Mixing Behavior of Conventional and Gemini Cationic Surfactants

Micellization behavior of cationic monomeric surfactants, hexadecyltrimethylammonium bromide (CTAB), cetylpyridinium bromide (CPB), cetylpyridinium chloride (CPC), tetradecyltrimethylammonium bromide (TTAB), and dimeric (gemini) cationic surfactant pentamethylene‐1, 5‐bis(hexadecyldimethylammonium bromide) with formula C₁₆H₃₃(CH₃)₂N⁺(CH₂)₅N⁺(CH₃)₂C₁₆H₃₃ · 2Br^?, abbreviated as 16‐5‐16, in mixed states (binary) have been studied by conductivity. The micellar compositions, activities of the components, and their mutual interactions have been estimated from Rubingh's theory. The mixtures show nonideal behavior with favorable interactions.     

Interaction Between GMAC-m-CS and Surfactants: Surface Tension and Conductivity Methods

Glycidyl trimethyl ammonium chloride-modified chitosan (GMAC-m-CS) was synthesized through nucleophilic substitution of GMAC on CS in isopropanol dispersed system, which was characterized by FTIR and ¹H NMR methods. The interaction between GMAC-m-CS and surface active ILs ?1-dodecyl (tetradecyl and hexadecyl)-3-methylimidazolium bromide (C_nmimBr, n = 12, 14, 16) was studied by surface tension and conductivity methods. The amount of C_nmimBr adsorbed on GMAC-m-CS increases first with raising temperature, and then decreases, which reaches the largest amount at 30°C. The amount increases with the increase of alkyl chain length. The surface tension reducing capabilities of GMAC-m-CS/C_nmimBr systems increase with temperature, however, decrease with the increase of GMAC-m-CS concentration. The aggregation processes of C₁₄mimBr in solutions without GMAC-m-CS and with high concentration of GMAC-m-CS were entropy driven; however, it is enthalpy driven in solutions with low concentration of GMAC-m-CS. Based on the analysis of properties of GMAC-m-CS/C_nmimBr, the interaction model of GMAC-m-CS/ILs was proposed.     

Modeling of Equilibrium Adsorption and Surface Tension of Cationic Gemini Surfactants

A series of equilibrium tension models are used to evaluate the adsorption behavior of a novel class of lipoaminoacid gemini cationic surfactants, N^α,N^ω-bis(long-chain N^α-acylarginine)α,ω-dialkylamides or bis(Args). For purposes of comparison, the monomer LAM (the methyl ester of N^α-lauroyl arginine) was also examined. These surfactants are of particular interest for both their low toxicity and biocompatibility. The tension models are based on the Gibbs adsorption isotherm and classified as “ionic” when the surface charge and the electric double layer are accounted for or as “pseudo-nonionic” when the surface charge is ignored. Both model predictions and fitted parameter values are evaluated with respect to physical plausibility and overall goodness of fit to the available tension and density data. In particular, the inferred values for the standard Gibbs free energy of adsorption ΔG°, determined from an equilibrium constant defined on a nondimensional basis, without including artifacts due to an electrostatic contribution, are analyzed. The most reliable values of ΔG° are found with the combined model to range from −110 to −120 kJ mol⁻¹ for the three dimers examined and −80 kJ mol⁻¹ for the monomer. For spacer chain lengths n=3, 6, or 9, the maximum surface area of surfactant adsorption and the maximum free energy of adsorption are observed for the surfactant with the spacer chain length of 6.     

Interactions Between the Cationic Surfactants Bearing Different Polar Head Groups: Interfacial,Conductivity, NMR,and Fluorescence Studies

Interfacial tension (γ), conductivity (κ), nuclear magnetic resonance (NMR), and fluorescence measurements have been carried out to study the mixed interfacial and micellar behavior of cationic surfactants cetyltributylphosphonium bromide (CTBB) and the cetyltrimethylammonium bromide (CTAB). From the γ versus log C _s plots, the values of critical micellar concentration (cmc) and various interfacial parameters were computed. From κ measurements, the equivalent conductivities of the monomers (Λ _mon), the micelles (Λ _mic) states and the degree of counterion dissociation (δ) have been evaluated. The cmc values have been analyzed in the context of the pseudophase separation model and regular solution theory. The interaction parameters, β^m and β^σ, in the mixed micelle as well as in the mixed monolayer, respectively, also have been computed. The self‐diffusion coefficients for the micelles have been evaluated by using NMR spectroscopy. From the fluorescence quenching method, the mean micellar aggregation number (N _agg) of the pure and mixed micelles has been obtained from the slope of the ratio of fluorescence intensities in the absence and in the presence of quencher (ln (I _1,0/I ₁) versus [Q] plots. It was found that the incorporation of CTBB into the mixed micelle decreases the N _agg. The microviscosity of the fluorescence probe Rhodamine (RB) was monitored by using fluorescence polarization measurements. The values of fluorescence anisotropies (r) indicate that the penetration of CTBB monomer into CTAB micelles produced less rigid mixed micelles.     

酰胺基团对Gemini表面活性剂表面活性和聚集行为的影响

本文合成了含酰胺基团和不含酰胺基团的两类Gemini阳离子表面活性剂,测定了其表面活性参数,研究了酰胺基团对表面活性剂的表面活性和聚集行为的影响。结果表明,酰胺基团提高了Gemini阳离子表面活性剂的临界胶团浓度,降低了胶团聚集数,增强了胶团微极性,增大了表面活性剂的饱和吸附量。     

Bulk Properties of Carboxymethylchitosan and Cationic Surfactant Mixtures: Fluorescence and Surface Tension Studies

The interactions between carboxymethylchitosan and alkyltrimethylammoniumbromides were studied in aqueous solution. The dependences of aggregation behavior on surfactant concentration, polyelectrolyte concentration, as well as surfactant chain length were investigated mainly using fluorescence spectroscopy method. The variation of I ₁/I ₃ of pyrene fully characterized the aggregation behavior of the polymer-surfactant complex. Meanwhile, based on that Nile red has the sensitivity to the environmental polarity different to pyrene, the changes of aggregates size and number can be reflected by the fluorescence spectroscopy of Nile red.     

Synthesis,Characterization, and Surface Properties of Cationic Gemini Surfactants

New pyridinium gemini surfactants have been synthesized by esterification of renewable fatty acids with mercaptoethanol furnishing respective esters (mercaptomethyl decanoate, mercaptomethyl dodecanoate, mercaptomethyl tetradecanoate, mercaptomethyl hexadecanoate) followed by their subsequent treatment with 4-dimethyl amino pyridine resulting in the formation of title gemini surfactants: 1-(5-(decanoyloxy)-2-hydroxypentyl)-4-((5-(decanoyloxy)-2-hydroxypentyl)dimethyl ammonio)pyridin-1-ium chloride (9), 1-(5-(dodecanoyloxy)-2-hydroxypentyl)-4-((5-(dodecanoyloxy)-2-hydroxypentyl)dimethyl ammonio)pyridin-1-ium chloride (10), 1-(5-(tetradecanoyloxy)-2-hydroxypentyl)-4-((5-(tetradecanoyloxy)-2-hydroxypentyl)dimethyl ammonio)pyridin-1-ium chloride (11), and 1-(5-(hexadecanoyloxy)-2-hydroxypentyl)-4-((5-(hexadecanoyloxy)-2-hydroxypentyl)dimethyl ammonio)pyridin-1-ium chloride (12). Their identifications are based on infrared, ¹H NMR, ¹³C NMR, distortionless enhanced polarization transfer, co-relational spectroscopy (COSY), and mass spectral studies. Their surface active properties are also evaluated on the basis of surface tension and conductivity measurements. Thermal stability of these long chain cationic gemini surfactants have been measured by thermal gravimetric analysis under nitrogen atmosphere.     

卤化钠对一种新型阳离子表面活性剂动态表面张力的影响

The equilibrium and dynamic surface tension （DST） of the novel cationic surfactant, 3-（p-nonylphenoxy）-2-hydroxylpropyl trimethyl ammonium bromide, abbreviated as RTAB, were studied. The effect of sodium halide such as NaCl, NaBr and NaI on the DST behavior of the RTAB solution below its CMC was studied in detail. Due to the preferential adsorption, the effect of hydration and salting out, the ability to reduce the DST values at the same concentration was in the order of NaI〉NaBr〉NaCl. Attributed to its high surface activity, the equilibrium time of the DST of the surfactant solution was insensitive to the ionic strength.     

Adsorption of Cationic Surfactants on Silica Surface: 1. Adsorption Isotherms and Surface Charge

Adsorption isotherms of cationic surfactant, dodecylpyridinium chloride, on an Aerosil OX50 and isotherms of surface charge against the background of 0.001- and 0.1-M KCl solutions at pH 7 and 9 were measured and analyzed. Different forms of adsorption isotherms of surfactants at low and high electrolyte concentrations are explained from differences in the formation of the surface charge of Aerosil. Comparison of the isotherms of surfactant adsorption and surface charge allowed us to make conclusions about the surfactant orientation and structure of an adsorption layer, as well as to determine the fraction of surfactant molecules in the first and second adsorption layers.     

Novel Cationic Gemini Surfactants Based on Piperazine: Synthesis,Surface Activity,and Foam Ability

A series of novel Gemini surfactants C_n-pi-C_n with piperazine moiety as spacer was synthesized and characterized by IR, ¹H NMR, and mass spectra. Their surface activities were evaluated by surface tension, electrical conductivity, and steady-state fluorescence. The obtained results indicated that the synthesized Gemini surfactants exhibited lower critical micelle concentration (cmc) and surface tension (γ_cmc) compared with traditional surfactants. The steady-state fluorescence measurement and electrical conductivity were recorded to demonstrate the accuracy of cmc values. In addition, the micellization was evaluated using conductivity measurement in the temperature range of 298–308 K. The foamability and foam stability of these Gemini surfactants were also examined. In which, the Gemini surfactant with the shortest chain (C₁₂) showed the best foamability but the poorest foam stability. Hydrophile–lipophile balance and emulsifying ability were studied and a comparatively poor emulsifying ability displayed.     

Effects of Nonionic, Cationic, and Mixed Nonionic-Cationic Surfactants on the Acid-Base Behavior of Phenyl Salicylate

The effects of Brij 35 micelles, CTABr micelles, and mixed Brij 35–CTABr micelles on the acid–base behavior of phenyl salicylate (PST) have been studied in aqueous solution containing 2% v/v acetonitrile. The apparent pK_b (pK^app_b) of PST is decreased by 1.5 pK units with the increase in [Brij 35] from 0 to 0.02 M which is attributed to micellar medium effect. The values of pK^app_b remain almost independent of [CTABr] within its range 0.01–0.03 M. The increase in [CTABr] from 0 to 0.03 M in aqueous solution containing 0.02 M Brij 35 has not resulted in a change in pK^app_b. This shows that the characeristic structural features of nonionic Brij 35 micelles remain essentially unchanged on addition of CTABr under the present experimental conditions.     

支链化阳离子和甜菜碱表面活性剂对聚四氟乙烯表面润湿性的影响

利用座滴法研究了支链化阳离子表面活性剂十六烷基羟丙基氯化铵(C₁₆GPC)和两性离子表面活性剂十六烷基羧酸甜菜碱(C₁₆GPB)在聚四氟乙烯(PTFE)表面上的吸附机制和润湿性质, 考察了表面活性剂浓度对表面张力、接触角、粘附张力、固液界面张力和粘附功的影响趋势. 研究发现, 低浓度条件下, 表面活性剂疏水支链的多个亚甲基基团与PTFE表面发生相互作用, 分子以平躺的方式吸附到固体界面; 支链化表面活性剂形成胶束的阻碍较大, 浓度大于临界胶束浓度(cmc)时, C₁₆GPC和C₁₆GPB分子在固液界面上继续吸附, 与PTFE作用的亚甲基基团减少, 分子逐渐直立, 固液界面自由能(γ_sl)明显降低. 对于支链化的阳离子和甜菜碱分子, 接触角均在浓度高于cmc后大幅度降低.     

Study on Volumetric,Compressibility and Viscometric Behavior of Cationic Surfactants (CTAB and DTAB) in Aqueous Glycyl Dipeptide: A Thermo-Acoustic Approach

This study aims to understand how glycyl dipeptide affected the compressibility, volumetric behavior and viscometric behavior of the cationic surfactants CTAB (Cetyltrimethylammonium bromide) and DTAB (dodecyltrimethylammonium bromide). Information on solute–solute, solute–solvent, and solvent–solvent interactions has been inferred using the quantification of density (ρ), speed of sound (u) and viscosity in aqueous media containing glycyl dipeptide in the temperature range 293.15–313.15 K at an interval of 5 K. The data from the aforementioned research have been used to enumerate numerous volumetric and compressibility metrics that aid in the collection of information about the interactional behavior of the system under consideration. The study suggests that CTAB interacts strongly compared to DTAB with dipeptide, and it also significantly dehydrates glycyl dipeptide. The difference in water–water interactions caused by the loss of hydrophobic hydration of the surfactant molecules upon the addition of cationic surfactants may be the cause of the variation in determined parameters with surfactant concentration. Consideration of the structural rearrangement of molecules that may occur in the system has been used to explain the results of viscosity and computed factors related to viscosity. The patterns of competitive intermolecular interactions in the ternary (dipeptide + water + surfactant) system have been used to analyze the trends of all the parameters. The study may be helpful to understand the stability and structural changes in protein–surfactant systems mediated through various interactions that may be present in the system.     

Water Soluble Cruciforms: Effect of Surfactants on Fluorescence

Brighten up! Adding surfactants to aqueous solutions of three different water‐soluble cruciforms (XF) improves their fluorescence quantum yields. Additionally, changes are observed in the emission wavelength of the XF around the critical micelle concentration (cmc) of the surfactant.

     

The Influence on Interfacial Tension of the Combination of Anionic and Cationic Surfactants: Alkyl Sulfonate/Alkyltrimethylammonium Bromide

Mioellization of aqueous mixture of sodium octyl sulfonate ( C₈As )/ cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfonate (C₁₂As)( CTAB in the presence of sodium bromide has been studied by surface tension measurement. Nonideal solution theory has been used to calculate the molecular interaction parameters (β^M and β^s). The oil-aqueous interfacial tensions of C₁₂As/ CTAB, C₈As/CTAB, C₁₂As/dodecyl trimethylammonium bromide (DTAB) systems were also measured. We studied the influence of the surfactant concentration, surfactant molar fraction ratio, hydrocarbon chain length, added NaCl and alcohol concentration on the interfacial tension.     

阳离子和两性表面活性剂在聚甲基丙烯酸甲酯表面的吸附行为

利用座滴法研究了阳离子表面活性剂十六烷基醚羟丙基季铵盐(C₁₆PC)、十六烷基聚氧乙烯醚羟丙基季铵盐(C₁₆(EO)₃PC)和两性离子表面活性剂十六烷基醚羟丙基羧酸甜菜碱(C₁₆PB)、十六烷基聚氧乙烯醚羟丙基羧酸甜菜碱(C₁₆(EO)₃PB)溶液在聚甲基丙烯酸甲酯(PMMA)表面上的润湿性质, 考察了表面活性剂类型及浓度对接触角的影响趋势. 研究发现: 低浓度条件下表面活性剂分子可能以平躺的方式吸附到固体界面, 且亲水基团靠近固体界面, PMMA表面被轻微疏水化; 在高浓度时则通过Lifshitz-van der Waals 作用吸附, 亲水基团在外, PMMA表面被亲水改性. 聚氧乙烯基团(EO基团)的引入对阳离子表面活性剂的接触角影响不大; 而含有聚氧乙烯基团的两性离子表面活性剂在PMMA界面上以类似半胶束的聚集体吸附, 大幅度降低接触角.     

理想混合表面活性剂表面张力的计算公式及实验验证

采用Newton迭代法, 给出了两种计算二组分表面活性剂理想混合体系表面张力的显函数简捷表达式, 并通过膦氧化物同系物, 季铵盐混合体系, 以及全氟辛酸铵和全氟壬酸铵混合系列表面张力的实验值和数值解对其精确性进行了验证. 结果表明, 两种迭代法都有很快的收敛速度, 表达式的相对误差都在1%之内.     

Molecular Exchanging Energy of Anionic／Cationic Surfactants System on the Surface of Solution

In order to study synergism of the mixed surfactants system with molecular exchanging energy ( ε ), the Lennard-Jones formula has been firstly introduced to evaluate the ε of the mixed system, CH3(CH2)nOSO 3^- /CH3(CH2)nN^ (CH3)3, directly from their molecular structure. The comparison of the calculated and the observed results showed that this method is practical.     

荧光探针法研究连接基团对双子型阳离子表面活性剂聚集行为的影响

利用荧光探针法和表面张力法测定了新型双子型阳离子表面活性剂的临界胶团浓度(cmc)、最低表面张力(γ_cmc)、胶团微极性和胶团聚集数(N_agg),探讨了连接基团对此类表面活性剂在水溶液中聚集行为的影响.结果表明,当连接基团增长时,cmc和胶团微极性增加,γ_cmc增大,N_agg减少,表面活性降低,在溶液中自发形成胶团的能力减弱.