用石英晶体微天平研究表面活性剂在银固态表面上的动态吸附

吸附是表面活性剂的一个重要特征.迄今用于原位监测表面活性剂在固体表面上吸附重量变化的方法尚不多见.近年来压电石英晶体作为一种高灵敏的质量传感器(石英晶体微天平)已被用于大气和溶液中多种微量成分的监测.用石英晶体微天平研究I~-、Br~-和表面活性剂在金电极上的吸附行为亦有报道.本文研究了十六烷基三甲基溴化铵(CTAB)、十二烷基磺酸钠(SDSO)、十二烷基硫酸钠(SDS)在银固态表面上的吸附平衡动力学特性及其吸附机制.     

Effects of surfactants on the photosensitized production of tyrosine radicals studied by photo-CIDNP

The influence of the surfactants sodium dodecyl sulphate, cetyltrimethyl-ammonium bromide and triton X-100 on the photochemically induced dynamic nuclear polarization (CIDNP) of N-acetyl tyrosine has been investigated. Three photosensitizers were used to generate polarization: thionin, eosin Y and flavin mononucleotide. 600 MHz 1H photo-CIDNP experiments, supported by laser flash photolysis transient absorption measurements, indicate that the neutral triton surfactant has no influence on the nuclear polarization, but that the other two, charged, amphiphiles affect the photochemistry in a variety of ways, depending on the surfactant concentration and the identity of the sensitizer.     

Self-organization of double-chained and pseudodouble-chained surfactants: counterion and geometry effects

Self-organization in aqueous systems based on ionic surfactants, and their mixtures, can be broadly understood by a balance between the packing properties of the surfactants and double-layer electrostatic interactions. While the equilibrium properties of micellar systems have been extensively studied and are understood, those of bilayer systems are less well characterized. Double-chained and pseudodouble-chained (or catanionic) surfactants are among the amphiphiles which typically form bilayer structures, such as lamellar liquid–crystalline phases and vesicles. In the past 10–15 years, an experimental effort has been made to get deeper insight into their aggregation patterns. With the double-chained amphiphiles, by changing counterion, adding salt or adding anionic surfactant, there are possibilities to depart from the bilayer aggregate in a controlled manner. This is demonstrated by several studies on the didodecyldimethylammonium bromide surfactant. Mixtures of cationic and anionic surfactants yield the catanionics, surfactants of the swelling type, and also show a rich phase behavior per se. A variety of liquid–crystalline phases and, in dilute regimes, equilibrium vesicles and different micellar shapes are often encountered. Phase diagrams and detailed structural studies, based on several techniques (NMR, microscopy and scattering methods), have been reported, as well as theoretical studies. The main features and conclusions emerging from such investigations are presented.     

Phase Behavior of Bis(Quaternary Ammonium Bromide)/Sodium Cholate/H2O System

Interactions in an oppositely charged surfactant mixture composed of a gemini surfactant (bis(quaternary ammonium bromide)) and a bile salt (sodium cholate) in water were studied at 30°C. A combination of techniques was used including surface tension, conductometry, light scattering, light microscopy, and microelectrophoretic measurements. A strong dependence of the phase behavior on the molar ratio and actual concentration of surfactants was found. The interplay between electrostatic effects, geometry of molecules, and dissimilar separation of the hydrophobic and hydrophilic moieties in the surfactants dictate the interaction mode and the microstructures formed. Instead of precipitation, in the equivalent mixtures formation of complexes, mixed micelles, vesicles, coacervates, and solid crystalline phases have been observed. The extent of interacting forces in mixed micelles formed in equivalent mixtures was evaluated by regular solution theory. A relatively high negative value of interaction parameter indicated a strong attractive interaction between surfactants. The compositions of both mixed micelles and mixed monolayer are found to be almost equimolar.     

Catanionic aggregates formed from drugs and lauric or capric acids enable prolonged release from gels

The aim of this study was to add to the range of charged surfactants that can be used to form catanionic aggregates with oppositely charged surface active drug substances; and to apply these aggregates to prolong drug release from gels. The surfactants used in this study, lauric and capric acids are of natural origin-unlike traditionally used, synthetic, surfactants. The mixtures of drug substances and oppositely charged surfactants were studied visually and with cryogenic transmission electron microscopy. Drug release from gels was studied with a modified USP paddle method. This study shows that lauric and capric acids are as, or even more, active in forming catanionic aggregates than traditionally used surfactants such as sodium dodecyl sulfate. It is shown that the length of the hydrophobic part of the surfactant plays an important role in the formation of pharmaceutically interesting catanionic aggregates. As seen in previous studies, using catanionic vesicles prolongs the drug release from gels and decreases the apparent diffusion coefficient by a factor of 10-50, compared to a gel containing only drug substance.     

聚氧乙烯与非等摩尔正负离子表面活性剂混合体系的相互作用

通过黏度、动态光散射和透射电镜方法研究了聚氧乙烯(PEO)对正负离子混合表面活性剂癸基磺酸钠(C₁₀SO₃)-癸基三乙基溴化铵(C₁₀NE)聚集体的影响. 实验结果表明, 加入PEO后, 非等摩尔C₁₀SO₃-C₁₀NE混合物的聚集体大小没有明显改变, 只有等摩尔混合物的聚集体发生了明显的长大, 且仍为囊泡, 说明PEO只对囊泡体系有显著的影响, 对胶团体系则没有明显的影响. 在接近等摩尔混合时, 混合体系中C₁₀SO₃与C₁₀NE过量程度相同的情况下, PEO对C₁₀NE过量的体系影响更大. PEO对囊泡体系的影响主要表现为PEO通过对囊泡的“空缺絮凝”作用(Depletion interaction)使囊泡长大, 而对于非等摩尔混合的胶团溶液, 由于胶团之间存在较强的静电排斥作用而无法发生聚集. PEO对C₁₀NE过量的体系影响更大, 主要是由于C10NE过量体系中的聚集体比C10SO3过量体系中的更接近于等摩尔组成.     

Characterization and Aggregation Behaviors of Mixed DDAB/SDS Solution With and Without Poly(4-styrenesulfonic Acid-Co-Maleic Acid) Sodium

Synthetic vesicles are formed by cationic and anionic surfactants, didodecyldimethylammonium bromide (DDAB), and sodium dodecylsulfate (SDS). The morphology, size, and aqueous properties of cationic/anionic mixtures are investigated at various molar ratios between cationic and anionic surfactants. The charged vesicular dispersions made of DDAB/SDS are contacted or mixed with negatively charged polyelectrolyte, poly(4-styrenesulfonic acid-co-maleic acid) sodium (PSSAMA), to form complexes. Depending on DDAB/SDS molar ratio or PSSAMA/vesicle charge ratio, complexes flocculation or precipitation occur. Characterization of the cationic/anionic vesicles or complexes formed by the catanionic vesicles and polyelectrolytes is performed by transmission electron microscope (TEM), dynamic light scattering (DLS), conductivity, turbidity, and zeta potential measurements. The size, stability, and the surface charge on the mixed cationic/anionic vesicles or complexes are determined.     

正负离子表面活性剂与高聚物混合双水相体系的相行为及蛋白质的分配

报道了由正负离子表面活性剂与高聚物混合溶液形成的一种可用于蛋白质的分离及分析的新型双水相萃取体系.研究了正负离子表面活性剂(溴化十二烷基三乙铵/十二烷基硫酸钠)分别与葡聚糖和聚乙二醇混合双水相体系的形成规律、相行为及牛血清蛋白和溶菌酶在双水相体系中的分配.通过在高聚物分子中接上亲和配基,研究蛋白质在双水相体系中的亲和分配.结果表明,在该体系中,表面活性剂与高聚物分别富集于不同相中.升高温度及加入无机盐均可促进双水相体系的形成,不同蛋白质可分配于不同的相中.亲和配基的引入极大地增强了蛋白质分配的选择性.     

Lamellar phase formation in catanionic mixtures of hydrogenated and fluorinated surfactants: a comparative study

The properties and phase behaviors of the catanionic mixtures consisting of tetradecyltrimetylammonium bromide (TTABr) and different anionic surfactants (i.e., sodium docanoate, C₁₀HOONa; sodium laurate, C₁₂HOONa; sodium perfluorodecanoate, C₁₀FOONa) were examined, in particular when the molar mixing ratio in the aqueous solution was exactly 1:1. Although the three inspected systems have identical head groups and counterions, they exhibited very different lamellar (L_α) phases. When using the hydrogenated surfactants, the C₁₀HOONa–TTABr system formed domain-like L_α/L₁ two phases and the C₁₂HOONa–TTABr system formed cream-like L_α/L₁ two phases, respectively. In the case of the perfluorinated surfactant, the C₁₀FOONa–TTABr system formed interdigitated and tilted L_α gel. The microstructures of the three L_α phases were characterized by polarized microscope, freeze-fracture transmission electron microscope, small angle X-ray scattering, and X-ray diffraction. The phase transition of the lamellar gel at different temperature was studied by differential scanning calorimetry and rheological measurements. The results elucidated the formation of the L_α phase in catanionic mixtures containing hydrogenated or fluorinated anionic surfactants with molar mixing ratio of 1:1.     

The effect of crystallization behavior on high conductivity,enhanced mechanism and thermal stability of poly(ε-caprolactone)/multi-walled carbon nanotube composites

Poly(ε-caprolactone) (PCL) composites filled by multi-walled carbon nanotubes (MWCNTs) which was non-covalently modified by the combined surfactants of poly(sodium 4-styrenesulfonate) and cetyltrimethyl-ammonium bromide (PSS-CTAB) were fabricated via simple solution precipitation method. PCL/MWCNTs composites provided with the low procolation threshold (0.4?wt%) and high electrical conductivity due to good dispersion of MWCNTs. And the excellent mechanical properties and enhanced thermal stability were also obtained with the addition of modified MWCNTs. In addition, all PCL composites showed significantly enhanced crystallization with increasing the MWCNTs contents, which demonstrated that the MWCNT-induced crystallization of PCL could effectively regulate the properties of composites. In a word, introducing non-covalent functionalized MWCNTs in the polymer system was a promising way for developing excellent conductive composites.     

Effect of self‐assemblies of various surfactants in their single and mixed states on the BZ oscillatory reaction

Micelles of different surfactants are well known to affect chemical equilibria and reactivities by selectively sequestering the reagent substrates through electrostatic and hydrophobic interactions. In this article, the effects of micelles of various surfactants on different parameters of the Ce(IV)‐catalyzed Belousov–Zhabotinsky (BZ) oscillatory reaction at 35°C in nonstirred closed conditions are studied by employing spectrophotometry and tensiometry. Surfactants used in this study are the cationics hexadecyltrimethylammonium bromide (CTAB) and pentamethylene‐1,5‐bis(N‐hexadecyl‐N,N‐dimethylammonium)bromide gemini (Gemini), anionic sodium dodecylbenzene sulfonate (SDBS), and nonionic Brij58, whereas the binary surfactant systems used are cationic–nonionic CTAB+Brij58 and anionic–nonionic SDBS+Brij58. The results revealed that the induction period shows a definite variation with increasing concentration of different surfactants above their critical micelle concentration (cmc). The amplitudes of oscillation and absorbance maxima and minima are enhanced in the presence of micelles of CTAB and Gemini surfactants, whereas micelles of SDBS and Brij58 have almost no effect on the nature of the oscillations. However, mixed micelles of CTAB+Brij58 and SDBS+Brij58 binary mixtures show a quite different effect on the overall behavior of the oscillations. The enhanced effect of CTAB and Gemini surfactants on the overall nature of oscillations has been attributed to the positive charge on the surface of their micelles and to some extent on the presence of nitrogen in their head group. The effect of mixed binary micelles may be attributed to their synergistic nature. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 659–668, 2010     

N-烷基-N-(2-羟乙基)-N,N-二甲基溴化铵与十二烷基硫酸钠复配系统的双水相

合成了N-十二烷基-N-(2-羟乙基)-N,N-二甲基溴化铵、N-十四烷基-N-(2-羟乙基)-N,N-二甲基溴化铵和N-十六烷基-N-(2-羟乙基)-N,N-二甲基溴化铵等3个季铵盐阳离子表面活性剂. 研究了它们以及N-十六烷基-N,N,N-三甲基溴化铵(CTAB)与阴离子表面活性剂十二烷基硫酸钠(SDS)复配系统在313.15 K时的双水相行为. 复配系统在两个非常狭窄的区域能形成双水相, 两相区近似以等摩尔线为中心对称分布, 随着阳离子表面活性剂碳链长度的增长, 富含阳离子表面活性剂的双水相区向阴阳离子表面活性剂摩尔比减小的方向稍有移动.     

Solute-solvent interactions in micellar electrokinetic chromatography: IV. Characterization of electroosmotic flow and micellar markers

A wide study of the compounds and procedures mostly used to determine the electroosmotic flow (EOF) and micelle elution times has been done in seven different micellar electrokinetic chromatography (MEKC) systems. These systems are formed from mixtures of an aqueous buffer with the surfactants sodium dodecyl sulfate, lithium dodecyl sulfate, lithium perfluorooctane sulfonate, sodium cholate, sodium deoxycholate, tetradecyltrimethylammonium bromide and hexadecyltrimethylammonium bromide. The solvation parameter model has been used to evaluate the usefulness of the compounds studied as EOF or micellar markers in each of the seven MEKC systems. It is demonstrated that methanol, acetonitrile and formamide are the best EOF markers, and that dodecanophenone is the best micellar marker.     

表面活性剂双水相界面性质的研究

表面活性剂双水相是指正、负离子表面活性剂混合水溶液在一定浓度及混合比 范围内，自发分离形成的两个互不相溶的水相。前文报道了将其作为一种新型萃取 体系，用于生物活性物质的分离。目前有关其相行为、化学物质和生物大分子的分 配方面已有较多研究，但未见两相之间界面化学性质研究的报道。表面活性剂双水 相的形成是一种奇特的相分离现象，两个稀水溶液（含水量可高达99%以上）互不 相溶、平衡共存，其界面结构和界面张力必有其特殊性。     

Adsorption, association and precipitation in hexadecyltrimethylammonium bromide/sodium dodecyl sulfate mixtures

The phase equilibria of surfactant aqueous mixtures, hexadecyltrimethylammonium bromide and sodium dodecyl sulfate, have been studied by polarizing microscopy, quasielastic light scattering, conductivity, potentiometric, electrophoretic, and surface tension measurements. Adsorption at the air/solution interface, association and precipitation in bulk solution strongly depended on the molar ratio and the concentration of surfactants. Catanionic vesicles coexisted with crystalline catanionic salts in a broad concentration range. The relative proportions of crystallites and vesicles varied according to the concentration and the molar ratio of the surfactants. The solid crystalline phase was progressively converted to catanionic vesicles with increasing surfactant molar ratio. At the highest excess of one of the surfactants transition from catanionic vesicles to mixed micelles occurred. The formation and stability of different phases are discussed in terms of surfactant molecular packing constraints and electrostatic interactions in the headgroup region. Surfactant tail-length asymmetry and the change of electrostatic interactions in the headgroup region from attractive to repulsive are governing factors for the transition from planar to curved bilayers. Received: 9 June 1998 Accepted: 18 August 1998     

UV causes dramatic changes in aggregation with mixtures of photoactive and inert surfactants

Aqueous mixtures of photosensitive and inert surfactants have been prepared; photoreactions and changes in aggregation after irradiation have been characterized. The photosensitive component was a stilbene-containing gemini photosurfactant (E-SGP), and the inert surfactants were either DTAB (dodecyltrimethylammonium bromide) or one of two different gemini surfactants, 12-4-12 or 16-4-16 (butanediyl-1,4-bis(dodecyldimethylammonium bromide) or butanediyl-1,4-bis(hexadecyldimethylammonium bromide)). Small-angle neutron scattering (SANS) studies revealed that in general the initial nonirradiated mixed systems form vesicle-type aggregates (100-200 angstroms radius), in equilibrium with some smaller charged spheroidal or ellipsoidal micelles (approximately 20 angstroms radius). In all cases, UV irradiation resulted in disruption of these vesicles and the formation of charged micelles. 1H NMR showed that the main photoproduct is the cis, anti, cis dimer of E-SGP (ZEZ-DiSGP); hence, photochemically induced changes in the reactive SGP drive significant changes in the preferred aggregation structure. These results demonstrate the utility of photoactive surfactants in mixtures with inert analogues.     

Interactions in solution between a hydrophobic polymer and various kinds of surfactants

Interactions in solution between a hydrophobic polymer and surfactants were studied by viscometry, light scattering and conductimetry measurements. One polymer, poly(2-ethyl hexyl methacrylate) (P2EHMA), five surfactants, sodium dodecyl sulfate (SDS), hexadecyl trimethylammonium bromide (HTAB), hexadecyl pyridinium chloride (HPCl), and ethoxylated nonyl phenol containing 10 or 25 segments of ethylene oxide (NP10 or NP25), and one solvent mixture, THF/6 vol% H₂O were used in this work. For the P2EHMA/surfactant mixtures in THF/6 vol% H₂O, the viscosity versus surfactant concentration curves are similar in shape for all surfactants. They show a minimum at low surfactant concentration followed at higher concentration by a maximum and a plateau. An interpretation of these curve shapes is proposed. The relevance of these findings to the problem of the polymer/surfactant interactions in latexes and latex films is also discussed.     

Peculiarities of the Porous Structure of Aluminosilicate Mesoporous Substances Obtained in The Presence of Biotemplates

Supramolecular structures of lecithin occurred to be the template in the synthesis of mesoporous aluminosilicates; using of various combinations of lecithin and cetyltrimethyl-ammonium bromide or octadecylamine as templating agents allowed to obtain mesoporous substances with pores up to 100 Å, as well as biporous materials in aluminosilicate system. In the presence of glucose oxidase and cetyltrimethyl-ammonium bromide combinations aluminosilicate substances with complex porous structure were shown to be formed (pore size distributions exhibited 3 peaks, corresponding 3 effective size of mesopores in the 30–100 Å range). The investigation of sorption of glucose oxidase on obtained aluminosilicate mesoporous substances was carried out, the results obtained allowus to consider such materials as prospect for creation high capable and selective sorbents for biomolecules sorption, as well as active elements of chemical and biosensors.     

Surface tension of lysozyme mixtures with dodecyltrimethylammonium bromide and sodium dodecylsulfate at water/air and water/octane interfaces

The effect of the concentration and composition of lysozyme-surfactant (cationic dodecyltrim-ethylammonium bromide and anionic sodium dodecylsulfate) mixtures on the surface tension at aqueous solution/air and aqueous solution/octane interphases is studied. It is established that the shape of surface tension isotherms for the mixed solutions depends on the character of interactions between the protein and surfactants.