Mixed micelles of some metal dodecyl sulfates and triton X-100 in aqueous media

Tensiometric studies on several binary surfactant mixtures containing anionic surfactants, viz., metal (lithium, sodium, potassium, copper, cobalt, and magnesium) dodecyl sulfates and a nonionic surfactant (Triton X-100) in water at different mole fractions (0–1) provide critical micelle concentration (CMC) values. The composition of mixed micelles and the interaction parameter, β, evaluated from the CMC data for different systems using Rubingh's theory, are discussed. Marked interaction is observed with monovalent dodecyl sulfates. The influence of counter-ion valence on the formation of mixed micelles was investigated for anionic-nonionic systems, and results indicated that mixed systems with bivalent counter-ions in metal dodecyl sulfate resembled nonionic-nonionic systems where weak/negligible interaction has been reported. Salt addition revealed the weakening of interaction in the mixed systems, which is attributed to the head group charge neutralization and the dehydration of the ethylene oxide units of the nonionic surfactants. A few cloud point and viscosity data are also reported.     

Mixed micelles of cationic surfactants and bile acid salts in aqueous media

Critical micelle concentrations of cetyltrimethylammonium-p-toluene sulfonate (CTAT) and cetylpyridinium chloride (CPC) with sodium cholate (NaC) and sodium deoxycholate (NaDC) were determined in aqueous solutions by surface tension measurements. Interaction parameters and mole fraction of the components in mixed micelles were estimated using Rubingh's theory. Strong interaction was observed for each mixed system, a common feature shown by anionic-cationic mixtures. Dramatic effects on the viscosities of these cationic surfactant-bile salt mixtures were seen, and were markedly dependent upon the counterion of the cationic surfactant and the nature of bile salts. Micelles are small and spherical for cationic surfactants in the presence of NaC. Micelle growth was seen for CPC in the presence of NaDC by an increase in viscosity, but a CTAT solution showed an opposite effect on addition of NaDC. Conductance results supported this view. Different behavior of the two bile salts is explained on the basis of their orientation in cationic micelles.     

Mixed micelles of hexadecylpyridinium bromide + tetradecyltrimethylammonium bromide in aqueous glycol oligomers

Conductances of hexadecylpyridinium bromide (HPyBr) + tetradecyltrimethylammonium bromide (TTAB) mixtures over the entire mole fraction range of HPyBr (α_HPyBr) were measured in pure water as well as in the presence of various aqueous ethylene glycol oligomers containing 10 and 30 wt% of each additive in their respective binary mixtures at 30°C. Each conductivity curve shows two breaks corresponding to two critical micelle concentrations (cmc; C₁ and C₂ over the whole mole fraction range of HPyBr + TTAB mixtures except in the presence of pure HPyBr and TTAB, where a single break was observed. From the conductivity data, various micellar paramelers in the absence and presence of glycol additives were computed. A variation in the micellar parameters in the presence of additive showed that additive introduction mainly influence the medium properties and therefore the micellar properties. However, no significant micelle-glycol interactions were observed even with an increase in the number of repeating units from ethylene glycol to polyethylene glycol 600. The mixing behavior of HPyBr + TTAB is close to nonideal and is identical in pure water and in the presence of various glycols. This has been attributed to the presence of synergistic interactions between unlike monomers at C₁ that are not influenced even by the presence of additives. The appearance of the second cmc is mainly attributed to structural transitions of the mixed micelles at C₁ with a further increase in surfactant concentration.     

Hydrophobic hydration of cationic mixed micelles by alkoxyethanols in aqueous media

The conductances of hexadecylpyridinium chloride (HPyCl) + tetradecyltrimethylammonium bromide (TTAB) mixtures over the entire mole fraction range of HPyCl (α_HPyCl) were measured in aqueous binary mixtures of ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and diethylene glycol monobutyl ether containing 10 to 30 wt% additive in their respective binary mixtures at 30°C. Each conductivity curve showed a single break over the whole mole fraction range of HPyCl + TTAB mixtures. From the break in the conductivity curve, various micellar parameters were calculated and the results were discussed on the basis of alkoxyethanol's hydrophobic hydration of the mixed micelle. The micellar parameters of HPyCl, TTAB, and of their mixtures showed a strong dependence both on the amount and on the number of repeating units of ethylene and diethylene glycol derivatives. The hydrophobic hydration was considerably higher in the case of diethylene glycol derivatives owing to the presence of an extra ether oxygen. An evaluation of the non-ideality in the HPyCl + TTAB mixtures in the presence of additives revealed that alkoxyethanols reduce the unlike surfactant monomer interactions in order to form the mixed micelles in comparison to those in pure water. It has also been observed that such interactions systematically decrease with an increase in the number of repeating units from monomethyl ether to monobutyl ether, both in the case of ethylene and diethylene glycol derivatives.     

Surfactant-polymer interactions: Mixed micelles of hexadecylpyridinium bromide and trimethyltetradecylammonium bromide in aqueous poly(vinylpyrrolidone) solution

The conductance of hexadecylpyridinium bromide (HPyBr) and trimethyltetradecylammonium bromide (TTAB) mixtures over the entire mole fraction range of HPyBr (α_HPyBr) was measured in aqueous poly(vinylpyrrolidone) (PVP) solution containing 1, 5, and 10 wt% PVP at 30°C. Each conductivity curve showed two breaks corresponding to two aggregations throughout the whole mole fraction range of HPyBr and TTAB mixtures except for pure TTAB for which a single break corresponding to the conventional critical micelle concentration was observed. The two aggregation processes in the presence of low amounts of PVP were mostly similar to those in pure water, however, 10 wt% PVP shifted the break, corresponding to the second aggregation, toward the higher value. This was attributed to HPyBr/PVP interactions, which were also evident from the appearance of a second break in the conductivity (κ) plot of pure HPyBr in aqueous 10 wt% PVP. From conductivity data, various micellar parameters in the presence of PVP were determined and discussed from the standpoint of micelle-polymer interactions. The mixing behavior of HPyBr and TTAB corresponding to the first break in the presence of PVP was ideal for the most part and identical to that in pure water.     

Solubilization of octafluoronaphthalene by mixed micelles of fluorocarbon and hydrocarbon surfactants in aqueous solutions

Solubilization of octafluoronaphthalene (OFN) by fluorocarbon and hydrocarbon surfactants in aqueous solutions has been examined to investigate the effects of mixing surfactants and added salt. Diethylammonium perfluoronanoate (DEAPFN) micelles have the most solubilization power toward OFN. The difference in micellar solubilization power will be caused by the hydrophobicity of ionic groups and micellar size. Large positive synergistic effects on solubilization behavior were observed in the DEAPFN-diethylammonium tetradecyl sulfate mixed micellar systems. Solubilization of OFN depended on the concentrations of added salt and the aggregation number, that is, the micellar size.     

Solubilization of phospholipid vesicular structures into mixed micelles of zwitterionic surfactants

Interactions between the binary combination of dimethyltetradecylammoniopropanesulfonate (TPS) and l-α-phosphatidylcholine (PC), 1,2-didecanoyl-sn-glycero-3-phosphocholine, and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine in the aqueous bulk phase were evaluated with the help of pyrene fluorescence (l ₁/l ₃) measurements by studying the aggregation processes of TPS in pure water and in the presence of 7–36 μM of fixed concentrations of each lipid. The fluorescence measurements showed that TPS monomers undergo two kinds of aggregation process, which were identified by the three breaks. The first break, C₁, and the second, C₂, indicated the onset and completion of bilayer solubilization, respectively, on the incorporation of TPS monomers into the bilayer assemblies, which led to bilayer solubilization in the form of mixed micelles. This process was not clearly visible in the presence of PC, whereas some kinds of structure transitions were observed upon the incorporation of surfactant monomers. The partition coefficient (K), which defines the degree of partitioning of surfactant monomers into the bilayers with respect to the aqueous medium, was evaluated. A high K value of TPS-lipid aggregates indicated stronger interactions between surfactant and bilayer assemblies of lipid. The K values determined for the three phospholipids are close to each other, which indicates that K values do not depend on the hydrocarbon chain length of the phospholipid but of the surfactant used.     

Temperature and salt-induced micellization of some block copolymers in aqueous solution

Micellization of three commercial samples of ethylene oxide (EO)-propylene oxide (PO) (PEO-PPO-PEO) triblock copolymers (pluronics) P65 (EO₂₅PO₃₀EO₂₅, mw PPO=1750, %PEO=50), P85 (EO₂₅PO₄₀EO₂₅, mw PPO=2250, %PEO=50), and F88 (EO₁₀₂PO₄₀EO₁₀₂, mw PPO=2250, %PEO=80) in aqueous sodium chloride solution (0–3 M) was examined by cloud point, surface tension, dye spectral change, fluorescence, and viscosity measurements over a temperature range of 25–50°C. Salt-induced micellization and micelle growth were observed. The presence of sodium chloride enhanced hydrophobicity in the PPO moiety and reduced hydrophilicity of PEO moieties, favoring micellization at relatively lower concentrations than in water at ambient temperature. The effect of salt on micellization is similar to that of increasing temperature. The critical micelle concentrations (CMC) and critical micelle temperatures showed a marked decrease in the presence of added salt. CMC obtained by different methods were in good agreement.     

Synergistic solubilization of decafluorobiphenyl by micelles of fluorocarbon surfactants

Solubilization of decafluorobiphenyl (FBIP) by surfactants in aqueous solution was examined to investigate the properties of micelles composed of surfactants having a per-fluorocarbon chain. Fluorocarbon surfactants solubilize FBIP better than hydrocarbon surfactants. Significant solubilization by fluorocarbon surfactants was observed upon addition of salt. Highly synergistic solubilization of FBIP using surfactant mixtures was also observed for fluorocarbon and hydrocarbon surfactants in the presence of salt. The high solubilization ability of surfactants can be attributed to micelle growth. A simple geometrical consideration of molecular packing in micelles revealed that the characteristic micelle is composed of bulky fluorocarbon chains. The solubilization behavior accompanied by micelle growth would be closely associated with a change in interfacial contact area between the micelle core and bulk water. The behavior of fluorescence intensity of micelle-solubilized FBIP also indicated a change in micropolarity of fluorocarbon micelles accompanied by micelle growth.     

Interaction between bisphenol A and micelles of ionic surfactants

Interactions between bisphenol A (BPA) and ionic surfactants—cationic hexadecyltrimethylammonium bromide (HTAB) and anionic sodium dodecylsulfate (SDS)—were studied by measuring interfacial tensions and the intensities of pyrene fluorescence. The critical micellar concentrations (CMC) decreased with an increase in the BPA concentration, and the degree of that decrease was greater in HTAB than in SDS. In those micelles, BPA interacted more strongly with HTAB than with SDS. Conversely, BPA adsorbed on the air-water interface cooperatively with the surfactants, even though almost no adsorption of BPA itself was observed. This cooperative adsorption was more enhanced with HTAB than with SDS. Thus, BPA worked on the surfactants to stabilize the micelles and interfacial adsorption. The stability gained by the addition of BPA was greater on the interface than in the micelle. This was evidence of decreased hydrophilicity of the head group of the ionic surfactant, which interacted with BPA, because this decrease acted on the surface activities of the surfactants more directly than on the micelle stabilities. Pyrene fluorescence measurements yielded identical results for the effect on micelle stabilities. It is noteworthy that the fluorescence intensity of peak 1, l ₁, decreased with an increase in BPA concentrations at constant concentrations of surfactant greater than the CMC, but the peak ratio, l ₁/l ₃, remained almost unchanged. This fact was also related to the interaction of BPA with the hydrophilic head groups in the surfactant micelle.     

Synergism in mixed monolayers of alkylpolyglucoside and alkylsorbitan surfactants at liquid/liquid interface

A study of nonideal behavior in the formation of mixed monolayers at the oil-water interface was performed for a nonionic-nonionic surfactant system. Mixtures containing alkylpolyglucoside and alkylsorbitan derivatives were investigated. As the oily phase, colza-rapeseed and olive oils were used. To evidence a synergetic effect in the interfacial tension reduction in the oil-water-surfactant-cosurfactant system, the model based on the regular solution theory was modified for the case of both surfactants being soluble in the water as well as in the oily phase. For determination of the condition for the synergism and the point of the maximum synergetic effect, the molar fraction in the mixed monolayer X ^s and the interaction parameter β^s were calculated, using experimental data for the interfacial tension and for the partition coefficient. A set of general equations was developed, to allow the analysis of a mixture containing a water-soluble and an oil-soluble surfactant. The equations are applied according the characteristics of studied quaternary systems. The mathematical model was tested with literature data, and the results were compared with those obtained from the phase diagram of oil-water-mixed surfactant system. The systems water-vegetable oil-alkylpolyglucoside-alkylsorbitan show a maximum synergetic effect at molar fractions between 0.85 and 0.90. The liquid-liquid interfacial tension and partition coefficient data were used to calculate the point of the maximum synergetic effect, i.e., the surfactant-cosurfactant ratio, which ensures the interfacial tension miniumum. The dramatic reduction in interfacial tension due to the presence of the surfactant mixture at the interface at the point of the synergism maximum is related to the formation of three-phase and single-phase microemulsions. The results were applied to obtain single-phase microemulsion in water-vegetable oil-alkylpolyglucoside-alkylsorbitan systems.     

Effect of temperature and pH values on aggregation behavior of polymeric surfactants in aqueous solution

A novel kind of polymeric surfactant based on carboxymethyl cellulose and poly(ethylene oxide) dodecyl ether acrylate (CMC‐AR₁₂EO₉) was synthesized through ultrasonic irradiation. Aggregation behavior in aqueous solution at different temperatures and pH values was investigated by dynamic laser scattering and fluorescence probe. The results show that, with the increase of temperature, polymeric surfactants are favorable to form multimolecular micelles with narrower polydispersity of size distribution. At a higher temperature, the multimolecular micelles tend to aggregate bigger sized particles that are unstable and would be disaggregated at higher shear rate. At the elevated pH values, the size of micelles reduces drastically because of strong damage of alkali to aggregates, whereas nonpolar and insoluble domains formed by the hydrophobic blocks of polymeric surfactants are insensitive to pH changes. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 945–949, 2005     

Gemini表面活性剂复配体系研究进展

Gemini表面活性剂的特殊结构使其具有独特的优越性能,在不同的表面活性剂复配体系中表现了潜在的应用价值。文章简要介绍了Gemini表面活性剂的结构与性质,综述了近几年各类Gemini表面活性剂复配体系的发展现状,发现Gemini表面活性剂的存在可使复配体系有更强的协同作用。最后概括了表面活性剂复配体系的应用并对表面活性剂复配体系的发展趋势做了展望。     

Kao系列桶混助剂的增效作用及其增效机制

室内外试验结果证明,桶混助剂KAOADJUVANTA-134和KAOADJUVANTA-145分别对不同除草剂和杀虫剂具有显著的增效作用,平均可以减少农药使用量三分之一以上。同时,使用助剂后可显著提高耐雨水冲刷的能力。比较添加助剂前后各药剂润湿性能和渗透性能,发现添加这类桶混助剂能显著降低药剂的表面张力和界面张力,使药剂在叶面的铺展性和润湿性更好。添加助剂后,药剂在植物角质膜和气孔渗透方面的性能均显著增加。同时提高润湿性和渗透性是该系列助剂具有显著增效作用的主要原因。     

Copolymerization of aniline and styrene using various surfactants in aqueous media

Polyaniline/polystyrene (PAn/PS) copolymer was prepared in the aqueous solution by copolymerization of styrene and aniline using potassium iodate (KIO₃) and ammonium persulfate ((NH₄)₂S₂O₈) as an oxidant in the presence of various surfactants such as poly(ethylene glycol), hydroxypropylcellulose, and surfactive dopant sodium dodecylbenzenesulfonate. The PAn/PS copolymer was characterized in terms of conductivity, morphology, chemical structure, and glass transition temperature. The results indicate that the morphology, conductivity, and glass transition temperature of products are dependent on the type of surfactant. Furthermore, it was found that addition of styrene monomer into stirred aqueous solution influences the surface morphology. The chemical structure and glass transition temperature of product were studied by Fourier transform infrared spectroscopy and differential scanning calorimetry respectively. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

A study of the versatile micropatterns of diblock copolymer micelles: the effect of copolymer concentration, substrate, film thickness and micelles morphology

We report the novel use of polystyrene-block-poly(acrylic acid) (PS-b-PAA) diblock copolymer micelles as the nano-building blocks in fabricating orderly aligned three-dimensional micropatterns with high regularity through a one-step evaporation-induced cracking process. Crack patterns of square, rectangular, stripe-like and mesh-like structures in micron scale were obtained. The effect of the concentration of diblock copolymer, the properties of the substrates, the thickness of the drying layer, and the morphology of the micelles on the regularity of the crack patterns was studied. By regulating the above factors, we achieved micropatterns of various structures. We further developed a cheap, fast, and simple method for fabricating micromolded structures using the crack patterns as templates.     

双亲性无规共聚物自组装胶束化研究

以偶氮二异丁腈(AIBN)为引发剂，由大分子单体己内酯改性丙烯酸酯(FA)、甲基丙烯酸甲酯(MMA)和亲水性单体丙烯酸(AA)在N，N-二甲基甲酰胺(DMF)中通过自由基共聚反应得到双亲性类接枝共聚物(MAF)。将MAF与可生物降解均聚物聚己内酯(PCL)在水溶液中进行自组装，形成以。MAF中PFA链段与PCL为核、MAF中PAA链段为壳的核壳结构复合纳米胶束，进一步对PAA壳进行化学交联，最终得到具有核壳结构的复合纳米微球。动态激光光散射(DLS)和透射电子显微镜(TEM)结果显示胶束为球形，粒径在100nm左右且呈窄分布，有一定的核壳结构。     

Kinetics and stability of a chromobacterium viscosum lipase in reversed micellar and aqueous media

The lipolytic activity of Chromobacterium viscosum lipase B (EC 3.1.1.3.; triacylglycerol hydrolase) solubilized both in water and AOT/isooctane reversed micelles has been investigated using triolein as a substrate. The influence of relevant parameters in the catalytic activity such as temperature, pH, surfactant and substrate concentrations, and water content was tested and compared in both media. A study of stability of the lipase was carried out, with particular reference to the influence of pH. Three major effects of the encapsulation of the lipase in the micelles were observed: increased activity (up to 7 times higher than in water), greater stability, specially at pH 7, and higher resistance to thermal deactivation.     

Micellization behavior of ionic liquid surfactants with two hydrophobic tail chains in aqueous solution

The drop volume method was used to determine the surface tensions of two series of polymerizable ionic liquid surfactants, namely, 1‐acryloyloxypropyl‐3‐alkylimidazolium chloride [APC_nim][Cl] (n = 8, 10, 12) containing two hydrophobic tail chains and 1‐propionyloxypropyl‐3‐alkylimidazolium chloride [PPC_nim][Cl] (n = 8, 10, 12), which showed similar structures with [APC_nim][Cl] (n = 8, 10, 12) at 25°C. The surface properties of the surfactants were also compared. Furthermore, the thermodynamic behavior of [PPC_nim][Cl] (n = 10, 12, 14) micellization in aqueous solution and the enthalpy–entropy compensation phenomenon were studied. The two kinds of surfactants had high surface activity. Double bonds had almost no effect on the surface properties of [APC_nim][Cl]. The micellization of [PPC_nim][Cl] in aqueous solution was spontaneous and entropy‐driven. For the surfactant with specific structure, micellization ability initially increased and then decreased with temperature increase. The entropic contribution to Gibbs free energy change tended to decrease, whereas the enthalpic contribution increased. In addition, the enthalpy–entropy compensation phenomenon occurred during the micellization process. For all [PPC_nim][Cl], the compensation temperature was (314 ± 1) K, which remained unaffected by the surfactant molecular structure. However, when the hydrophobic carbon chain length increased, both micelle formation ability and stability increased. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Cloud point phenomena in mixtures of anionic and cationic surfactants in aqueous solution

The interaction between anionic and cationic surfactants was investigated by means of surface tension, conductivity, and nuclear magnetic resonance. It was found that a strong interaction exists between anionic and cationic surfactants and the mixed surfactant has a hydrophobic property. The phase diagram has been determined as a function of temperature for the waterstearyltrimethylammonium chloride (STAC)-sodium laurate (NaL). The Krafft point rose remarkably in equimolar mixtures for this system. The phase diagram has been determined as a function of temperature for the STAC-sodium-N-lauroyl-N-methyl-β-alanine (NaLMA) system. The liquid-liquid phase separation phenomenon was observed around an equimolar mixture. It can be identified with the cloud point, which is shown by nonionic surfactants. This phenomenon seemed to be caused by the decreased solute-solvent interaction (i.e., dehydration of the amido group contained in NaLMA molecule) as the temperature is raised. The decreasing effect of protein (ovalbumin) denaturation was observed in the high area of the mole fraction of cationic surfactant in the cationic-anionic system. We believe that this is due to the remarkable lowering of the monomer concentration by the formation of a hydrophobic complex.