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.     

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.     

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.     

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.     

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.     

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.     

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.     

高斯多峰拟合用于混合表面活性剂十二烷基硫酸钠和吐温80临界胶束浓度的测量

报道了可见吸收光谱线型的高斯多峰拟合用于混合表面活性剂十二烷基硫酸钠(SDS)和吐温80临界胶束浓度的测定.具体的做法是以碱性品红(Fuchsin)为探针,测量固定浓度的吐温80对一系列浓度的SDS-碱性品红水溶液体系的可见吸收光谱.其光谱特征是碱性品红二聚体吸收峰和单体吸收峰叠合在一起.用高斯多峰拟合实现了体系可见光...     

乙醇-水混合溶剂中尿苷酸浓度与溶液密度的关系

获取尿苷酸溶析结晶动力学参数须测定其溶液浓度变化,针对密度法浓度在线测量技术,研究了乙醇 水混合溶剂中尿苷酸(Uridine 5' monophosphate)质量浓度与溶液密度的关系。20℃条件下,测定了尿苷酸在不同质量分数乙醇 水混合溶剂中的溶解度和溶液密度,以及混合溶剂质量分数一定时的尿苷酸质量浓度和溶液密度。实验结果表明:乙醇 水混合溶剂中,溶液体积与尿苷酸质量浓度具有较高的相关性,可以拟合得到三元溶液体系尿苷酸质量浓度与溶液密度的变化关系式。     

Solubility of propylene gas in octane and various polar solvents

Propene gas solubilities at 101.3 kPa pressure are reported in n-octane, chlorobenzene, acetone, acetic acid, ethyl acetate, n-butanol, N-N-dimethyl formamide (DMF) and ethylene glycol for a range of temperatures. These data, along with data from the literature, were used to show the qualitative effects of unsaturation of the gas component on the solubility in various solvents ranging from non-polar to highly polar and associated solvents. This involved a comparison, when data were available, of the solubilities of ethane, ethylene and acetylene, then of butane, isobutane, isobutylene, trans-2-butene and 1,3-butadiene as well as of propane and propene (propylene). The differences in solubilities could be explained using solubilities expressed as a molecular interaction parameter (mip) and by identifying several different types of molecular interactions. For associating solvents these effects can be summarized as follows: mip of acetylene > mip of ethylene > mip of ethane, also mip of propylene > mip of propane and mip of butadiene > mip of isobutylene≥ mip of trans-2-butylene > mip of butane > mip of isobutane.     

异辛基酚聚氧乙烯醚/十二烷基溴化吡啶混合溶液的表面性质及各组分含量的测定

对不同组成的异辛基酚聚氧乙烯醚(TX-100)和十二烷基溴化吡啶(DDPB)混合表面活性剂在KH2PO4/Na2HPO4缓冲溶液中的表面性质进行了研究,结果表明TX-100和DDPB间存在着较弱的作用。研究结果证实利用高效毛细管电泳法能够较准确地测定该混合体系中各单组分表面活性剂的含量;并能将该方法用于测定TX-100和DDPB的临界胶束浓度。     

Solubility and partial molar volume of N,N-dimethylformamide diethyl acetal in supercritical carbon dioxide: Measurement and correlations

The solubilities of N,N-dimethylformamide diethyl acetal were measured at temperatures ranging from 313 to 353 K and pressures from 7.8 to 13.3 MPa in supercritical carbon dioxide. The measured solubility data were correlated using the Chrastil, Sung and Shim (SS), and Jouyban–Chan–Foster (JCF) semiempirical models. Consequently, the calculated results showed satisfactory agreement with experimental data and differed from the measured values by between 4.56 and 6.10%. The correlated results indicated that the JCF model provided the best fitness. Solubility data were also utilized to estimate the partial molar volume for the compound in the supercritical phase using the theory developed by Kumar and Johnston.