Studies on Solution Behavior of Aqueous Mixtures of Nonionic Polymer in Presence of Cationic Surfactants

The interactions of two gemini surfactants (16–s–16, s = 5, 6) and their conventional counterpart cetyltrimethylammonium bromide (CTAB) with polyethylene glycols (PEG 3000 and PEG 35000) have been investigated using conductivity, steady state fluorescence, viscosity and TEM techniques. The results indicate that there is no interaction between the PEG 3000/CTAB complex at lower polymer concentrations. However, a very weak interaction is observed at higher concentrations (0.5 and 1.0 wt% PEG 3000), while PEG 3000 and PEG 35000 interact with the gemini surfactants. Both critical aggregation concentration (CAC) and critical micelle concentration (CMC) increases with polymer concentration but are independent of the polymer molecular weight. From steady state fluorescence it is found that the addition of PEG results in no drastic decrease in the aggregation number (N) for all surfactants. This suggests that the atmosphere surrounding the polyion-bound micelles, with respect to the influence on the forces acting at the micelle surface, is equivalent to the counterion/water atmosphere surrounding free micelles. The relative viscosity (η _r) results show an enhancement in η _r for all the surfactants. The increase in η _r is quite significant with gemini surfactants. Polymer-surfactant interaction also depends on the polymer molecular weight. Also, the interaction seems to affect both inter polymer–polymer association as well as chain expansion. Additionally the surfactant induced changes in the polymer conformation depicted by TEM study at the micro structural level confirmed previously observed interactions determined by different analytical techniques.     

Mixed Micellar and Interfacial Interactions of a Triblock Polymer (EO37PO56EO37) with a Series of Monomeric and Dimeric Surfactants

The mixed micellar and interfacial properties of mixtures of triblock polymer (TBP) with a series of monomeric (dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, and cetyltrimethylammonium bromide, and dimeric (dimethylene bis[alkyldimethylammonium bromide], m-2-m, where m = 10, 12, and 14) cationic surfactants were investigated using surface tension and viscosity measurements in aqueous solutions at different temperatures. Various physicochemical properties such as critical micelle concentration, mixed micellar mole fraction, interaction parameter, interfacial, and thermodynamic parameters were evaluated. All the binary mixtures exhibit synergistic interactions which increase with temperature and pass through a minimum with the increase in hydrophobic chain length of the cationic surfactants. The contribution of TBP in mixed micelle formation also increases with the hydrophobic chain length of the surfactants. The interfacial and thermodynamic parameters reveal that the adsorption of the surfactant mixtures at the air–solution interface is more favorable than that of micelle formation and the unfavorable enthalpy changes are overwhelmed by favorable entropy changes. Further, the mixtures of TBP with smaller chain length surfactants show a sharp rise in relative viscosity at higher mole fractions of these surfactants.     

荧光探针法研究新型Gemini表面活性剂在水溶液中的聚集行为

以芘为荧光探针、二苯酮为猝灭剂,用稳态荧光探针法测定了新型Gemini表面活性剂的临界胶团浓度(CMC)、胶团聚集数(Nagg)及胶团微极性.研究了Gemini表面活性剂结构和氯化钠浓度对CMC、Nagg、胶团微极性的影响.结果表明,新型Gemini表面活性剂的CMC比常规表面活性剂的CMC低1—2个数量级.当疏水基碳原子数增加时,CMC依次降低,Nagg增大,胶团微极性减小.当氯化钠浓度增大时,Nagg增大,胶团微极性减小.     

双子表面活性剂结构对性能的影响

综述了双子表面活性剂亲水头基的性质、疏水尾基的性质及长度、连接基的性质及长度、反离子等结构参数对其溶解性、表面活性、胶束形状、起泡性及钙皂分散能力等的影响。双子表面活性剂是一类新型表面活性剂,具有临界胶束浓度低、表面活性高、增黏能力强等一系列优异性能,这些优良性能使其具有良好的应用潜力。指出了结构参数对于双子表面活性剂有针对性的应用的重要意义,并展望了这类表面活性剂的应用前景。     

Constructing Gemini‐Like Surfactants with Single‐Chain Surfactant and Dicarboxylic Acid Sodium Salts

Construction of gemini‐like surfactants using the cationic single‐chain surfactant cetyltrimethylammonium bromide C₁₆H₃₃N(CH₃)₃Br₂ (CTAB) and the anionic dicarboxylic acid sodium salt NaOOC(CH₂)_n‐2COONa (C_nNa₂, n = 4, 6, 8, 10, 12) by way of non‐covalent interactions has been investigated by surface tension measurements, hydrogen‐1 nuclear magnetic resonance (¹H NMR) spectroscopy and isothermal titration microcalorimetry (ITC). The critical micelle concentrations (cmc) of the CTAB/C_nNa₂ mixtures are obviously lower than that of CTAB and strongly depend on the mixing ratio. Moreover, the cmc values of the CTAB/C_nNa₂ mixtures decrease gradually with an increasing methylene chain length of C_nNa₂, indicating hydrophobic interaction between the hydrocarbon chains of CTAB and C_nNa₂ facilitates micellization of the mixtures. In particular, the ITC curves and ¹H NMR spectra indicate that the binding ratio of CTAB to C_nNa₂, except C₄Na₂, is around 2:1, i.e., (CTAB)₂C_nNa₂. Additionally, CTAB/C_nNa₂ mixtures are soluble in a whole molar ratio and concentration ranges have been studied, even at the electrical neutralization point. Therefore, these results reveal that highly soluble gemini‐like surfactants are conveniently constructed with oppositely‐charged cationic single‐chain surfactants and dicarboxylic acid sodiums. In an attempt at improving the performance of surfactants this work provides guidance for choosing additives that form gemini‐like surfactants via an uncomplicated synthesis.     

Synthesis and Thermodynamic Properties of Rosin-Based Cationic Gemini Surfactants

A series of rosin-based cationic gemini surfactants with different spacer length (n = 2, 3, 4) were synthesized and characterized. Surface activity and micellization parameters including the critical micelle concentration, the degree of counterion dissociation, and thermodynamic functions of micellization in aqueous solutions have been investigated. Free energy perturbation was performed to study the enthalpy-entropy compensation of the synthesized gemini surfactants in aqueous solutions. The experimental results showed that the micellization of rosin-based gemini surfactants in aqueous solutions is a spontaneous and entropy-driven process. The micellization process was found to follow the entropy–enthalpy compensation phenomenon.     

季铵盐双子表面活性剂与HPC在水溶液中的相互作用

采用稳态荧光和电导方法研究了系列季铵盐阳离子双子表面活性剂C12-S-C12·2Br(S代表亚甲基的个数)与水溶性高分子羟丙基纤维素(Hydroxypropyl cellulose,HPC)在水溶液中的相互作用。实验结果表明:在低于双子表面活性剂自身临界胶团浓度(Critical miceue concentration,cmc)时,在HPC分子上发生了聚集。当E12-S-C12·2Br/HPC体系混合溶液中C12-S-C12·2Br。的浓度达到c2(c2>cmc)时才有表面活性剂自由胶团生成。揭示了临界聚集浓度(Critical aggregation concentration,cac)和C12-S-C12·2Br/HPC体系混合溶液中自由胶团生成浓度c2与系列C12-S-C12·2Br表面活性剂cmc的比例关系及与链接链S的关联。     

Synthesis and Performance of a Multi-Purpose Gemini Precursor and the Derivative Alkylaryl Sulfonate Gemini Surfactants

The phenol–formaldehyde condensation reaction to synthesize a gemini precursor was renewed by using high efficient and environmentally benign resin catalysts instead of protonic acids, and the conversion, yield and selectivity of the reaction were all upgraded from the 60 % by the traditional way to over 90 % by the new way. Three alkylaryl sulfonate gemini surfactants were derived from the above gemini precursor by O-methylation, sulfonation and neutralization, that is, sodium salt of sulfonated bis(2-hydroxy-5-nonylphenyl)methane (SBHNM), sodium salt of sulfonated bis(2-hydroxy-5-dodecylphenyl)methane (SBHDM) and sodium salt of sulfonated bis(2-methoxy-5-nonylphenyl)methane (SBMNM). And their performances in aqueous solution were further investigated. The results show that the three gemini surfactants exhibit higher effectiveness and efficiency in surface tension reduction than a monomeric reference surfactant sodium dodecylbenzene sulfonate (SDBS). Furthermore their critical micelle concentration values are at least one order of magnitude lower than that of SDBS. It is also shown that O-methylation of the hydroxyl group in the gemini precursor is effective at improving the surface activity of the gemini surfactants, such as efficiency in surface tension reduction, foam stability and calcium stability. It is suggested that the synthesized hydrophobic skeleton could be a multi-purpose gemini precursor from which various gemini surfactants could be derived by further hydrophobic or hydrophilic modification.     

Synthesis,micellization and cytotoxic studies of ester-functionalized imidazolium gemini surfactants

The fatty acid-based imidazolium gemini surfactants containing hydroxy-substituted spacers were synthesized and characterized by different spectral techniques. The micellization behavior of product compounds was studied by determining their critical micelle concentration (cmc) values from steady state fluorescence and conductivity measurements. The thermodynamic parameters of micellization of synthesized gemini surfactants confirmed that the micelle formation is a thermodynamically favorable, endothermic and an entropy driven phenomenon. The surfactants were further analyzed for their cytotoxic nature by treating them upon human embryonic kidney cell (HEK-293) line and were found to be significantly low cytotoxic. The interesting features like low cmc values, non-cytotoxic and eco-friendly nature of the gemini surfactants may offer new and more efficient substitutes to the conventional drug delivery systems. Thus the gemini surfactants may serve as promising candidates in the biomedical and pharmaceutical fields.     

Effects of Molecular Structure and Temperature on Micellization of Cationic Ammonium Gemini Surfactants in Aqueous Solution

Micellization of four cationic quaternary ammonium gemini surfactants, having a diethyl ether or hexyl spacer with the alkyl chain lengths of 12 and 16 carbon atoms, was studied using isothermal titration microcalorimetry (ITC) and electrical conductivity measurements in the temperature range from 298.15 to 313.15 K. In this temperature range, where surfactants are normally applied, the temperature almost does not influence the critical micelle concentration (CMC) and the degree of micelle ionization (α) values of the gemini surfactants, and the replacement of a hexyl spacer by a diethyl ether spacer leads to a slight decrease in the CMC and α values. However, as the alkyl chain length increases from 12 to 16 carbon atoms, the CMC values significantly decrease from 0.99–1.19 mM to 0.020–0.057 mM. In particular, the enthalpy of micellization (ΔH_mic ) and the associated thermodynamic parameters show obvious changes with varying temperature and molecular structure. ΔH_mic becomes much more exothermic at higher temperature or for the surfactants with a more hydrophilic spacer. Moreover, the heat capacity change of micellization (ΔC _{P, mic} ) is less exothermic for the surfactants with a more hydrophilic spacer or a longer alkyl chain. The enthalpy–entropy compensation data show that the surfactants with longer alkyl chains have a more stable micellar structure.     

A Systematic Study of Mixed Surfactant Solutions of a Cationic Ester-Bonded Dimeric Surfactant with Cationic, Anionic and Nonionic Monomeric Surfactants in Aqueous Media

A novel cationic biodegradable dimeric (gemini) surfactant, ethane-1,2-diyl bis(N,N-dimethyl-N-hexadecylammoniumacetoxy) dichloride (16-E2-16), containing an ester-linked spacer was synthesized. Its pure and mixed micellization properties with monomeric surfactants cetyl trimethyl ammonium chloride, cetyl pyridinium chloride, sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, cetyl alcohol ethoxylate (20EO) and tert-octylphenol ethoxylate (9.5EO) were investigated by surface tension measurements at 30 °C. The critical micelle concentration (CMC) of 16-E2-16 is well below that of cetyl trimethyl ammonium chloride containing the same number of carbon atoms in the hydrophobic tail per polar head. At different mole fractions of the gemini surfactant, the CMCs of the gemini-conventional binary mixtures were determined and were found to be less than the ideal CMC values in all the cases indicating synergistic interactions. Aggregation number and Stern–Volmer constant, obtained by the fluorescence quenching technique, also support the synergistic behavior of the surfactant systems.     

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

Two new classes of gemini cationic surfactants—hexanediyl-1,6-bis[(isopropylol) alkylammonium] dibromide {in the abbreviation form: C_nC₆C_n[iPr-OH] and C_nC₆C_n[iPr-OH]₂; alkyl: C_nH_{2n + 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.     

二元表面活性剂体系微乳液的相行为及热力学研究

用表面张力法研究了苯乙烯基酚聚氧乙烯聚氧丙烯醚嵌段型非离子表面活性剂(PEP)分别与十二烷基硫酸钠(SDS)、十二烷基三甲基溴化铵(CTAB)复配体系分子间的相互作用,并根据测定的临界胶束浓度(CMC)及正规溶液理论计算了复配体系分子间相互作用参数及分子交换能,考察了表面活性剂、助表面活性剂、温度等因素对复配表面活性剂体系微乳液形成过程的相行为及热力学性质的影响。结果表明,二元组分(PEP+SDS)及(PEP+CTAB)复配体系在胶束中和表面吸附层中的都存在较强的增效作用,体系的能量降低,且前者的增效作用大于后者。(PEP+SDS)/正己醇/正庚烷/水微乳液的W/O微乳区域面积最大,温度对该微乳液的相行为影响很小。在此微乳液形成的过程中,助表面活性剂醇从连续油相进入微乳液界面层的标准自由能变化ΔGs0;标准焓变-ΔHs=0,为无热效应过程,ΔGs是由醇分子的混乱度熵变ΔSs决定的。     

Wetting and adsorption properties of cetyltrimethylammonium bromide and Triton X-100 mixture with short-chain alcohol in polymer–solution–air system

Measurements of the contact angle of the aqueous solutions of Triton X-100 (TX-100) and cetyltrimethylammonium bromide (CTAB) mixture with methanol or propanol on the polytetrafluoroethylene (PTFE) and nylon-6 surfaces were made. On the basis of the obtained results, the Gibbs surface excess concentration of alcohol and TX-100 + CTAB mixture at the polymer–solution and polymer–air interfaces was calculated and compared to that at the solution–air one. The standard Gibbs free energy of alcohol adsorption was determined by different methods. For TX-100 and CTAB mixture, this energy was calculated using the values of critical micelle concentration (CMC) of that mixture, the surface tension and contact angle of aqueous solution of alcohol as well as the surface tension and contact angle of the aqueous solution of TX-100 and CTAB mixture with alcohol at CMC. The polymer–solution interfacial tension, the adhesion tension, and the adhesion work of the studied solutions to the polymer surface were also determined. From the obtained data, it results that the studied solutions can wet completely only the nylon-6 surface and that below alcohol critical aggregation concentration the adsorption of surfactants and alcohols at the polymer–water and water–air interfaces is similar for PTFE and different for nylon-6.     

Synthesis and Properties of Dissymmetric Gemini Surfactants

A series of novel dissymmetric gemini surfactants, [C _m H_2m+1COOC₂H₄(CH₃)₂N(CH₂)₃N(CH₃)₂C₂H₄OOCC _n H_2n+1]Br₂ was synthesized and symbolized as m-s–n. The Krafft temperatures and surface tension curves of the dissymmetric gemini surfactants were measured using an electrical conductivity method and a drop volume method. The low Krafft temperatures indicate very good solubility of these esterquat gemini surfactants. With the increasing numbers of carbon atoms in the hydrophobic alkyl chain, the critical micelle concentration (CMC) and the minimum surface area (A _min) decrease, and the efficiency of surface tension reduction (pc₂₀) increases. With the same numbers of carbon atoms in the hydrophobic alkyl chain, the dissymmetric gemini surfactant has a lower CMC and a smaller A _min than the corresponding symmetric gemini surfactant due to the enhanced hydrophobic interactions.     

季铵盐有机硅双子表面活性剂的合成及性能研究

以丙酮和正己烷为溶剂,聚乙二醇二缩水甘油醚和羟基封端聚二甲基硅氧烷为主要原料在四丁基溴化铵(TBAB)和氢氧化钠(Na OH)的催化下合成环氧基聚醚改性硅氧烷(EPEPS),再与N,N-二甲基长链烷基胺〔C_mH_(2m+1)NH(CH_3)_2〕在无水乙醇溶剂中、盐酸催化下进行季铵化反应,制备季铵盐有机硅双子表面活性剂(mpsi-m),通过FTIR和1HNMR对目标产物进行结构表征,研究m-psi-m中疏水链长度对其表面活性、临界胶束浓度、润湿性能以及乳化稳定性的影响。结果表明,随着疏水链长度的增加,m-psi-m的表面活性和润湿性能下降,临界胶束浓度增大,乳化稳定性增强。     

双子表面活性剂溶液胶束微观结构研究

双子表面活性剂因其高界面活性、低临界胶束浓度、低浓度时增粘效果明显,在清洁压裂液增稠方面潜力巨大。而溶液胶束结构的形态及变化与溶液粘度密切相关,因此准确表征不同浓度下双子表面活性剂溶液胶束微观结构形态及变化特征具有重要理论指导意义。在大量调研表面活性剂溶液胶束结构形态检测方法与表征的基础上,重点阐述了可用于双子表面活性剂溶液胶束微观结构表征的研究方法及其研究发展现状。     

Effect of Hydrophobicity and Temperature on the Interactions in the Mixed Micelles of Triblock Polymers [(EO76PO29EO76) and (EO19PO69EO19)] with Monomeric and Gemini Surfactants

The interactions in the mixed micelles of two triblock polymers, F68 (EO₇₆PO₂₉EO₇₆) and P123 (EO₁₉PO₆₉EO₁₉), with a series of monomeric (dodecyltrimethyl ammonium bromide, tetradecyltrimethyl ammonium bromide and cetyltrimethyl ammonium bromide) and gemini {dimethylene bis(alkyldimethyl ammonium bromide), m-2-m, where m = 10, 12 and 14} cationic surfactants were studied by surface tension and viscosity measurements in aqueous solutions at different temperatures. The mixed micellar and interfacial properties of the binary mixtures were analyzed using Clint, Rubingh, Rosen and Maeda approaches. Both F68 and P123 show weak interactions with the studied cationic surfactants at 298.15 K which become favorable (synergistic) at higher temperatures. Further, the synergistic interactions are more in mixtures of P123 than F68 at higher temperatures. A comparison of the effects of number of EO and PO blocks in triblock polymers on various physicochemical parameters of the mixed micelles has also been made. The unfavorable enthalpy changes are compensated by favorable entropy changes as a result of the hydrophobic effect. The relative viscosity (η _r) studies show that the size of the micelles formed by pure P123 is smaller than those of F68. The values of η _r for the mixed micelles of F68 show significant variation with chain length of gemini surfactants whereas no such effect is seen in mixtures with P123.     

Interfacial Dynamic Properties and Dilational Rheology of Sulfonate Gemini Surfactant and its Mixtures with Quaternary Ammonium Bromides at the Air–Water Interface

The dynamic interfacial properties and dilational rheology of gemini sulfonate surfactant (SGS) and its mixtures with quaternary ammonium bromides (DTAB, CTAB) at the air–water interface were investigated using drop shape analysis. Results suggest that the adsorption process of these surfactants is diffusion-controlled at dilute concentrations, whereas the adsorption mechanism gradually shifts to a mixed kinetic-diffusion control with increasing surfactant concentration. The mixed surfactant system possesses the best surface activity when the molar ratios of SGS/DTAB and SGS/CTAB mixtures are 9:10. The formation of catanionic complexes shields the electrostatic repulsion between surfactant molecules and lowers the electrostatic adsorption barrier. Therefore, SGS/DTAB and SGS/CTAB mixtures exhibit higher adsorption rates than either component alone. The effects of oscillating frequency and surfactant concentration on the surface dilational properties of SGS, DTAB, CTAB, SGS/DTAB, and SGS/CTAB mixtures were also determined. As the oscillating frequency increases, the dilational elasticity of these surfactants gradually increases. The dilational elasticity peaks at a certain concentration, which is less than the critical micelle concentration (CMC). Results show that the dilational elasticity of SGS/DTAB and SGS/CTAB mixtures is higher than that of either component, resulting from the formation of a denser monomolecular adsorption layer at the air–water interface. Our study provides a basis for understanding the interaction mechanism of catanionic surfactant mixtures containing Gemini surfactant at the air–water interface.     

含杂环的阳离子双子表面活性剂合成研究进展

综述了合成含杂环的阳离子双子表面活性剂的研究工作,着重介绍了含咪唑、吡啶、三嗪、四氢吡咯、六氢哌啶和三唑等杂环的阳离子双子表面活性剂的制备方法。同时简单阐述了其临界胶束浓度、表面张力、胶束聚集数等性能,并展望了含杂环的阳离子双子表面活性剂的发展方向。