMR (1H, 13C, and 27Na), DFT calculations, molecular dynamics simulations, and small-angle neutron scattering (SANS) provides a detailed picture on the behavior of the SDS/BG2 system in aqueous solution and in thin films. NMR, electric conductivity, and DFT results suggest that hydrophilic interactions occur between the polar headgroup of the surfactant (OSO3- Na+) and the aza-[18]-crown-6 moiety. DFT calculations confirmed the capability of BG2 to form stable complexes with the Na+ cations, where the cation can be either inside the azacrown cavity or sandwiched between the cavity and the polymer chain, which seem to determine the position of the surfactant hydrocarbon chain and, therefore, be responsible for the disruption of the BG2 aggregates and subsequent increase in the photoluminescence quantum yields. SANS measurements, made with hydrogenated and deuterated SDS in D2O, clearly show how micron-sized aggregates of BG2 are broken down by SDS and then how BG2 becomes preferentially incorporated within joint colloidal particles of BG2 and SDS with increasing [SDS]/[BG2] molar ratio.

Sodium Cholate and Hexadecyl Trimethyl Ammonium Bromide or Dodecyl Trimethyl Ammonium Bromide Binary Mixed Micelles: Thermodynamic Properties and Thermodynamic Stabilization Influenced by the Cationic Surfactant Hydrocarbon Chain Length

Sodium Cholate and Hexadecyl Trimethyl Ammonium Bromide or Dodecyl Trimethyl Ammonium Bromide Binary Mixed Micelles: Thermodynamic Properties and Thermodynamic Stabilization Influenced by the Cationic Surfactant Hydrocarbon Chain Length

Geometric features in lyotropic liquid crystalline phase transitions observed in aqueous surfactant systems

Lyotropic liquid crystalline phases are widely known to be formed in aqueous surfactant mixtures. Although the phase behavior of several surfactants has been elucidated in the past years, a striking absence of detailed discussion on how molecular geometric parameters vary as different liquid crystals are formed is consistently seen in literature. The current work aimed to partially fill this gap, by determining how several structural parameters changed in a variety of phase transitions previously observed in aqueous surfactant binary and ternary mixtures. The main findings reveal that the cell parameter dimensions are strongly correlated with the packing fraction of small aggregates in each phase; the folding and interpenetration of surfactant hydrocarbon chains are most likely to happen in phases with lower curvature, and can greatly affect other structural parameters; added components can alter the aqueous surfactant phase behavior at different extents; and highly ordered phases are favored by a substantial decrease in the cross-sectional areas per surfactant; among others. The obtained results enable important knowledge on lyotropic liquid crystal formation, in addition to providing detailed information on how to control and obtain such phases, thus prospecting new insights in areas where they are highly desired.

Surface and Biocidal Properties of Gemini Cationic Surfactants Based on Propoxylated 1,6‐Diaminohexane and Alkyl Bromides

AbstractTwo new classes of gemini cationic surfactants—hexanediyl‐1,6‐bis[(isopropylol) alkylammonium] dibromide {in the abbreviation form: CnC6Cn[iPr‐OH] and CnC6Cn[iPr‐OH]2; alkyl: CnH2n + 1 with n = 9, 10, 12 and 14}—have been synthesized by interaction of alkyl bromides with N,N′‐di‐(isopropylol)‐1,6‐diaminohexane and N,N,N′,N′‐tetra‐(isopropylol)‐1,6‐diaminohexane. The surface tension, electrical conductivity, and dynamic light scattering (DLS) techniques were used to investigate the aggregation properties of the gemini cationic surfactants in aqueous solution. The formation of critical aggregates at two concentrations in an aqueous solution from obtained gemini cationic surfactants were determined via the tensiometric method. Thus, these gemini cationic surfactants start to form aggregates at concentrations well below their critical micelle concentrations (CMC). The surface properties and the binding degree (β) of the opposite ion were tested against the length of the surfactant hydrocarbon chain and the number of the isopropylol groups in the head group. By applying the DLS technique, it was explored that how the number of isopropylol groups in gemini cationic surfactants with C12H25 chain affects the sizes of micelles at concentrations greater than CMC. It was discovered that the obtained gemini cationic surfactants have a biocidal character.

A series of nonionic surfactants for lignite flotation and adsorption performance

ABSTRACT Nonionic surfactants have been applied to improve the lignite floatability in the flotation process. In this paper, Inner Mongolia lignite was pretreated by three type surfactants, including sorbitan monolaurate, sorbitan monostearate, and sorbitan monooleate, respectively. It was investigated that the effect of the length and saturability of hydrocarbon chain on the collectivity and selectivity of surfactant. The flotation results indicated that the optimum efficiencies were found at the dosages of about 35 kg/t for the three surfactants. However, the recovery of combustible material of lignite pretreated by sorbitan monolaurate is comparatively low, which may relate to the weak collectivity of this shorter hydrocarbon chain surfactant. On the other hand, XPS results showed that the C1s can be fitted to C-C, C-H, C-O, and COO- with the contents of 10.99%, 9.19% and 2.11% on the raw lignite surface, respectively. After the pretreatment, the contents of hydrophobic C-C, C-H were increased to 13.53%, 16.07% and 17.18% for the three surfactants. Obviously, the hydrophobic functional groups were much higher after pretreated by sorbitan monooleate, which was corresponded with the better flotation results. Therefore, the longer and unsaturated hydrocarbon chain in sorbitan monooleate molecule is beneficial for the collectivity and selectivity for lignite.

Cationic Surfactant-Induced Formation of Uniform Gold Nanoparticle Clusters with High Efficiency of Photothermal Conversion under Near-Infrared Irradiation.

A novel and simple method for the fabrication of gold nanoparticle (AuNP) clusters was introduced for use as an efficient near-infrared (NIR) photothermal agent. Cationic surfactants were employed to assemble AuNPs into clusters, during which polyvinylpyrrolidone (PVP) was used to stabilize the AuNP clusters. Through this manner, AuNP clusters with a uniform shape and a narrow size distribution (55.4 ± 5.0 nm by electron microscope) were successfully obtained. A mechanism for the formation of AuNP clusters was studied and proposed. Electrostatic interactions between AuNPs and cationic surfactants, hydrophobic interactions between hydrocarbon chains of cationic surfactants, and repulsive steric interactions of PVP were found to play an important role with regard to the formation mechanism. Photothermal effect in the NIR range of the AuNP clusters was demonstrated; results presented a highly efficient photothermal conversion (with a maximum η of 65%) of the AuNP clusters. The clusters could be easily coated by a silica layer, enabling their biocompatibility and colloidal stability in physiological fluids. The easy-to-fabricate AuNP clusters showed high potential of use as an NIR photothermal agent for cancer therapy.

The Nucleation and Growth of Succinic Acid in the Presence of Surfactants

AbstractImpurities may have a marked effect on crystal nucleation and growth. To further understand the role of impurities, the crystallization (solubility, nucleation, growth) of succinic acid in water in the presence of surfactants such as polyethylene glycol sorbitan monooleate (Tween 80), cetyltrimethylammonium bromide (CTAB) and sodium dodecylbenzenesulfonate (SDBS) was investigated experimentally. The presence of CTAB, SDBS or Tween 80 had little influence on succinic acid solubility but did slow crystallization kinetics. The surfactant monomer in solution, not micelles, proved to play the primary role affecting nucleation. The nucleation inhibition by surfactant was analyzed on the base of a two‐step nucleation process: (1) the inhibition on the formation and growth of succinic acid nanodroplets and (2) the influence on succinic acid single nucleus (SASN) in secondary nucleation. SASN may play important role in secondary nucleation, although further work is necessary to conform this. The length of the surfactant hydrocarbon chain was found to affect crystal habit development.

A molecular‐thermodynamic approach to predict the micellization of binary surfactant mixtures containing amino sulfonate amphoteric surfactant and nonionic surfactant

A molecular‐thermodynamic approach was adopted to predict the value of mixed critical micelle concentration (cmc) for the binary surfactant mixtures constituted by an amino sulfonate amphoteric surfactant, sodium 3‐(N‐dodecyl ethylenediamino)‐2‐hydropropyl sulfonate (abbr. C12AS), and a nonionic surfactant, octylphenol polyethylene ether (OP‐n, where n denotes the average number of oxyethylene glycol ether). In this investigation, considering two positive charges on the hydrophilic group of C12AS, which is unlike to conventional zwitterionic surfactants having one positive charge (such as, alkylbetaine, etc.), three schemes were designed to obtain the geometric parameter describing the dipole structure of C12AS. According to the selected optimum scheme, four cases corresponding to the different conformations of both the headgroup and the hydrocarbon chain of surfactant were discussed. The results show that the predicted value of mixed cmc for the C12AS/OP‐n mixtures agrees well with the experiment value. The deviation of the predicted value from the experimental value can be explained by the effect of the hydrophilicity of OP‐n on the process of micellization. © 2017 American Institute of Chemical Engineers AIChE J, 2017

Hexadecane-in-water emulsions as thermal-energy storage and heat transfer fluids: Connections between phase-transition temperature and period of hexadecane droplets dispersed in hexadecane-in-water emulsions and characteristics of surfactants

Colloidal stability and fluidity of organic phase change material (OPCM)-in-water emulsions (OPCM/W) against temperature change and supercooling (solidifying-temperature; Ts) of OPCM droplets in OPCM/W emulsions were examined to develop the thermal-energy storage and heat transfer fluids of OPCM/W emulsions. Higher colloidal stability and fluidity of OPCM/W emulsions against temperature change in the range of −1–40°C were achieved by decrease in the droplet size below ∼2μm in diameter. Furthermore, the solidifying-temperature (Ts) of OPCM droplets in OPCM/W emulsions increased with longer hydrocarbon chain length of surfactants. Consequently, the solidifying-period (ts) of OPCM droplets in the OPCMW emulsion was shortened with longer hydrocarbon chain length of surfactants. On the other hand, Pluronic-type surfactants with poly(propylene oxide) as a hydrophobic part did not affect Ts and ts of OPCM droplets in the emulsions. These indicate that hydrocarbon chain of surfactants acts as nuclei in the droplets to promote the solidification of OPCM droplets in OPCM/W emulsions. We also revealed that the precipitation of surfactants in OPCM/W emulsions promotes the solidification of OPCM droplets in OPCM/W emulsions. So, the nucleation of OPCM in droplets by hydrocarbon chain and precipitation of surfactants in OPCM/W emulsions prevents the supercooling of OPCM droplets in OPCM/W emulsions.

Double-Tailed Cystine Derivatives as Novel Substitutes of Phospholipids with Special Reference to Liposomes.

Cystine-based gemini surfactants with dodecyl, tetradecyl, hexadecyl, and octadecyl hydrocarbon chains were synthesized, and their interactions with unsaturated (soy phosphatidylcholine, SPC)/saturated (hydrogenated SPC, HSPC) soy phosphatidylcholines in the forms of a monolayer and a model liposome were estimated for different combinations of the components in the mixed systems. Studies of Langmuir monolayers at the air-aqueous buffer interface revealed condensation of the monomolecular films with the addition of surfactants. The effect of surfactants decreased according to the following order: octadecyl > hexadecyl > tetradecyl > dodecyl homologs. The nonideal mixing between the components was estimated using the deviation of the experimental molecular area from the ideal area per molecule. The excess molecular area increased with the increase in the surfactant chain length and phospholipid saturation. The 50 mol % mixture of cystine derivatives and phospholipids formed thermodynamically stable monolayers. The surfactants increased the rigidity of SPC monolayers and decreased that of HSPC monolayers, as observed by the studies of surface dialational rheology. The film structure at the air-water interface could differentiate the SPC- and HSPC-comprising systems through the formation of organized regions, especially at a higher surface pressure. The constriction of surfactant/phospholipid hybrid vesicles was observed with an increase in the length of surfactant hydrocarbon chains. The negative zeta potential of vesicles took the highest values and did not change with time for 20 and 50 mol % surfactant. The spherical shape of the vesicles was confirmed by transmission electron microscopy. Differential scanning calorimetry revealed an increase in fluidity of HSPC bilayers and rigidity of SPS bilayers under the influence of surfactants. These effects were confirmed by fluorescence spectroscopy. All of the vesicle formulations were found to be nontoxic from the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide assay, suggesting their potential as a novel membranous system for the delivery of drugs, genetic materials, vaccines, and other therapeutic agents.

Selective Antimicrobial Activities and Action Mechanism of Micelles Self-Assembled by Cationic Oligomeric Surfactants.

This work reports that cationic micelles formed by cationic trimeric, tetrameric, and hexameric surfactants bearing amide moieties in spacers can efficiently kill Gram-negative E. coli with a very low minimum inhibitory concentration (1.70-0.93 μM), and do not cause obvious toxicity to mammalian cells at the concentrations used. With the increase of the oligomerization degree, the antibacterial activity of the oligomeric surfactants increases, i.e., hexameric surfactant > tetrameric surfactant > trimeric surfactant. Isothermal titration microcalorimetry, scanning electron microscopy, and zeta potential results reveal that the cationic micelles interact with the cell membrane of E. coli through two processes. First, the integrity of outer membrane of E. coli is disrupted by the electrostatic interaction of the cationic ammonium groups of the surfactants with anionic groups of E. coli, resulting in loss of the barrier function of the outer membrane. The inner membrane then is disintegrated by the hydrophobic interaction of the surfactant hydrocarbon chains with the hydrophobic domains of the inner membrane, leading to the cytoplast leakage. The formation of micelles of these cationic oligomeric surfactants at very low concentration enables more efficient interaction with bacterial cell membrane, which endows the oligomeric surfactants with high antibacterial activity.

Role of surfactant head group and chain length in aqueous lubrication: Steel−steel contact

Surfactants are important molecules to decide the lubricating characteristics in aqueous lubrication. In metal working fluids, stabilization of oil droplets in continuous water phase is aided by repulsive force created by surfactants at oil−water interface. Present study explores the possibility of participation of surfactants molecules in lubrication process. Effect of surfactant hydrocarbon chain length and type of head group in aqueous lubrication is explored. Aqueous solutions were prepared using Oleic acid, Tween 20 and Tween 80 surfactants. Goniometer was used for recording surface and interfacial effects of surfactants in water and on steel substrate. Lubricating response of aqueous solutions of surfactants was recorded using Tribometer. Ability of a surfactant to adsorb the steel surface along with longer hydrocarbon chain length is well suited for aqueous lubrication. Solubility of surfactant in water is another important parameter.

Hydrophobic flocculation of talc with kerosene and effects of anionic surfactants

ABSTRACTThe variation of the hydrophobic flocculation behavior of talc mineral with pH, kerosene concentration, stirring speed, flocculation, and settling times was investigated. The experimental studies showed that the flocculation of talc suspension increased to a particular point with increasing kerosene concentration and thereafter decreased slightly. Also, the flocculation with kerosene was not much affected by the pH changes of the suspension. On the other hand, sodium oleate, sodium dodecyl sulfate (SDS), and Aero 801 used as anionic surfactant in conjunction with kerosene provided significant increases in the flocculation of talc, and depends on increasing surface hydrophobicity of the particles. Especially, in the presence of sodium oleate along with kerosene, the talc suspension could be flocculated with a recovery of 95%. Consequently, the enhancement with nonpolar oil was more significant for the hydrophobic flocculation of talc suspension promoted by long hydrocarbon chain surfactant (sodium oleate) than short hydrocarbon chain surfactants (SDS and Aero 801).

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.

On the growth of pneumatic foams

This work reports on the behaviour of tenacious and transient pneumatic foams produced at large range of values of gas delivery rates (or superficial velocities) and surface tensions. Experimental data from the literature and produced in the course of this study were processed and analyzed. The tenacious foams were stabilized via Polyoxiethylene-2 sulfate (SDP(2)S) in presence of 0.024M NaCl and 0.003M AlCl(3) ( CMC = 1.83×10(-2) M) in the concentration range of 3.33×10(-3) M to 3.8×10(-2) M (0.18CMC -2.08CMC corresponding to values of the dynamic surface tension in the range of 42.7mN/m to 37.5mN/m. The range of gas delivery rates was from 20.5ml/min to 482.8ml/min. It was found out that the rate of foam generation coincides with the gas delivery rate until a certain critical value of the latter, beyond which the rate of foam growth exceeds the rate of gas delivery. The level of this exceeding depends on the dynamic surface tension. The lower the value of the dynamic surface tension the larger the level of this exceeding. This rule was found valid until a certain upper limit of the gas delivery rate, at which the dependence on the dynamic surface tension ceases to exist. The second set of experiments was conducted on transient foams. The latter were stabilized by three members of homologue surfactants series: sodium octylsulfate (SOS), sodium decylsulfate (SDeS), and sodium dodecylsulfate (SDS) in the concentration range of 0.01CMC -0.1CMC corresponding to 72.75mN/m to 68.18mN/m. The aqueous solutions of the three surfactant homologues had identical values of static surface tension at the same ratio C/CMC . Bikerman's "unit of foaminess" was measured for each particular case. It was shown that at identical equilibrium surface tensions both the foaminess and the rate of foam decay increase upon lengthening of the surfactant's hydrocarbon chain. It was indicated as well that the foaminess increases linearly upon raising the gas delivery rate until a certain critical value, above which substantial increase is observed. It was finally concluded that both the tenacious and the transient foams have completely different behaviour. For this reason they should be modeled separately but more experimental data are still needed.

Quiescent bilayers at the mica–water interface

Despite extensive studies with many experimental techniques, the morphology and structure of the self-assembled aggregates of quaternary alkyl ammonium bromides (CnTABs; where n denotes the number of hydrocarbons in the surfactant tail) at the solid–liquid interface remains controversial, with results from atomic force microscopy (AFM) imaging pointing to a variety of surface aggregates such as cylinders and surface micelles, whilst surface force measurements and neutron reflectivity (NR) measurements reporting bilayer structures. Using a home-built liquid cell that employs the “bending mica” method, we have performed unprecedented synchrotron X-ray reflectometry (XRR) measurements to study the adsorption behaviour of a CnTAB series (n = 10, 12, 14, 16 and 18) at the mica–water interface at different surfactant concentrations. We find that our XRR data cannot be described by surface aggregates such as cylindrical and spherical structures reported by AFM studies. In addition we have observed that the bilayer thickness, surface coverage and the tilt angle all depend on the surfactant concentration and surfactant hydrocarbon chain length n, and that the bilayer thickness reaches a maximum value at approximately the critical micellisation concentration (∼1 cmc) for all the CnTABs investigated. We propose that CnTABs form disordered bilayer structures on mica at concentrations below cmc, whilst at ∼1 cmc they form more densely packed bilayers with the tails possibly tilted at an angle θt ranging from ∼40 to 60° with respect to the surface normal in order to satisfy the packing constraints due to the mica lattice charge, i.e. so that the cross-section area of the tilted chain would match that of the area of the lattice charge (As ≅ 46.8 Å2). As the surfactant concentration further increases, we find that the bilayer thickness decreases, and we ascribe this to the desorption of surfactant molecules, which recovers certain disorder and fluidity in the chain and thus leads to interdigitated bilayers again. In light of our XRR results, previously unattainable at the mica–water interface, we suggest that the surface aggregates observed by AFM could be induced by the interaction between the scanning probe and the surfactant layer, thus representing transient surface aggregation morphologies; whereas the CnTAB bilayers we observe with XRR are intrinsic structures under quiescent conditions. The suggestion of such quiescent bilayers will have fundamental implications to processes such as lubrication, self-assembly under confinement, detergency and wetting, where the morphology and structure of surfactant layers at the solid–liquid interface is an important consideration.

Analysis of interfacial and micellar behavior of sodium dioctyl sulphosuccinate salt (AOT) with zwitterionic surfactants in aqueous media

The interfacial and bulk properties of mixtures of the anionic surfactant (dioctyl sulphosuccinate sodium salt, AOT) with zwitterionic surfactants 3-(N,N-dimethyldodecylammonio) propane sulfonate (DPS), 3-(N,N-dimethyltetradecylammonio) propane sulfonate (TPS), 3-(N,N-dimethylhexadecylammonio) propane sulfonate (HPS) have been studied employing surface tension, fluorescence, and viscometric techniques in aqueous media at 25 °C. It is observed that these mixtures exhibit synergism and these synergistic interactions increase with the enhancement of the hydrocarbon chain of the zwitterionic surfactant. The various physicochemical properties such as critical micelle concentration (cmc), surface excess concentration ( Г max), minimum area per molecule ( A min), aggregation number ( N agg), interaction parameters ( β σ , β m ), and thermodynamic parameters such as standard Gibbs free energy of adsorption (Δ G ads o ), excess free energy of micellization (Δ G ex), and standard Gibbs free energy of micellization (Δ G m o ) have been evaluated. The negative values of Δ G m o and Δ G ads o show that the micelle formation and adsorption of surfactant at the air/solution interface is energetically favorable, while a negative value of Δ G ex ensures stability of the mixed micelles formed. The Regular Solution Approximation, Motomura and Rosen’s approaches have been used to explain and compare the results. The packing parameter ( p) ensures the formation of vesicles or bilayers for AOT + DPS/TPS mixtures, which can potentially be used as delivery agents for industrial applications.

Aggregation behavior of nonionic surfactants in ionic liquid mixtures

We investigated the aggregation behavior of polyoxyethylene (POE)-type nonionic surfactants in ionic liquid mixtures composed of 1-ethyl- and 1-hexyl-3-methylimidazolium tetrafluoroborates (emimBF 4 and hmimBF 4, respectively) by means of 1H NMR chemical shift analysis and dynamic light-scattering measurements. The surfactants do not aggregate in hmimBF 4, whereas they are essentially immiscible with emimBF 4. That is, the surfactants are highly solvophilic to hmimBF 4, while are highly solvophobic to emimBF 4. In mixtures of emimBF 4 and hmimBF 4 micellization was observed. The critical micelle concentration (cmc) decreased and the mean hydrodynamic diameter of micelles, and hence, the micellar aggregation number, increased with increase in mole fraction of emimBF 4 in the ionic liquid mixture. 1H NMR chemical shift analysis revealed that hmimBF 4 interacts with surfactant molecules preferentially in the ionic liquid mixture through interaction of hexyl groups with the surfactant hydrocarbon chains. The present work demonstrates that solvent quality can be controlled by mixing two ionic liquids to induce self-aggregation of amphiphilic molecules.