Salt Effect on the Solution Properties of Cationic Gemini/Conventional Surfactants in the Presence of the Nonionic Polymer Hydroxypropylmethyl Cellulose

In this article, we report the salt effect on interaction of a water-soluble polymer hydroxypropylmethyl cellulose (HPMC) with the cationic Gemini surfactant (ethane-1, 2-diyl bis(N,N-dimethyl-N-hexadecylammoniumacetoxy) dichloride, 16-E2-16), and also its monomeric counterpart cetyltrimethylammonium chloride (CTAC) using the tensiometric method. Surface tension of the amphiphiles diminished in the presence of the polymer as well as salts; eventually, the polymer gets saturated with the surfactant and there is no further change of surface tension of the solution. Interaction between the polymer and surfactant starts at the critical aggregation concentration (CAC) that is stronger for 16-E2-16 than CTAC. CAC and critical micelle concentration (CMC) values of the surfactant-polymer binary mixtures at various concentrations of the polymer were determined. CAC as well as CMC of 16-E2-16 are considerably lower than CTAC. The inorganic salts (KCl and KBr) have a considerable influence on the polymer–surfactant interaction.     

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.     

Mixed Micellar Properties and Related Interaction Parameters of Butanediyl-1,4-bis(dodecyl dimethyl ammonium bromide) Gemini Surfactant with Nonionic Amphiphiles

Mixed micellization of cationic gemini surfactant butanediyl-1,4-bis(dimethyldodecylammonium bromide) with nonionic surfactants (sorbitan esters, alcohols and phenol ethoxylates) and triblock copolymers has been studied tensiometrically. Various physicochemical parameters of the studied systems including ideal CMC values, experimental and ideal micellar compositions, interaction parameters, activity coefficients of the components, etc. have been evaluated by considering theoretical models of Clint, Rubingh, Rosen and Maeda. The experimental critical micelle concentration (CMC) values of the mixed micelles were lower than the CMC values of the individual components and showed a negative deviation from ideal CMC (CMC*) values. The analysis reveals that the mole fractions of gemini are lower compared to the nonionic surfactants/triblock polymers and the values of ΔG _m ^° , ΔG _ad ^° , G _min and ΔG _ex ^m show that the spontaneity of the studied mixed micelles relatively decreases as the content of the gemini in the bulk phase increases.     

Gemini表面活性剂的性质研究

Gemini表面活性剂通常是由两（或三）条疏水链、两个亲水基和一个连接基组成的两性分（离）子,与由单亲水基和单疏水链构成的传统表面活性剂分（离）子相比较,在临界胶团浓度、界面性质等方面有着独特的性质。详述了该类新型表面活性剂的性质,比较了与传统表面活性剂的差别。     

Effects of Spacers on Surface Activities and Aggregation Properties of Anionic Gemini Surfactants

This present article employs four anionic Gemini surfactants with different spacer groups and investigates their physicochemical and aggregation properties. The critical micelle concentration (CMC), surface tension at CMC (γ_CMC) and C ₂₀ of these surfactants have been investigated using the du Nouy ring method. The aggregation number (N) was determined with intrinsic fluorescence quenching method using pyrene as a fluorescence probe and benzophenone as a quencher. Results show that these anionic Gemini surfactants have lower CMC and C ₂₀ values compared with those conventional ones and show higher surface activity. As expected, the spacer plays an important role in the aggregation properties of Gemini surfactants. Under experimental conditions, Gemini B–D with an alkoxylated group as spacer has a lower CMC and a higher aggregation number than Gemini A with methylene as spacer. For Gemini B–D, the CMC and aggregation number values decrease with the increasing flexible spacer length. The micropolarity also affects the aggregation of the present anionic Gemini surfactants. The micropolarity of micelle becomes low when the concentration of surfactants increases. Aggregation numbers of surfactants increase and fluorescence intensities decrease with the increasing concentration of NaCl. These results will help us to understand the relationship between the architectures of Gemini surfactants and their various properties in aqueous solution. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.

Surface Properties and Solubility Enhancement of Anionic/Nonionic Surfactant Mixtures Based on Sulfonate Gemini Surfactants

As a class of novel surfactants, Gemini surfactants usually exhibit fairly excellent interfacial properties in aqueous solutions on account of the unique structure. They have significant application and development potential for industrial production. However, the mixing properties of Gemini surfactants with conventional surfactants are the key to their application. The equilibrium surface tension curves of anionic/nonionic surfactant mixtures based on the sulfonate Gemini surfactant (SGS-12) were measured using the Wilhelmy Plate method. The parameters of surface adsorption, the interaction parameters between anionic and nonionic surfactants, and the thermodynamic parameters of micelle formation were calculated from the corresponding equations. In addition, the dynamic surface tension (DST) curves of anionic/nonionic surfactant mixtures were examined through bubble profile analysis, and the diffusion performance parameters were acquired from empirical formulas. The solubilization of pyrene in micelle solutions was studied using UV–vis absorption spectroscopy. The results show that the interaction parameters of all anionic/nonionic surfactants are negative, indicating that there is a synergistic effect on reducing the surface tension. For the SGS-12/OP-10, SGS-12/Tween 80, SGS-12/AEO9, and SGS-12/APG0810 mixtures, the optimum mixing ratios are 6:4, 7:3, 7:3, and 8:2, respectively. The thermodynamic data of micelles show that the formation of mixed micelles for SGS-12/APG0810 mixtures is an enthalpy-driven process. The tendency of DST curves of the SGS-12/APG0810 mixture is similar to that of SGS-12. In comparison with single-surfactant solutions, the anionic/nonionic surfactant mixtures show stronger solubilization capacity toward pyrene.     

一种不对称阴离子Gemini表面活性剂的合成及表面活性研究

以α-溴代十四酸乙酯和4-癸基苯酚为原料,经Williamson醚化、磺化及皂化反应制备了一种不对称阴离子Gemini表面活性剂α-(4-癸基-2-磺基)-苯氧基十四酸钠,简写为C12CO2Na-p-C10SO3Na,考察了醚化反应条件,并用FTIR和1HNMR表征了中间体及目标产物结构。结果表明,醚化反应的最佳条件为:以N,N-二甲基甲酰胺(DMF)和甲苯作溶剂,无水K2CO3作缚酸剂,物料比n(α-溴代十四酸乙酯)∶n(4-癸基苯酚)=1.05∶1,回流反应3 h,醚化产物收率为77.2%(以4-癸基苯酚计)。采用吊片法测定了目标产物的表面活性,其表面张力最低可降至26 mN/m左右,临界胶束浓度(CMC)为3.28×10-6mol/L,比相应常规单链表面活性剂十四烷酸钠和间癸基苯磺酸钠的CMC低3个数量级,体现出Gemini表面活性剂优异的表面活性。     

Synergisms in Binary Mixtures of Anionic and pH‐Insensitive Zwitterionic Surfactants and Their Precipitation Behavior with Calcium Ions

This work aims to investigate synergy in anionic and zwitterionic surfactant mixtures, as they result in better interfacial properties and micellization behavior. Various mixtures of the pH‐insensitive zwitterionic surfactant 3‐(decyldimethylammonio) propanesulfonate (Zwittergent 3–10) and sodium dodecylsulfate (SDS) were prepared in aqueous solution at a range of pH values between 2 and 13. The thermodynamic parameters during mixed surfactant adsorption at the air/water interface are obtained and the results show the mixed surfactant systems having superior properties to the constituent surfactants. Experimentally, the mixed surfactant solutions clearly improve the surface activities by lowering the critical micelle concentration (CMC) and lowering the surface tension at the air/water interface. The synergisms are investigated through the interaction parameters estimated from regular solution theory that is used to quantitatively describe the nonideality of surfactant mixtures. High negative interaction parameters are obtained from these surfactant mixtures. Experimental precipitation phase boundaries of SDS in the presence of CaCl₂ were also investigated in mixtures containing pH‐insensitive zwitterionic surfactant at different pH levels from 2 to 13 and SDS mole fractions of 0.25, 0.50, 0.75, and 1.00. Changes in the precipitation phase boundaries are due to the changes in the speciation or activities of the major components both below and above the CMC. As a result, the precipitation phase boundaries are pH dependent. In addition, mixed micellization and counterion binding to the micelle also change the precipitation phase boundary above the CMC. The activity‐based solubility product of calcium dodecylsulfate is also determined from the precipitation phase boundaries below the CMC. X‐ray diffraction patterns and SEM images confirm that only calcium dodecylsulfate precipitates in the soap scum for all pH and surfactant compositions studied.     

Micellization Studies of Dicationic Gemini Surfactants (m-2-m Type) in the Presence of Various Counter- and Co-Ions

Salts have the ability to influence the water activity and self-association of ionic micelles. In the present case, gemini surfactants; ethanediyl-α,ω-bis(dimethyl alkyl ammonium bromide) (referred to as m-2-m, m = 10, 12, 14) are synthesized and their micellization study in aqueous medium in presence of monovalent inorganic (NaBr, NaNO₃, NaCl, KCl, LiCl) and organic salts (NaTos, NaBenz, NaSal) at 303 K is systematically investigated by conductometric and tensiometric methods. All the salts have the tendency to lower the critical micelle concentration of the surfactants. The effect of inorganic salts on the micellization properties has been found to obey the Hofmeister series. Organic salts reduce the CMC more effectively as compared to inorganic salts. The theoretical models of Rubingh and Rosen have been used to compare the results and obtain the interaction parameters, minimum area per molecule, surface excess, mixed micelle composition, activity coefficients and free energies of micellization/adsorption.     

磺酸盐型双基表面活性剂的合成与表面性能

以壬基酚和甲醛为原料,合成了一种新型的磺酸盐型双基表面活性剂(Gemini-A)。利用元素分析、红外光谱确定了Gemini-A的结构。研究了Gemini-A水溶液的润湿性,比较了Gemini-A与传统表面活性剂的增溶能力。试验结果表明,Gemini-A水溶液具有较低的表面张力(33.51 mN/m)和临界胶束浓度(0.141 mmol/L)及良好的润湿性,显示出了较好的表面性能,具有很强的增溶能力,是符合3次采油要求的表面活性剂。     

可裂解Gemini型季铵盐表面活性剂的合成与性能

合成了一系列可裂解Gem in i型季铵盐表面活性剂:烷基-α,ω-双(二甲基酰氧乙基溴化铵),标记为Ⅱ-m-n(m=12,14;n=3,4,6);采用红外光谱和核磁共振进行结构表征。测定了相关的性能,结果表明,可裂解Gem in i型季铵盐表面活性剂具有很强的胶束生成能力,其临界胶束浓度(CMC)为2.63×10-4~4.17×10-4mol/L(m=12)及2.88×10-5~4.46×10-5mol/L(m=14),分别比相应的单季铵盐表面活性剂的临界胶束浓度(CMC)低两个数量级;其泡沫稳定性、乳化性能和杀菌性明显优于相应的单季铵盐表面活性剂。     

Synthesis,Surface Property and Antimicrobial Activity of Cationic Gemini Surfactants Containing Adamantane and Amide Groups

A series of novel cationic gemini surfactants, namely 1,3-adamantanedicarboxylic acid bis(alkyldimethyl-3-ammoniopropyl amide) dibromide designated as [Ad-2(amC _n )] (n = 12, 14, 16), containing adamantane, two amide groups, and two hydrocarbon chains, were synthesized from 1,3-adamantanedicarboxylic acid. The surface-active properties of the surfactants were investigated through surface tension and electrical conductivity measurement. A series of thermodynamic parameters such as standard free energy \(\left( {\Delta G^\circ_{\text{m}} } \right)\) , enthalpy \(\left( {\Delta H^\circ_{\text{m}} } \right)\) , and entropy \(\left( {\Delta S^\circ_{\text{m}} } \right)\) of micellization were evaluated from electrical conductivity measurements in the temperature range from 288 to 308 K. The micellization for [Ad-2(amC _n )] is entropy-driven at low temperature and enthalpy-driven at high temperature. Further, the antimicrobial activity of the synthesized gemini surfactants against both Gram-positive and Gram-negative bacteria was also investigated, and this study showed that the compound [Ad-2(amC₁₂)] has excellent antibacterial activity against all studied bacteria.     

Properties of a Binary System Containing Anionic and Cationic Gemini Surfactants

Surface tension, fluorescence, and dynamic light scattering were used to investigate the properties of a binary surfactant system comprising an anionic gemini surfactant (DLMC) and cationic gemini surfactant (II‐12‐EO₂). Surface tension measurements afforded the critical micelle concentration (cmc) of the mixture and the values are all lower than those of pure constituent surfactants. For the mixtures of II‐12‐EO₂/DLMC, the micelle aggregation number decreases with the increase of II‐12‐EO₂, and the micropolarity of the micelle is lowest when the molar fraction of II‐12‐EO₂ is 0.5; the hydrodynamic radius (R_h) of the mixed micelle first increases and then decreases with the addition of II‐12‐EO₂, and larger micelles are obtained when the molar fraction of II‐12‐EO₂ is 0.5 or 0.7.     

Physico-Chemical Investigations of Mixed Micelles of Cationic Gemini and Conventional Surfactants: a Conductometric Study

The interaction of cationic gemini and cationic conventional surfactants by conductivity was systematically overviewed, paying attention to synergism observed in micellization. These mixed systems were found to show remarkable synergism in micelle formation. The experimental critical micelle concentration values being lower than the value predicted by ideal solution theory indicate that the mixed micellization is due to attractive interaction between the two components. Gemini/conventional systems form mixed micelle due to attractive interactions (negative β values). The values of micellar mole fraction of constituent 1 (X ₁) in surfactant mixtures are more than in the ideal state (X ₁ ^ideal ), which means that, the mixed micelles are rich in conventional surfactants in comparison to that in the ideal state.     

磺酸型Gemini表面活性剂的合成及表面活性

以壬基酚、1,4-二溴丁烷和氯磺酸为主要原料,通过三步反应合成了新型的磺酸型Gemini表面活性剂9BA-4-9BA,讨论了合成反应时间、温度以及催化剂对产物纯度和产率等因素的影响,优化了反应过程。利用核磁共振谱和红外光谱表征了产物结构,并通过DCTA21表面/界面张力仪测试其水溶液中的表面张力。和传统表面活性剂相比,合成的Gemini表面活性剂9BA-4-9BA具有更高的表面活性,其临界胶束浓度和C20分别为6.2×10-4mol/L和1.1×10-5mol/L。     

Synthesis and Surface Properties of Anionic Gemini Surfactants having N-acylamide and Carboxylate Groups

A straightforward synthetic strategy to an anionic gemini surfactant having both N-acylamide and carboxylate groups in a molecule has been demonstrated. The surface properties of the anionic gemini surfactant, such as CMC (critical micelle concentration), C₂₀ (the concentration required to reduce the surface tension of the solvent by 20 mN/m), γ _CMC (the surface tension at the CMC), ∏ _CMC (the surface pressure at the CMC), Γ _max (the maximum surface excess concentration at the air/aqueous solution interface), A _min (the minimum area per surfactant molecule at the air/water interface), and the CMC/C₂₀ ratio (a measure of the tendency to form micelles relative to adsorbtion at the air/water interface), have been studied. The influence of the different concentrations of NaCl on the surface properties of the gemini surfactant has been discussed. The results have shown that the CMC values decreased with an increase in the concentration of NaCl indicating that the Na⁺ preferentially adsorbs onto the surface of the charged aggregate and facilitates the aggregate growth by suppressing the main impediment of electrostatic repulsion among head groups. Additionally, the values of Γ _max are always higher in salt solutions as compared to those in pure water due to their salting out effect. The larger pC₂₀ value indicates that the surfactant adsorbs more efficiently at the air/water interface and reduces surface tension more efficiently. In addition, the geminis in water show little or no break in their specific conductance versus surfactant molar concentration plots. This is attributable to protonation of the carboxylate group and strong Na⁺ release during micellization.     

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.     

Synthesis,Surface and Antimicrobial Activities of Cationic Gemini Surfactants with Semi-Rigid Spacers

Four cationic gemini surfactants featuring semi-rigid spacers were synthesized via a two-step process. The surface-active properties of these surfactants were investigated through surface tension and electrical conductivity measurement. The thermodynamic parameters of micellization were evaluated from electrical conductivity measurements at temperatures ranging from 293 to 313 K. The aggregation behavior of these synthesized gemini surfactants in water were investigated using dynamic light scattering and transmission electron microscopy. Further, the antimicrobial activities of these synthesized gemini surfactants against both Gram-positive and Gram-negative bacteria were also investigated.     

稳态荧光法测定Gemini水溶液聚集性质

用稳态荧光法测定合成的Gemini阴离子表面活性剂水溶液的聚集性质,并与其它方法如电导法、表面张力法测定的结果进行对比,结果吻合,表明荧光法作为一种测定Gemini阴离子表面活性剂水溶液聚集性质的方法是可行的,并对Gemini和单基表面活性剂在临界胶束浓度Ccmc前后荧光相对强度变化规律做了简要分析。     

A Mathematical Approach to a More Accurate Determination of Critical Micelle Concentration and Other Thermodynamic Parameters of 14‐2‐14 Gemini Surfactant in Water–Organic Solvent Mixed Media at Variable Temperatures

To explore how the solvent characteristics influence the self‐aggregation of the cationic gemini surfactant dimethylene‐1,2‐bis(tetradecyldimethylammonium bromide) (14‐2‐14) and to obtain various energetic parameters, conductometric experiments were performed on the binary mixtures in the presence of commonly used organic solvents; formamide (FA), acetonitrile (AN) and 2‐methoxyethanol (ME) in aqueous solutions at varying temperatures (298.15–323.15 K) and compositions. The procedure suggested by Carpena et al. has been utilized to analyze conductivity–concentration plots in order to obtain critical micelle concentration (CMC) and degree of counterion dissociation (α) of the micelles. This method provides more accurate results as compared to conventional treatments, and the experimental error for the evaluation of micellar parameters is reduced significantly. The results revealed that, although the process of micellization becomes less favorable with the increase in composition of FA, AN and ME in mixed systems, the increase in CMC at compositions lower than 20% (v/v) of the organic solvents is relatively less, indicating that water character is dominant in the bulk phase. As the enthalpy of micellization became more negative, the corresponding entropy change became less positive and enthalpy–entropy compensation phenomenon has been observed for 14‐2‐14 in all the mixtures within the studied temperature range.