A Study of the Solubilization of Polar Oily Materials by Alkyl Polyglucoside and Sodium Dodecyl Sulfate in Mixed Surfactant System

The effects of different alkyl chains of nonionic surfactants and solubilized polar oily material on the solubilizing capacity of binary anionic‐nonionic mixed surfactant systems were studied. This system includes surface tension measurements to determine the critical micelle concentration. Results were analyzed using regular solution theory to obtain the mixed micelle and the interaction parameter β, in order to evaluate the type of interactions of surfactants in the mixed micelle. Solubilizing capacity has been investigated by measuring the optical density of solubilized polar oily materials like octanol, decanol, and dodecanol. The solubilizing phenomenon exhibited by mixed surfactants systems showed better results than that of the individual surfactant system. The amount of solubilization in mixed surfactant increases with increase in carbon chain length of alkyl polyglucoside.     

Fading phenomena of azo oil dye in anionic-nonionic surfactant solutions II. Effects of alkyl and/or oxyethylene groups in nonionic surfactant on the fading rate

The effects of alkyl and/or oxyethylene groups in a nonionic surfactant on the fading phenomena of 4-phenylazo-1-naphthol (4-OH), which occur in aqueous solutions of anionic-nonionic surfactant systems, are described; these systems are sodium dodecyl sulfate (SDS) — alkyl poly(oxyethylene) ethers (C_mPOE_n, m=12,14,16, and 18 at n=20; n=10, 20, 30, and 40 at m=16). The fading phenomenon is observed when 4-OH is added to the anionic-nonionic mixed surfactant solutions at a molar ratio of 11. A singlet oxygen, which is caused by the hydrophilic-hydrophilic interaction between two surfactants, is thought to attack the tautomer of 4-OH. The fading rate of 4-OH accelerates with increasing alkyl chain length or with decreasing oxyethylene chain length in the nonionic surfactant molecule. The effect on the fading behavior of 4-OH would be larger for a system which can easily form a mixed micelle than for a system in which two kinds of micelles coexist.     

The structure of mixed nonionic surfactant monolayers at the air-water interface: the effects of different alkyl chain lengths

The structure of mixed nonionic surfactant monolayers of monodecyl hexaethylene glycol (C10E6) and monotetradecyl hexaethylene glycol (C14E6) adsorbed at the air-water interface has been determined by specular neutron reflectivity. Using partial isotopic labeling (deuterium for hydrogen) of the alkyl and ethylene oxide chains of each surfactant, the distribution and relative positions of the chains at the interface have been obtained. The packing of the two different alkyl chain lengths results in structural changes compared to the pure surfactant monolayers. This results in changes in the relative positions of the alkyl chains and of the ethylene oxide chains at the interface. The role of the alkyl chain length is contrasted with that of the ethylene oxide chain length, determined from results reported previously on the nonionic surfactant mixture of monododecyl triethylene glycol (C12E3) and monododecyl octaethylene glycol (C12E8).     

Structure of nonionic surfactant micelles in the ionic liquid ethylammonium nitrate

The structure of micelles formed by nonionic polyoxyethylene alkyl ether nonionic surfactants, C n E m , in the room-temperature ionic liquid, ethylammonium nitrate (EAN), has been determined by small-angle neutron scattering (SANS) as a function of alkyl and ethoxy chain length, concentration, and temperature. Micelles are found to form for all alkyl chains from dodecyl through to octadecyl. Dodecyl-chained surfactants have high critical micelle concentrations, around 1 wt%, and form weakly structured micelles. Surfactants with longer alkyl chains readily form micelles in EAN. The observed micelle structure changes systematically with alkyl and ethoxy chain length, in parallel with observations in aqueous solutions. Decreasing ethoxy chain length at constant alkyl chain length leads to a sphere to rod transition. These micelles also grow into rods with increasing temperature as their cloud point is approached in EAN.     

Microcalorimetric study on micellization of nonionic surfactants with a benzene ring or adamantane in their hydrophobic chains

The micellization of a novel family of nonionic surfactants poly(oxyethylene) glycol alkyl ethers has been studied by microcalorimetry. One of the surfactants has adamantane, and the other nonionic surfactants have a benzene ring in their hydrophobic chains, which moves from the terminal of the hydrophobic chain toward the headgroup. Moreover, the alkyl chain of the nonionic surfactants is straight or branched. Both the critical micelle concentration (cmc) and the thermodynamic parameters associated with the micelle formation have been obtained. The cmc decreases and the enthalpy of micelle formation (deltaH(mic)) becomes less positive gradually as the length of hydrophobic chain increases, whereas the values of cmc and deltaH(mic) tend to increase for the surfactants with a longer ethylene oxide chain. However, the deltaH(mic) value of the surfactant with seven carbon atoms in a hydrophobic chain is more positive than that of the surfactant with six carbon atoms in a hydrophobic chain. Comparing with the nonionic surfactant with a methylene hydrophobic chain, the surfactants with benzene rings and adamantane groups have larger cmc values and the cmc values increase with the size of the groups. Furthermore, moving the phenyl group from the terminal of the hydrophobic chain to the neighbor of the hydrophilic headgroup leads to the decreased cmc. Both the variation of hydrophobic interaction from the movement of phenyl group and pi-pi interaction among adjacent phenyl groups affect deltaH(mic) values.     

Interfacial and Thermodynamic Properties of Anionic‐Nonionic Mixed Surfactant System: Influence of Hydrophobic Chain Length of the Nonionic Surfactant

The influence of hydrophobic chain length in nonionic surfactants on interfacial and thermodynamics properties of a binary anionic‐nonionic mixed surfactant was investigated. In this study, nonionic surfactants lauric‐monoethanolamide (C₁₂ MEA) and myrisitic‐monoethanolamide (C₁₄ MEA) were mixed with an anionic surfactant, α‐olefin sulfonate (AOS). The critical micelle concentration (cmc), maximum surface excess (Γ_max), and minimum area per molecule (A_min) were obtained from surface tension isotherms at various temperatures. The thermodynamic parameters of micellization and adsorption were also computed. Micellar aggregation number (N_agg), micropolarity, and binding constant (K_sv) of pure and mixed surfactant system was calculated by fluorescence measurements. Rubingh's method was applied to calculate interaction parameters for the mixed surfactant systems.     

低碳醇对季铵盐二聚表面活性剂C_(12)-2-C_(12)·2Br胶团化行为的影响

随着丙、丁、戊、已醇的加入，与季铵盐二聚表面活性剂C_(12)-2-C_(12)· 2Br组成了混合胶团，醇分子以烷烃链插入胶团中，羟基则位于胶团栅栏层处。这 减弱了表面活性剂离子头基间的静电排斥力，使临界胶团浓度(cmc)降低，同时使 胶团表面反离子解离度增大。随着醇分子的烷烃链增长，这种影响更为显著。     

MICELLE FORMATION IN MIXTURES OF ANIONIC AND NONIONIC SURFACTANTS

The critical micelle concentration of mixtures of anionic and nonionic surfactants was measured. The anionic surfactants were alkylbenzene sulfonates and the nonionic surfactants were polyoxyethylene nonylphenols and a polyoxy-ethylene alcohol. The effect of added electrolyte, the number of ethylene oxide units in the polyethoxylate, and the anionic alkyl chain length were studied. All systems showed substantial negative deviations (lower CMC) from ideal solution theory. The results can be represented by regular solution theory. Charge separation appears to be the source of the nonideality. This considers the reduction of electrostatic repulsion between the ionic surfactant head groups in the mixed micelle, due to the insertion of nonionic hydrophilic groups between these charged groups, to be the cause of enhanced micelle formation. The physical basis of regular solution theory was shown to be consistent with the charge separation effect.     

Anionic–Nonionic Mixed Surfactant Systems: Micellar Interaction and Thermodynamic Behavior

The interactions between an anionic surfactant, viz., sodium dodecylbenzenesulfonate and nonionic surfactants with different secondary ethoxylated chain length, viz., Tergitol 15-S-12, Tergitol 15-S-9, and Tergitol 15-S-7 have been studied in the present article. An attempt has also been made to investigate the effect of ethoxylated chain length on the micellar and the thermodynamic properties of the mixed surfactant systems. The micellar properties like critical micelle concentration (CMC), micellar composition (X_A), interaction parameter (β), and the activity coefficients (f_A and f_NI) have been evaluated using Rubingh's regular solution theory. In addition to micellar studies, thermodynamic parameters like the surface pressure (Π_CMC), surface excess values (Γ_CMC), average area of the monomers at the air–water interface (A_avg), free energy of micellization (ΔG_m), minimum energy at the air–water interface (G_min), etc., have also been calculated. It has been found that in mixtures of anionic and nonionic secondary ethoxylated surfactants, a surfactant containing a smaller ethoxylated chain is favored thermodynamically. Additionally, the adsorption of nonionic species on air/water interface and micelle increases with decreasing secondary ethoxylated chain length. Dynamic light scattering and viscometric studies have also been performed to study the interactions between anionic and nonionic surfactants used.     

混合反胶束的电导与微结构研究

反胶束是两亲分子在非极性溶剂中形成的一种有序组合体，在医药、化工、采油、胶束催化及酶催化等领域中有重要应用．与胶束溶液相比，人们对反胶束的形成与结构的了解至今仍不充分．特别是对于由混合表面活性剂形成的反胶束的研究几乎无人涉及．本文采用动态光散射、电导及荧光光谱等手段对阴离子表面活性剂AOT与非离子表面活性剂形成的混合反胶束进行了研究，旨在探讨利用表面活性剂的复配来调节和控制反胶束的结构和性能．亚实验部分二异辛基磺化琉璃酸钠（AOT，Sigma公司）；Brij30为含4个氧乙烯基（EO基）的十二碳醇（AcrosOrgani…     

Effect of alkyl chain length and size of the headgroups of the surfactant on solvent and rotational relaxation of Coumarin 480 in micelles and mixed micelles

The effect of alkyl chain length and size of the headgroups of the surfactant on the solvation dynamics and rotational relaxation of Coumarin 480 (C-480) has been investigated using dynamic Stokes' shift of C-480 in different types of alkyltrimethylammonium bromide micelles and mixed micelles. The rotational relaxation time increases with increase in alkyl chain length of the surfactant. The increase in the number of alkyl chains of the surfactant leads to the more close packed micelles, hence the microviscosity of the micelles increases and consequently rotational relaxation time increases. Solvation time also increases due to the increase in number of alkyl chains of the surfactant. The change in solvation and rotational relaxation time is more prominent in micelles compared to mixed micelles. The solvation and rotational relaxation time also increase with the increase in size of the headgroup of the surfactant.     

Influence of alkyl chain length of alpha olefin sulfonates on surface and interfacial properties

Alpha olefin sulfonates (AOS) with various alkyl chain lengths have been used to investigate the influence of alkyl chain length on the interfacial properties at air–water, liquid paraffin–water, and parafilm–water interfaces. It was found that the critical micelle concentration decreased with increasing alkyl chain length, while the efficiency of reducing surface tension was inverse relationship with alkyl chain length. The diffusion coefficient obviously reduced with an increase of surfactant concentration and alkyl chain length. The C_14-16AOS shows better wettability and emulsification than C_16-18AOS and C_20-24AOS. For foaming properties, the foamability and foam stability dramatically decreased with increasing alkyl chain length.     

Synergism in mixtures of n-octyl-β-d-thioglucoside and different n-alkyltrimethylammonium bromides: effect of the alkyl chain length

Mixtures of n-octyl-β-d-thioglucoside with three different n-alkyltrimethylammonium bromides (n?=?12 (DTAB), 14 (TTAB), and 16 (CTAB)) have been studied by using fluorescence spectroscopic techniques. The critical micelle concentration values of pure and mixed systems were determined by the pyrene 1:3 ratio method. The experimental results were treated by using thermodynamic mixing approaches based on the pseudophase separation model. It was found that all the mixed systems show a negative deviation from ideal behavior, more pronounced as the larger the alkyl tail of the co-surfactant. It was also observed that the three mixed systems fulfill the conditions of synergism, this behavior being also dependent on the alkyl chain length. By using the static quenching method, the mean micellar aggregation numbers of mixed micelles were obtained. In all the cases, it was observed that the aggregation number is initially reduced with the participation of the cationic surfactant, remaining almost constant and close to the aggregation number of the pure cationic micelles. The local viscosity of pure and mixed micelles was examined by the photophysical response of the hydrophobic probe coumarin 6 solubilized in the micellar medium. It was found that the participation of the ionic component induces the formation of a less ordered structure than that of pure nonionic micelles. This effect being less pronounced as the chain hydrocarbon length of the co-surfactant increases.     

Calorimetric study on the temperature dependence of the formation of mixed ionic/nonionic micelles

The differential excess enthalpy of mixed micelle formation was measured at different temperatures by mixing nonionic hexa(ethylene glycol) mono n-dodecyl ether with anionic sodium dodecyl sulfate or cationic dodecylpyridinium chloride. The experimental data were obtained calorimetrically by titrating a concentrated surfactant solution into a micellar solution of nonionic surfactant. The composition and the size of the mixed nonionic/ionic micelles at different surfactant concentrations were also determined. Pronounced differences in both composition and excess enthalpy were found between the anionic and the cationic mixed system. For both systems, the excess enthalpies become more exothermic with increasing temperature, but for the anionic mixed system an additional exothermic contribution was found which was much less temperature dependent. Temperature dependence of the excess enthalpy was attributed to the effect of the ionic headgroup on the hydration of the ethylene oxide (EO) groups in the mixed corona. Ionic headgroups located in the ethylene oxide layer cause the dehydration of the EO chains resulting in an additional hydrophobic contribution to the enthalpy of mixing. A high affinity of sodium dodecyl sulfate for nonionic micelles and an extra exothermic and less temperature dependent contribution to the excess enthalpy found for the SDS-C(12)E(6) system might be attributed to specific interactions (hydrogen bonds) between the sulfate headgroup and the partly dehydrated EO chain.     

Pseudo-homogeneous micelle extraction of ion-associates formed between tetrabutylammonium ion and some aromatic sulfonate ions into nonionic surfactant micelle studied through the mobility measurements in capillary zone electrophoresis

Ion-association extraction of some aromatic sulfonate ions including alkylbenzene sulfonates with tetrabutylammonium ion (TBA+) into nonionic surfactant micelle has been investigated through the changes in the electrophoretic mobility. Nonionic surfactants of Brij 35 and Brij 58 were used as micelle substrates to which the ion-associates formed could distribute. The electrophoretic mobility of the aromatic sulfonate ions was measured by capillary zone electrophoresis in the presence of TBA+ and/or the nonionic surfactant to determine ion-association constants (K(ass)), binding constants of the anions to the nonionic surfactant micelle (K(B)), and binding constants of the ion-associates to the nonionic surfactant micelle (K(B,IA)). Nonlinear phenomena induced with the alkyl chain moiety were observed on K(ass) and K(B) by its linear structure and the mixed micelle formation, respectively. Larger K(B) values were obtained with Brij 58 as micelle matrix than with Brij 35, while the differences in K(B,IA) were small between Brij 58 and Brij 35.     

Effect of the surfactant alkyl chain length on the stabilisation of lyotropic nematic phases

Lyotropic quaternary mixtures of potassium alkanoates (KCx) and sodium alkyl sulphates (NaCxS), where x is the number of carbon atoms in their alkyl chains, were prepared to investigate the effect of the surfactant alkyl chain length on the stabilisation of lyotropic nematic phases. The lyotropic mixtures investigated were formed by the dissolution of KCx (NaCxS) surfactants in the mixture of Rb₂SO₄/1-decanol/water (Na₂SO₄/1-decanol/water), separately. The uniaxial-to-biaxial nematic phase transitions were identified from the temperature dependence of the birefringences of the nematic phases by means of laser conoscopy. The micelle dimensions were obtained from small-angle X-ray scattering measurements. It was observed that the increase in the surfactant alkyl chain length causes the micellar growth in the plane perpendicular to the main amphiphile bilayer. The surfactant alkyl chain length plays a key role on the shape anisotropy of micelles, which triggers the orientational fluctuations that are responsible for the stabilisation of the different lyotropic nematic phases.     

Solubilization properties of aqueous solutions of alkyltrimethylammonium halides toward a water-insoluble dye

The solubility of a water-insoluble dye, Sudan Red B, in aqueous sodium halide solutions of tetradecyl-, cetyl-, and stearyltrimethylammonium halides has been measured at different surfactant and salt concentrations, and the dependence of solubilization properties on alkyl chain length has been discussed with reference to the micelle size and shape. At low ionic strengths where only spherical micelles exist, the solubilization power of micellar surfactant slightly increases with increasing the ionic strength, but it sharply increases at high ionic strengths above the threshold value of sphere-rod transition. However, the solubilization power becomes independent of the ionic strength, if their rodlike micelles are sufficiently long. The solubilization capacity increases linearly with increasing the molecular weight, almost independent of counterion species, but the rod-like micelle has a higher solubilization capacity than the spherical micelle. The solubilization capacity is larger for a surfactant with longer alkyl chain, indicating that the dye is solubilized more readily in a larger hydrophobic core. The solubilized dye is situated in a rodlike micelle of alkyltrimethylammonium halides, on average, 4.5–7.5 nm apart from each other.     

Properties of mixed micelles of cationic gemini surfactants and nonionic surfactant triton X-100: effects of the surfactant composition and the spacer length

The mixed micelles of cationic gemini surfactants C12C(S)C12Br2 (S=3, 6, and 12) with the nonionic surfactant Triton X-100 (TX100) have been studied by steady-state fluorescence, time-resolved fluorescence quenching, electrophoretic light scattering, and electron spin resonance. Both the surfactant composition and the spacer length are found to influence the properties of mixed micelles markedly. The total aggregation number of alkyl chains per micelle (N(T)) goes through a minimum at X(TX100)=0.8. Meanwhile, the micropolarity of the mixed micelles decreases with increasing X(TX100), while the microviscosity increases. The presence of minimum in N(T) is explained in terms of the competition of the reduction of electrostatic repulsion between headgroups of cationic gemini surfactant with the enhancement of steric repulsion between hydrophilic headgroups of TX100 caused by the addition of TX100. The variations of micropolarity and microviscosity indicate that the incorporation of TX100 to the gemini surfactants leads to a more compact and hydrophobic micellar structure. Moreover, for the C12C3C12Br2/TX100 mixed micelle containing C12C3C12Br2 with a shorter spacer, the more pronounced decrease of N(T) at X(TX100) lower than 0.8 may be attributed to the larger steric repulsion between headgroups of TX100. Meanwhile, the increase of microviscosity and the decrease of micropolarity are more marked for the C12C12C12Br2/TX100 mixed micelle, owing to the looped conformation of the longer spacer of C12C12C12Br2.     

C12-s-C12•2Br和己醇混合水溶液的胶团化行为

己醇的加入使C12-s-C12•2Br（s=3,4,6）的临界胶团浓度cmc降低,s越大其影响也越显著.己醇参与组成了混合胶团,当添加的己醇量相同时,它在混合胶团中的摩尔分数几乎一样.混合胶团表面反离子解离度随己醇浓度增大而增大.     

Organic reactions in chiral micelles: 7. The structural effects on the asymmetric oxidation of prochiral sulfides in chiral micelles

A variety of phenyl alkyl sulfides were oxidized enantioselectively with NaIO₄ in chiral micellar systems formed from eight chiral surfactants, to give optical active sulfoxides. The enantiomer excesses ranged from 1.6 to 15.0%. To understand the mechanistic detail of this asymmetric oxidation in chiral micelle, the effects of structure both in substrates and surfactants on the optical yield of the oxidation were studied and discussed. Generally, increasing the alkyl chain length both in surfactants and in substrates enhances the optical yield, also the surfactant with hydroxy group at its appropriate position gives better enantioselectivity, suggesting the enzymic characteristics of the chiral micelle.