Conductometric and spectrophotometric studies on chromium soap solutions in benzene-dimethyl formamide

Critical micelle concentrations, degrees of dissociation, and dissociation constants of chromium soaps (laurate, myristate, palmitate, and stearate) in a mixture of benzene and dimethyl formamide (7:3, vol/vol) were determined from conductivity measurements. The soaps behave as simple moderate electrolytes in dilute solutions. Critical micelle concentration, limiting molar conductance and dissociation constants decreased with increasing numbers of carbon atoms in the soap molecules. Spectrophotometric results show that metal-to-oxygen bonds in chromium soaps are not purely ionic but have some covalent character.     

Evaluation of mixed micellar interactions of CnBCl and SDBS mixtures using dissociated Margules model and influence of different salts

The conductivity measurement has been used to determine the first and second CMC's (CMC₁ and CMC₂) of alkyldimethylbenzylammonium chloride (C_nBCl; n = 12, 14 and 16) as well as gemini surfactant trimethylene-1,2-bis-(dodecyldimethylammonium bromide) (12-2-12) with sodium dodecylbenzenesulphonate (SDBS) in aqueous solutions using Rubingh's the regular theory approximation as well as the dissociated Margules Model. The use of Margules model allows us to calculate activity coefficients of the constituents and hence provides better values of micellar parameters for asymmetric mixed systems as compared to the regular solution theory. The CMC₁ values for C_nBCl/SDBS mixtures were seen to be lower than those predicted from their ideal mixtures suggesting synergistic interactions although the synergism increases with chain length (n) of the cationic surfactant. Both CMC₁ and CMC₂ experience a decrease with rising values of n. The addition of salts including NaCl, KCl, NaBr, Na₃PO₄, and Na₂SO₄ in mixtures of C₁₆BCl and SDBS suggests that salt counterions have a considerable impact on CMC₁ when either surfactant is in excess. Zeta potential (ζ) measurements provide more evidence in favor of these observations. The thermodynamic features of micellization have also been scrutinized using isothermal titration calorimetry (ITC).     

Thermodynamics of dissociation and micellization of sodium, calcium, aluminum, and tin stearates in mixed organic solvents

Sodium, calcium, aluminum, and tin stearates behave as weak electrolytes in dilute solutions (60% benzene + 40% methanol, vol/vol) below the critical micelle concentration, and conductance data can be explained on the basis of Ostwald’s formula and the Debye-Hückel theory of weak electrolytes. Dissociation constants and thermodynamic parameters for dissociation and micellization of these soaps were also evaluated. Micellization was spontaneous and predominant over the dissociation process.     

Surface and thermodynamic studies of N-alkkyl N-trimethylsilane ammonium chloride surfactants

N-Dodecyl N-trimethylsilane ammonium chloride, N-tetradecyl-N-trimethylsilane ammonium chloride, N-hexadecyl-N-trimethylsilane ammonium chloride, and N-octadecyl-N-trimethylsilane ammonium chloride were prepared. Surface properties, particularly critical micelle concentration (CMC), effectiveness, maximum surface excess, and minimal surface area, were determined at different concentrations at 20, 35, 50, and 65°C, respectively. From electrical conductivity data, degrees of dissociation and dissociation constants at various concentrations were determined. Free energies, enthalpies, and entropies of micellization and adsorption of the surfactants in aqueous solution were studied.     

Conductometric investigations of zirconyl soaps in a xylene-methanol mixture

Conductometric measurements of solutions of zirconyl soaps in xylene-methanol (4:1, vol/vol) mixture were carried out at 30–50°C, and the results were used to determine the degree of ionization, ionization constant, and various thermodynamic parameters for both ionization and association processes. The results show that the soaps behave as weak electrolytes in dilute solutions, and the concentrations at which aggregation commences increased with increasing temperature and decreasing chainlength of the soap molecules.     

Composition of mixed anionic/nonionic surfactant micelles

A proposed method of determining the composition of mixed micelles in equilibrium with monomer of known composition is described. The systems were sodium dodecyl sulfate-polyoxyethylene 23 lauryl ether (Brij 35) in water and in 0.1 M sodium chloride solution at 25°C. This technique applies the Gibbs-Duhem equation to the mixed micelle, which is treated as a pseudophase. This proposed methodology which needs only critical micelle concentration data as a function of monomer composition, is applied to an anionic/nonionic surfactant pair. The calculated monomer-micelle equilibrium is found to be very similar to the much-used regular solution for nonideal systems.     

Mixed-surfactant system of dodecylbenzene sulfonate and alpha-olefin sulfonate: Micellar and volumetric studies

Critical micelle concentrations of sodium salts of dodecylbenzene sulfonate, alpha-olefin (C₁₆) sulfonate, and their mixtures have been evaluated by measuring the surface tensions of solutions at 298.15 K. Interaction parameters for mixed monolayer formation (β^σ) and mixed-micelle formation (β^M) have been calculated from the critical micelle concentration data. Densities of solutions of surfactants and their mixtures were measured with a vibrating-tube densimeter at 298.15 K. Apparent and partial molar volumes have been evaluated from solution density data. Results of the micellar properties have been eplained on the basis of a nonideal multicomponent mixed-micelle model. The mixed-surfactant system exhibits synergism in all aspects when the mole fraction of alpha-olefin sulfonate in the mixture is 0.2. Volumetric properties correlate well, as the partial molar volumes also show a minimum at the same composition of the mixture. Formation of a compact mixed micelle at this composition has been envisaged.     

1,2-丙二醇水溶液在不同温度下的超额摩尔体积黏度和热容

Experimental densities, viscosities and heat capacities at different temperatures were presented over the entire mole fraction range for the binary mixture of 1,2-propanediol and water. Density values were used in the determination of excess molar volumes, VE. At the same time, the excess viscosity was investigated. The values of VE and E were fitted to the Redlich-Kister equation. Good agreement was observed. The excess volumes are negative over the entire range of composition. They show an U-shaped-concentration dependence and decrease in absolute values with increase of temperature. Values of E are negative over the entire range of the composition, and has a trend very similar to that of VE . The analysis shows that at any temperature the specific heat of mixture is a linear function of the composition as x1 > 20%. All the extended lines intersect at one point. An empirical equation is obtained to calculate the specific heat to mixture at any composition and temperature in the experimental range.     

对二甲苯和醋酸二元液体混合物在不同温度下的超额摩尔体积、粘度和热容

Experimental densities, viscosities and heat capacities at different temperatures were presented over the entire range of mole fraction for the binary mixture of p-xylene and acetic acid. Density values were used in the determination of excess molar volumes, VE. At the same time, the excess viscosity and excess molar heat capacities were calculated. The values of V^E, η^E and cE/p were fitted to the Redlich-Kister equation. Good agreements were observed. The excess molar volumes are positive with a large maximum value located in the central concentrationrange. The excess viscosity has an opposite trend to the excess molar volume V^E. η^E values are negative over the entire range of the mixture. The cure of dependence of c E/p on concentration has a special shape. The molecularinteraction between v-xvlene and acetic acid is discussed.     

Excess Molar Volume, Viscosity and Heat Capacity for the Binary Mixture of p-Xylene and Acetic Acid at Different Temperatures

Experimental densities, viscosities and heat capacities at different temperatures were presented over the entire range of mole fraction for the binary mixture of p-xylene and acetic acid. Density values were used in the determination of excess molar volumes, VE. At the same time, the excess viscosity and excess molar heat capacities were calculated. The values of VE, ηE and cpE were fitted to the Redlich-Kister equation. Good agreements were observed. The excess molar volumes are positive with a large maximum value located in the central concentration range. The excess viscosity has an opposite trend to the excess molar volume VE. ηE values are negative over the entire range of the mixture. The cure of dependence of cpE on concentration has a special shape. The molecular interaction between p-xylene and acetic acid is discussed.     

Recent studies of particle packing in organic coatings

Organic coatings often contain sufficient pigmentation that the pigment volume concentration (PVC) and the critical PVC (CPVC) must be carefully considered. Past work has shown that the CPVC can be identified with the random densest packing of pigment particles after considerations of the adsorbed polymer layer on the particles is taken into account, and that this packing can be predicted by empirical particle packing algorithms developed for mixtures of particle sizes. Recent studies have shown that local fluctuations of pigment and polymer concentrations in a film can lead to local film volumes that can exceed the CPVC even though the average PVC for the whole film (the global PVC) is below the CPVC. These effects are consistent with observations of void formation in films below the CPVC, and can be analyzed by local film statistics. We have also recently performed simulations of particle packing by the compression of multiple hard spheres that allows further insight into local concentration fluctuations in PVC within a film.     

The self-aggregation of sodium perfluorooctanoate in aqueous solution at different temperatures

Electrical conductivities of sodium perfluorooctanoate (SPFO) in aqueous solutions were measured at different temperatures (range 294–328 K). Critical micelle concentrations (CMC) and the degree of ionization (α) of the micelles were derived from such data. The results revealed that temperature dependence of CMC is U-shaped with a minimum at 316 K. Gibbs free energies, enthalpies, and entropies of micelle formation as a function of temperature were estimated from the CMC and α values using the charged pseudo-phase separation model. To correlate the enthalpic and entropic contributions, the compensation phenomenon was studied, with a compensation temperature of 309 K and an intercept of −27.7 kJ·mol⁻¹. Apparent molar volumes and adiabatic compressibilities of SPFO were determined from density and ultrasound velocity measurements in the same temperature range as conductivities. Positive deviation from the Debye-Hückel limiting law of the apparent molar volume in the range of temperatures studied evidenced hydrogen bonding-type interactions between monomers and the existence of dimers in the premicellar region. With micellization, the apparent molar volumes decrease with rising temperature, indicating that the structure of micelles is looser than that of monomers. The isentropic apparent molar adiabatic compressibilities following micellization were positive, indicating the predominant role of the decrease in hydrophobic hydration in the association process.     

Surface Activity of Monomeric and Polymeric (3-alkyloxy aniline) Surfactants

ABSTRACT

The adsorption and micellization processes of 3-alkyloxy aniline namely [3-decyloxy aniline (C10M), 3-dodecyloxy aniline (C12M) and 3-cetyloxy aniline (C16M)] and their polymers [C10P, C12P and C16P] have been investigated using surface tension (γ) measurements at different temperatures. The synthesized monomers and polymers have been characterized by IR and elemental analysis. The surface and thermodynamic parameters of these monomeric and polymeric surfactants are investigated. The results show that the critical micelle concentration (CMC) of the polymeric surfactants is lower than that of monomers. The CMC values decreases as the hydrophobic chain lengthens for both monomeric and polymeric surfactants. The surface parameters show the ability of monomeric and polymeric surfactants to adsorb at the air/water interface and decrease the surface tension. The thermodynamic parameters reveal that the micellization process is spontaneous for all investigated surfactants. The specific conductance measurements show that the specific conductance increases with increasing chain length of the substituted alkyl groups, the synthesized polymeric surfactants have higher values of specific conductance than the corresponding monomers and the specific conductance increases with rising solution temperature.     

293.15 K到333.15 K温度下一些氨基酸及其相应基团水溶液中的偏摩尔体积研究

Densities of aqueous solutions of eight amino acids, glycine, L-alanine, L-valine, L-isoleucine, L-serine,L-threonine, L-arginine and L-phenylalanine, are measured as a function of amino acid concentration from 293.15 K to 333.15K. These data are used to calculate the apparent molar volume V and infinite dilution apparent molar volume V0 (partial molar volume). Data of five amino acids are used to correlate partial molar volume V0 using group contribution method to estimate the contributions of the zwitterionic end groups (NH3 ,COO-) and CH2group, OH group, CNHNHNH2 group and C6H5(phenyl) group of amino acids. The results show that V0 values for all kinds of groups of amino acids studied increase with increase of temperature except those for CH2 group,which are almost constant within the studied temperature range. Data of other amino acids, L-valine, L-isoleucine and L-threonine, are chosen for comparison with the predicted partial molar volume V0 using the group additivity parameters obtained. The results confirm that this group additivity method has excellent predictive utility.     

Conductometric studies and thermodynamics of dissociation and micellization of praseodymium and neodymium linoleates in mixed organic solvents

The results show that the praseodymium and neodymium linoleates behave as a weak electrolyte in dilute solutions (60% benzene+40% methanol v/v) below the critical micellar concentration, and the conductance result can be explained on the basis of Ostwald's formula and Debye-Huckel's theory of weak electrolytes. The dissociation constant and thermodynamic parameters for dissociation and micellization processes of lanthanide linoleates are also evaluated. The micellization process has been found to be predominant over the dissociation process.     

无患子皂苷及复配体系表面活性的研究

该文系统地研究了无患子皂苷水提液及其发酵液以及与其他表面活性剂复配体系的表面活性。结果显示,经发酵纯化后的无患子皂苷的高温稳定性、临界胶束质量浓度(CMC)、临界胶束质量浓度时的表面张力(γCMC)、泡沫性能及乳化力都有不同程度的改善;根据Rosen理论推算出无患子皂苷发酵液与脂肪醇聚氧乙烯醚硫酸钠(AES)、十八烷基三甲基氯化铵(1831)、烷基聚葡萄糖苷(APG)、脂肪醇聚氧乙烯醚(平平加)进行二元复配的最佳配比。γCMC、CMC及泡沫实验测试结果表明,无患子皂苷发酵液与这4种表面活性剂组成的二元复配体系都有不同程度的协同增效效应;乳化力测试结果显示,无患子皂苷与APG复配对棕榈油和液体石蜡都有较大的协同增效作用,但其他3种复配体系仅对棕榈油有协同增效作用,对液体石蜡无协同增效作用。     

双基表面活性剂的性质与结构的研究

二聚(dimeric)和齐聚(oligomeric)表面活性剂是一类新一代的表面活性剂,在基础研究和生产实践中已逐步走向成熟。本文从最新的研究成果出发,着重于临界胶束浓度(critical micelle concentration,标记为Ccmc)和微观胶束结构两个方面,采用比较的观点和方法,阐述异揭示了其内在的规律和研究与应用前景。     

Thermodynamic study of the dimerization equilibrium of methylene blue, methylene green and thiazole orange at various surfactant concentrations and different ionic strengths and in mixed solvents by spectral titration and chemometric analysis

The monomer-dimer equilibrium and thermodynamics of ionic dyes were investigated by spectrophotometric and chemometric methods. The dimerization constants of methylene blue, methylene green and thiazole orange have been determined by studying the dependence of their absorption spectra at different concentrations of surfactants, ionic strengths and mixed solvents by means of UV-visible spectroscopy in aqueous solutions. The processing of the data, performed for the quantitative analysis of pure spectral profiles, was based on the simultaneous resolution of the overlapping bands in the whole set of absorption spectra. Utilizing the van’t Hoff relationship, which describes the dependence of the equilibrium constant on temperature, as a constraint we determined the spectral responses of the monomer and dimer species as well as the enthalpy and entropy of the dimerization equilibrium. The exciton theory was used for the elucidation of the angle between the monomer units and the interaction energy between the molecules of the dimers.     

Nuclear magnetic resonance studies on hydrolysis kinetics and micellar growth in solutions of surface-active betaine esters

A series of surface-active betaine esters of medium- to long-chain alcohols has been synthesized. The hydrophobic parts used were decyl, dodecyl, tetradecyl, and oleyl chains. Ethyl betainate was prepared as a non-surface-active reference compound. The surfactants were characterized by critical micellization concentration (CMC), and base-catalyzed hydrolysis was studied by using ¹H nuclear magnetic resonance (NMR). Micellar catalysis was shown to have a strong influence on the hydrolysis. This means that the hydrolysis rates are concentration dependent. For dodecyl betainate, the effect of the degradation products (dodecanol and betaine) on the micellar shape was investigated by NMR diffusion experiments. The degradation products were shown to induce micellar growth.     

Synthesis,stability, and biodegradability studies of a surface-active amide

A homolog pure nonionic surfactant, tetra(ethylene glycol) mono-n-octaneamide, was synthesized. The surfactant was characterized by determining the critical micelle concentration, cloud point, and biodegradation. Hydrolysis catalyzed by an acid, an alkali, a peroxide, and enzymes [peptidase from porcine, amidase from Pseudomonas aeruginosa, and two lipases, Mucor miehei lipase (MML) and Candida antarctica lipase B (CALB)] was investigated using ¹H nuclear magnetic resonance. The surfactant was stable toward the acid, alkali, and peroxide. When subjected to peptidase and CALB, the amide was cleaved, although at a low rate. No reaction was obtained when using the amidase or MML. The biodegradation test resulted in more than 60% degradation after 28 d. Based on these results, the amide surfactant can be considered chemically stable, yet highly biodegradable, which generally is an ideal combination of properties for a surfactant.