The Effect of Ethanol on Nanostructures of Mixed Cationic and Anionic Surfactants

Micellization of tetradecyl trimethyl ammonium bromide (TTAB) and sodium dodecyl sulfate (SDS) in water–ethanol (ET) micellar solutions, with the weight percent of ET changing within the range 0–30, was studied by means of surface tension and conductivity measurements. Surface tension measurements also provided information about the dependence of the surface excess concentration, the minimum area per surfactant molecule, and the standard Gibbs energy of adsorption on the added weight percent of the organic solvent. Information about the degree of counterion dissociation and phase transition was obtained through conductivity measurements. Cyclic voltammetry (CV) and dynamic light scattering (DLS) was also employed to investigate the mixed micellar behavior of the binary mixtures. It was shown that an excess of cationic surfactant and ET resulted in a phase transition of vesicles and large micelles to mixed micelles. The regular solution theory approximation was used to determine various micellar parameters of ideal systems. The regular solution interaction parameter (β) suggests that the formation of mixed micelles is due to the synergistic interactions in the case of TTAB/SDS systems and becomes affected by the water/ET ratio.     

表面张力和表面吉布斯自由能的严格证明

表面张力和表面吉布斯自由能是界面现象中非常重要的两个概念,表面张力定义为垂直作用在单位长度界面上的力,而表面吉布斯自由能是定温定压条件下,增加单位表面积引起系统吉布斯自由能的增量,实际上它们是从不同角度观察表面现象的同一物理量,但各教材中基本上没有详细的论述。文章从吉布斯自由能的实际意义角度对两者同一性进行严格的证明。     

Synthesis and evaluation of new amphiphilic polyethylene glycol-based triblock copolymer surfactants

We report in this investigation the synthesis of a new series of amphiphilic ABA-triblock copolymers consisting of double-chain hydrophobic moieties (A) of different chain lengths attached to each end of polyethylene glycols of different molecular weights (B). The identities of the prepared compounds were confirmed by elemental and Fourier transform infrared analyses. The prepared compounds showed good water solubility. Some of their surface properties, such as the critical micelle concentration, effectiveness of water surface tension reduction, surface excess concentration, standard free energies of adsorption and micellization, and surface area per molecule, were determined.     

Adsorption Behavior of Trimethylolpropane-Dehydroabietic Acid Ester at the Air–water Interface

A novel amphipathic trimethylolpropane-dehydroabietic acid ester was successfully prepared with acyl chloride method. Various analytical techniques such as liquid chromatography–mass spectrometry, Fourier transform infrared spectrometry, proton and carbon nuclear magnetic resonance spectroscopy were employed to evaluate the chemical structure of the ester. The surface properties of the ester were investigated by surface tension and resonance light-scattering techniques. The surfactant molecules are adsorbed at the water–air interface in different adsorption states, i.e., state 1 and 2. The dynamic adsorption behavior was studied by combining experimental results and a reorientation model. The molar fraction of solvent decreased, while the molar fraction of surfactant molecules increased with increasing ester concentration at the surface layer. The adsorption value of state 1 presented a unimodal shape and the adsorption value of state 2 presented an s-shape with the increase in surface pressure. The free energy of adsorption is ?36.06 kJ mol^?1, more negative than the free energy of micellization (?29.69 kJ mol^?1), it is actually easier for surfactant molecules to adsorb on the air–water interface.     

Effect of tartrazine dye on micellisation of cationic surfactants: conductometric,spectrophotometric, and tensiometric studies

The interactions between anionic dye (tartrazine) and cationic surfactants (dodecyltrimethylammonium bromide and cetyltrimethylammonium bromide) have been studied by conductometric, spectrophotometric, and tensiometric techniques. The conductance and surface tension of dodecyltrimethylammonium bromide and cetyltrimethylammonium bromide in pure water as well as in aqueous tartrazine when plotted with surfactant concentration gave values of the critical micelle concentration at different temperatures. As well as increasing the length of the carbon chain of surfactants, the presence of tartrazine reduces the critical micelle concentration. From specific conductivity data, the counterion dissociation constant, standard free energy, enthalpy, entropy of micellisation, surface excess concentration, surface tension at critical micelle concentration, minimum area per molecule, surface pressure at critical micelle concentration, and Gibbs energy of adsorption were evaluated. Spectroscopic studies reveal that the binding of dye to micelles brings a bathochromic shift in dye absorption spectra that indicates dye–surfactant interaction.     

Cationic Imidazolium Monomeric Surfactants: Their Synthesis and Surface Active Properties

A series of long-chain ester-based water-soluble cationics have been synthesized by using renewable raw materials like fatty acids and halogenated alcohols. The surface activity of the molecules has been determined by measurement of their conductance and surface tension in aqueous solution. The dynamics of surface activity of these surfactants have also been investigated in the presence of sodium halides (NaCl and NaBr) by surface tension measurement. A series of useful parameters like critical micelle concentration (CMC), surface tension at the CMC (γ_CMC), adsorption efficiency (pC₂₀), effectiveness of surface tension reduction (Π_CMC), Gibbs free energy of the micellization (ΔG _0mic) and Gibbs free energy of adsorption (ΔG _0ads) have been determined from the measurements obtained by surface tension and conductivity methods. Further with the application of the Gibbs adsorption isotherm, maximum surface excess concentration (Γ_max) and minimum surface area/molecule (A_min) at the air–water interface were also estimated. Thermal stability of these long chain cationics have been measured by thermal gravimetric analysis under a nitrogen atmosphere. Analysis of thermal stability measurement indicated that the thermal stability of these long chain imidazoliums increases with an increase in chain length.     

一个基于NRTL方程的液体混合物表面张力模型

A new equation for predicting surface tension is proposed based on the thermodynamic definition of surface tension and the expression of the Gibbs free energy of the system. Using the NRTL equation to represent the excess Gibbs free energy, a two-parameter surface tension equation is derived. The feasibility of the new equation has been tested in terms of 124 binary and 16 multicomponent systems(13-ternary and 3-quaternary) with absolute relative deviations of 0.59~0 and 1.55~0 respectively. This model is also predictive for the temperature dependence of surface tension of liquid mixtures. It is shown that, with good accuracy, this equation is simple and reliable for practical use.     

Surface properties of N-alkanoyl-N-methyl glucamines and related materials

The surface properties [effectiveness of surface tension reduction (γ_CMC) critical micelle concentration (CMC), efficiency of surface tension reduction (pC ₂₀), maximal surface excess concentration (Γ_max), minimal area/molecule at the interface (A _min), and the (CMC/C ₂₀) ratio] of some well-purified N-alkanoyl-N-methyl glucamines and related polyol-based N-methyl amide-type surfactants, having the structural formula RC(O)N(Me)CH₂(CHOH)_xCH₂OH, where RC(O)=undecanoyl, lauroyl, tridecanoyl, myristoyl, and x=1,3, and 4, were investigated at 25°C in distilled water and 0.1 M NaCl. Water solubility of these compounds does not simply depend on the number of hydroxyl groups in the molecule but is associated with the balance between intermolecular hydrogen bonds and hydrogen bonds formed with water molecules. The fundamental interfacial properties, such as CMC and γ_CMC and two thermodynamic parameters, standard free energy of adsorption and standard free energy of micellization, were found to be significantly dependent on the hydrophobic acyl chain rather than on the number of CHOH groups in the hydrophilic moieties. By contrast, the practical performance properties were greatly dependent on the nature of the hydrophilic group. As a whole, these surfactants had desirable foaming properties and efficient wetting abilities. Furthermore, synergism in foaming and wetting abilities was observed in a binary mixture of these surfactants with an alkyloxyethylene sulfate.     

Synthesis,surface active and thermal properties of novel imidazolium cationic monomeric surfactants

A series of long chain water soluble cationics have been synthesized by using renewable raw materials like fatty alcohols and epichlorohydrin. The surface activity of the molecules has been determined by measurement of their conductance and surface tension in aqueous solution. The dynamics of surface activity of these surfactants have also been investigated in the presence of sodium halides, NaCl and NaBr by surface tension measurement. A series of useful parameters like critical micelle concentration (cmc), surface tension at the cmc (γ_cmc), adsorption efficiency (pC20), effectiveness of surface tension reduction (Π_cmc), Gibbs free energy of the micellization (ΔG_0 mic) and Gibbs free energy of adsorption (ΔG_0 ads) have been determined from the measurements obtained by surface tension and conductivity method. Further with the application of the Gibbs adsorption isotherm, maximum surface excess concentration (θ_max) and minimum surface area/molecule (A_min) at the air–water interface were also estimated. Thermal stability of these long chain cationics has been measured by thermal gravimetric analysis under nitrogen atmosphere. Analysis of thermal stability measurement indicated that the thermal stability of these long chain imidazoliums increase with an increase in chain length.     

Determination of Acoustical Parameters of Aqueous Solution of Kolliphors Binary Mixtures Using Density,Speed of Sound,Viscosity, and Surface Tension Measurements

Measurements of density, speed of sound, and surface tension as well as viscosity of aqueous Kolliphor® ELP (ELP) and Kolliphor® RH 40 (RH40) solutions as well as binary mixtures at different surfactant mole fractions were made at 293 K to investigate their aggregation behavior. The free volume, internal pressure, and molar cohesive energy were calculated and compared to the specific acoustic impedance and intermolecular free length to obtain qualitative information about the character of interactions between the surfactant molecules in the mixture through the water phase.     

Physicochemical Studies on the Interfacial and Micellization Behavior of CTAB in Aqueous Polyethylene Glycol Media

Interfacial and micellization behavior of cetyltrimethylammonium bromide (CTAB) have been studied in aqueous polyethylene glycol (PEG) mixed solvent systems of varying concentrations and molar mass. Interfacial behavior of CTAB was investigated by the equilibrium surface tension method. Conductance studies of surfactant solutions under different condition helped in determining the critical micelle concentration (CMC) and degree of dissociation of CTAB micelles. In addition, the limiting molar conductivity of surfactant and micellar species were evaluated from the differential plots. The CMC of CTAB was found to increase with increasing PEG concentration as well as its molar mass, although, the process of interfacial adsorption and micellization was found to be spontaneous, as evidenced by negative free energy change. The viscosity of CTAB micelles in aqueous-PEG mixtures was found to increase with the increase in PEG concentration and molar mass. Dynamic light scattering measurements revealed a size enhancement effect contributed by the PEG oligomers. An increase in the CMC of CTAB and the subsequent presence of a higher number of ionic species in their dissociated form was further established by an overall increase in the zeta potential value in the presence of PEG oligomers. It is proposed that the PEG could wrap around the micelles through their conformational changes. Results also suggest that PEG oligomers could give solvophobic effect which enhances the CMC of CTAB compared to that in pure water.     

复杂含氧盐矿物热力学数据的简单估算方法

提出了一种复杂含氧盐矿物的摩尔生成Gibbs自由能和摩尔生成焓的简单估算方法,并把复杂含氧盐矿物分为不含水复杂含氧盐矿物和含水复杂含氧盐矿物,不含水复杂含氧盐矿物可以看作是酸性氧化物和碱性氧化物组成的物质,其摩尔生成Gibbs自由能或摩尔生成焓都可以看作是酸性氧化物和碱性氧化物复合成的化合物摩尔生成Gibbs自由能或摩尔生成焓之和。含水复杂含氧盐矿物摩尔生成Gibbs自由能或摩尔生成焓是不含水部分和水的摩尔生成Gibbs自由能或摩尔生成焓贡献值之和。本文提出的方法计算步骤十分简单,从相对误差来看,本方法和其他方法相比精度较好,可以计算包含本课题组长期研究的钛酸盐系列晶须的所有复杂含氧盐矿物的摩尔生成Gibbs自由能和摩尔生成焓,为热力学在钛酸盐系列晶须制备中的应用提供理论支持。     

一种计算分子筛标准Gibbs生成自由能的新方法

引 言 自Mobil公司于20世纪60年代成功合成高硅分子筛β[1]及ZSM-5[2]以来,分子筛的合成及其应用便成为催化领域研究的热点.然而,对于分子筛的合成及其改性研究基本上都是凭着研究者的经验,而缺乏理论的有效指导.研究表明,分子筛的热力学性质(如生成焓、生成自由能等)对于分子筛的合成及其性能(如热稳定性等)的预测具有重要的指导意义.但由于分子筛的结构非常复杂,测定分子筛的热力学性质十分困难,到目前为止,只有少数分子筛的某些热力学参数已用实验测定[3].为此,人们一直在探索用各种方法直接计算或预测分子筛的热力学参数.     

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.     

Micellization and Interfacial Interaction Behaviors of Gemini Cationic Surfactants–CTAB Mixed Surfactant Systems

The interfacial and micellization behaviors of binary mixtures of two gemini cationic surfactants and conventional the cetyl trimethyl ammonium bromide surfactant were studied at various molar ratios. From the equilibrium surface tension measurements, the critical micelle concentrations (CMC) data were obtained as functions of the composition. Values of the CMC were analyzed according to the regular solution model developed by Rubingh for mixed micelles. Two interaction parameters were obtained for each system, the interaction at the interface, and in the micellar phase. The results showed that micellization and adsorption properties of the studied mixed systems depend on the spacer chain lengths of the gemini surfactants and their ratio in the mixed systems.     

On the thermodynamic functions of gas-solid adsorption and liquid-solid immersion,and their relation to adhesion,contact angle and surface tension

The thermodynamic functions of gas-solid adsorption and liquid-solid immersion are summarized on a literature basis. For adsorption, the isosteric and calorimetric methods are compared; for immersion, the Gibbs free energy of adhesion as a function of relative pressure is introduced.The thermodynamic functions reported are enthalpy, Gibbs free energy and entropy of adsorption, immersion and adhesion. All the formulae given contain only those values that result from adsorption, immersion, contact angle or surface tension of the liquids measurements.Interrelations between the thermodynamic functions of adsorption, immersion and adhesion are also given. They permit cross checks and substitution of measurements, e.g., of immersion for adsorption measurement.Typical values are reported and plots of some thermodynamic functions versus coverage are discussed with respect to height and decrease of the powder-adsorptive interaction with layer thickness.     

Mixed micelles of binary surfactant mixtures Tween 40 – Na-3,12-dioxo-5β-cholanate and Tween 80 – Na-3,12-dioxo-5β-cholanate and their thermodynamic description and characterization

Regular solution theory (RST) was compared with model-independent thermodynamical methods (MIM) to analyze binary mixed micelles. It was found that if the molar fractions of the surfactants obtained using RST and MIM do not differ, the binary mixed micelles are symmetrical, according to the excess Gibbs energy. The algorithm used to analyze the binary surfactant mixtures, i.e., the method for determining whether the binary mixture of the surfactants is symmetrical and obeys RST, was developed.Binary mixtures of Tween 40 – Na-3,12-dioxo-5β-cholanate (T40-3,12-DOC) and Tween 80 – Na-3,12-dioxo-5β-cholanate (T80-3,12-DOC) were analyzed. Mixed micelles of T40-3,12-DOC were found to be more stable compared with the hypothetical ideal mixed micelles, i.e., they are primarily symmetrical, according to the excess Gibbs energy, but they do not obey RST. Mixed micelles of T80-3,12-DOC were non-symmetrical, according to the excess free energy, and were less stable then the ideal mixed micelles. With the increase in the molar fraction of T80 in the mixed micelle, the micelle became less stable and decomposed into micelles that comprised the building units.     

Wettability of Polymeric Solids by Aqueous Solutions of Anionic and Nonionic Surfactant Mixtures

Measurements of the surface tension (γ _LV) and advancing contact angle () on poly(tetrafluoroethylene) (PTFE) and poly(methyl methacrylate) (PMMA) were carried out for aqueous solutions of sodium decyl sulfate (SDS) and p-(1,1,3,3-tetramethylbutyl)phenoxypoly(ethylene glycol) (TX100) and their mixtures. The results obtained indicate that the values of the surface tension and contact angles of solutions of surfactants on PTFE and PMMA surfaces depend on the concentration and composition of the surfactant mixtures. Calculations based on the Lucassen-Reynders equation indicate that for single surfactants and their mixtures at a given concentration in the bulk phase the values of surface excess concentration of surfactants at water–air and PTFE–water interfaces are nearly the same, so the adsorption of the surfactants at water–air and PTFE–water interfaces should also be the same. However, the adsorption of TX100 and its mixtures with SDS at water–air interface is higher than that at PMMA–water interface, which is confirmed by the ratio of absolute values of molecular interaction parameters at these interfaces calculated on the basis of Rosen approach. If we take into account the hydration of the poly(ethylene oxide) chains of TX100 and acid and base parameters of the surface tension of water it appears that the PMMA surface is covered by the 'pure' water molecules from the solution or molecules connected with the chain of nonionic surfactant. On the other hand, the lack of SDS molecules at the PMMA–water interface may result from the formations of its micelles which are connected with the TX100 chain.