Volumetric studies on binary mixtures of surfactants N,N′-bis(dimethyldodecyl)-1,2-ethanediammonium dibromide and 1-dodecyl-3-methylimidazolium bromide in aqueous solutions

The micellization of the binary mixed surfactants comprising of the Gemini surfactant N,N′-bis(dimethyldodecyl)-1,2-ethanediammonium dibromide and 1-dodecyl-3-methylimidazolium bromide has been studied by measurements of density. The apparent molar volumes were calculated for various surfactant concentrations and used to determine the critical micelle concentrations of the mixed surfactants at various compositions. An attractive effect was suggested by negative deviations of the experimental CMC values from the ideal ones. The Margules equation was applied to evaluate the micelle compositions, the activity coefficients of both components, and the excess molar Gibbs free energies of the mixed micelles. The stability of mixed micelles was shown to be enhanced as compared to those formed by single surfactants from the negative values of the excess Gibbs free energy. The comparison of the results obtained from the volumetric and ITC measurements indicated a reasonable good accordance with each other and confirmed the reliability of both methods for investigation on the properties of the mixed micelles.     

Physico-chemical Investigation of Mixed Micelle Formation Between Tetradecyltrimethylammonium Bromide and Dodecyltrimethylammonium Chloride in Water and Aqueous Solutions of Sodium Chloride

Conductometric measurements have been employed to gain a detailed insight into the interactions between two cationic surfactants, tetradecyltrimethylammonium bromide (TTAB) and dodecyltrimethylammonium chloride (DTAC), in water and in an aqueous solution of sodium chloride. The experimental data were analyzed according to Rubingh’s model within the framework of the pseudophase separation model. The evaluated values of critical micelle concentration (cmc) were found to be lower than their corresponding cmc ^id values, signifying attractive interactions involving both components in the solutions. The micellar mole fractions (\( X_{1}^{\text{Rub}} \)) of TTAB evaluated by Rubingh’s model were always larger than the ideal values (\( X_{1}^{\text{id}} \)), signifying the higher involvement of TTAB in mixed micelles of TTAB and DTAC. Activity coefficients (\( f_{ 1}^{\text{Rub}} \) and \( f_{ 2}^{\text{Rub}} \)) were always below one in all cases signifying synergism in the mixed micelles. All the outcomes point to synergism and attractive interactions in the mixed systems. Values of excess Gibbs energy were evaluated by employing Rubingh’s model (\( \Delta G_{\text{ex}}^{\text{Rub}} \)) and the \( \Delta G_{\text{ex}}^{\text{Rub}} \) values obtained are negative. The values of \( \Delta H_{\text{m}}^{\text{o}} \) and \( \Delta S_{\text{m}}^{\text{o}} \) reveal that hydrophobic interaction is expected to be the binding force between TTAB and DTAC in aqueous media at lower temperatures, while both hydrophobic interactions as well as exothermic interactions are involved at higher temperatures. The interaction forces between the surfactants were found to be enhanced in the presence of NaCl.     

Bulk properties of a liquid phase mixture {ethylene glycol+<Emphasis Type="Italic">tert</Emphasis>-butanol} in the temperature range 278.15–348.15 K and pressures of 0.1-100 MPa. I. Experimental results,excess and partial molar volumes

The densities ρ and coefficients of compressibility k = ΔV/V ₀ of a binary mixture {ethylene glycol (1) + tert-butanol (2)} in the temperature range of 278.15–323.15 K and pressures of 0.1–100 MPa over the entire range of compositions of liquid phase state are measured. Found that the coefficients of compressibility k of the mixture increase both with an increase in the concentration of tert-butanol and with a rise in temperature and pressure. The excess molar volumes of the mixture, apparent, partial molar volumes, and limiting partial molar volumes of the components are calculated. It is showed that the excess molar volumes of the mixture are negative and decrease when the pressure increases. The excess molar volumes are described by the Redlich-Kister equation. The partial molar volumes of ethylene glycol sharply decrease in the range of high concentrations of tert-butanol. The dependences of partial molar volumes of ethylene glycol are characterized by the presence of a region of temperature inversion. The “negative compressibility” of the limiting partial volumes of ethylene glycol is revealed.     

Thermodynamic properties of ibuprofen sodium salt in aqueous/urea micellar solutions at 298.15 K

Thermodynamic, surface and micellar properties of anti-inflammatory drug sodium 2-(4-isobutylphenyl) propionate (sodium salt of ibuprofen (NaIBF)) in aqueous/urea solution were studied by surface tension measurements at 298.15 K in the presence of anionic surfactant sodium dodecylsulfate (SDS). Critical micelle concentration (cmc), surface tension at cmc (γcmc), maximum Gibbs surface excess (Γ_max), minimum surface area per surfactant molecule at the air/water interface (A _min) etc. were determined in pure water as well as in aqueous urea solution. The theories of Clint, Rosen and Rubingh have been applied to describe the interactions between these amphiphiles at the interface and in the micellar solution. Various thermodynamic parameters have been calculated and discussed in detail.     

Measurement and Modeling the Excess Molar Volumes and Refractive Index Deviations of Binary Mixtures of 2-Propanol, 2-Butanol and 2-Pentanol with <Emphasis Type="Italic">N</Emphasis>-Propylamine

The densities, ρ, and refractive indices, n _D, of 2-alkanols (C₃–C₅) with N-propylamine have been measured for the whole range of composition at temperatures from (298.15–328.15) K at 10 K intervals and ambient pressure of 81.5 kPa, using an Anton Paar DMA 4500 oscillating tube densimeter and an Anton Paar Abbemat 500 automatic refractometer. From the experimental data, excess molar volumes \( V_{\text{m}}^{\text{E}} \) partial molar volumes \( \bar{V}_{i} \) apparent molar volumes V _?i and refractive index deviations Δn _D the binary systems consisting of N-propylamine + 2-alkanols (2-propanol, 2-butanol, 2-pentanol) were calculated and \( V_{\text{m}}^{\text{E}} \) and Δn _D values were correlated with the Redlich–Kister polynomial. The effect of temperature and the chain length of the alcohol on the excess molar volumes and refractive index deviations are discussed in terms of molecular interaction between unlike molecules. The excess molar volumes are negative and refractive index deviations are positive over the entire composition range, which indicates strong hydrogen bonding between molecules of the mixtures. A comparative study has been made of the refractive indices obtained experimentally and those calculated by means of the Lorentz–Lorenz, Weiner and Arago–Biot relations. The perturbed chain statistical associating fluid theory (PC-SAFT), simplified PC-SAFT and Prigogine–Flory–Patterson theory were also applied to correlate and predict the density and excess molar volumes of the mixtures.     

Measurement and Calculation the Excess Molar Properties of Binary Mixtures Containing Isobutanol, 1-Amino-2-Propanol,and 1-Propanol at Temperatures of (293.15 to 333.15) K

Densities, ρ, and viscosities, η, of pure isobutanol, 1-amino-2-propanol, and 1-propanol, along with their binary mixtures of {x ₁isobutanol + x ₂1-propanol}, {x ₁1-amino-2-propanol + x ₂1-propanol}, and {x ₁1-amino-2-propanol + x ₂isobutanol} were measured over the entire composition range and at temperatures (293.15–333.15) K at ambient pressure (81.5 kPa). Excess molar properties such as the excess molar volume, V _m ^E , partial molar volumes, \( \bar{V}_{1} \) and \( \bar{V}_{2} \), excess partial molar volumes, \( \bar{V}_{1}^{\text{E}} \) and \( \bar{V}_{2}^{\text{E}} \), thermal expansion coefficient, α, excess thermal expansion coefficient, α ^E, viscosity deviation, Δη, and the excess Gibbs energy of activation, ?G ^E*, for the binary mixtures were calculated from the experimental values of densities and viscosities. The excess values of the binary mixtures are negative in the entire composition range and at all temperatures, and increase with increasing temperature. Viscosity deviations, Δη, are negative over the entire composition range and decrease with increasing temperature. The viscosities of the mixtures were correlated by the models of McAllister, Heric, Hind, Katti, and Nissan. The obtained data were correlated by Redlich–Kister equation and the fitting parameters and standard deviations were determined.     

Interfacial and fluorescence studies of mixed-micelle formation by 1,2-diheptanoyl-<Emphasis Type="Italic">sn</Emphasis>-glycero-3-phosphocholine with cationic surfactants

Interfacial, γ, and fluorescence measurements have been performed to evaluate the synergism in mixed cationic and zwitterionic phospholipid systems, viz. dodecyltrimethylammonium bromide plus 1,2-diheptanoyl-sn-glycero-3-phosphocholine (DHPC), tetradecyltrimethylammonium bromide plus DHPC, and hexadecyltrimethylammonium bromide plus DHPC mixtures. From the γ data the maximum surface excess and minimum area per molecule were computed and it was found that the former decreases and the latter increases with the increase in the fraction of cationic component in the binary mixture. Application of regular solution theory demonstrated that strong synergistic interactions are present which increase with the increase in length of the hydrocarbon tail of the cationic surfactant component. These interactions were considerably less in the monolayers than in the mixed micelles. The aggregation number, N _agg, of DHPC shows a significant decrease upon induction of the cationic component and vice versa. The decrease in N _agg is explained on the basis of an increase in the total polarity of the mixed micelles.     

The Study of Intermolecular Interactions for <Emphasis Type="SmallCaps">dl</Emphasis>-Alanine and Glycine in Aqueous <Emphasis Type="SmallCaps">l</Emphasis>(+)-Arabinose Solutions at Different Temperatures and Ambient Pressure,Using the Volumetric Approach

Density measurements are used to calculate the apparent molar volumes V_φ, limiting apparent molar volumes \(V_{\varphi }^{0}\), limiting apparent molar volumes of transfer, \(\Delta_{\text{t}} V_{\varphi }^{0}\), limiting apparent molar expansibilities, \(E_{\varphi }^{0}\), and hydration numbers n_H, for dl-alanine and glycine in aqueous solutions of l(+)-arabinose at T?=?293.15 to 313.15 K. To obtain the limiting apparent molar volume, the V_φ values are extrapolated to zero molality using the linear form of the Redlich–Meyer equation. Also, the limiting apparent molar volumes of transfer, \(\Delta_{\text{t}} V_{\varphi }^{0}\), for the amino acids, from water to aqueous l(+)-arabinose solutions, are calculated from the \(V_{\varphi }^{0}\) values. The limiting apparent molar expansibility, \(E_{\varphi }^{0}\), values have been obtained from the first derivative of limiting apparent molar volumes with respect to temperature. Also the hydration number, n_H, for both amino acids in the ternary solutions are estimated. Possible solute–solvent interactions in the studied ternary systems are discussed.     

Interaction Between an Active Pharmaceutical Ingredient Ionic Liquid Benzalkonium Salicylate and Small Biomolecules in Aqueous Solution: UV Absorption,Conductivity, and Volumetric Study

UV absorption spectroscopy, electrical conductivity and density experiments have been used to investigate the interactions of some small biomolecules (amino acids/dipeptides) with an active pharmaceutical ingredient in ionic liquid form (API-IL), benzalkonium salicylate (BaSal), in aqueous solution. A number of useful parameters, such as critical micellar concentration (cmc), aggregation number (N_agg) and limiting molar conductivity (Λ₀) of BaSal, standard partial molar volumes (\(V_{2,\phi }^{ \circ }\)), corresponding volumes of transfer from water to aqueous BaSal solutions (Δ_trV^o), standard partial molar expansibilities (\(E_{\phi }^{ \circ }\)), hydration number (n_H) of small biomolecules, as well as the binding constants (K_b) for small biomolecule–BaSal complexes have been evaluated. The dependence of the properties on concentration, temperature and alkyl chain length of amino acids/dipeptides is examined. The results are used to identify the solute–solvent physicochemical interactions occurring in the studied systems.     

Phosphorylation of Pyrimidinophane in the Reversed Micellar Solutions of Cationic and Nonionogenic Surfactants

Reactions of a macrocycle containing three pyrimidine fragments and N,N′-bis(2-methylthio-6-methylpyrimidin-4-yl)-hexamethylenediamine with p-nitrophenyl bis(chloromethyl)phosphinate in the micellar solutions of cetyltrimethylammonium bromide, polyethyleneglycol-600 laurate and their mixture in chloroform was investigated spectrophotometrically. Catalytic activity of micelles depends on their structure, concentration of surfactants, molar fraction of the latter in solution, and structure of the nucleophilic reagent.     

Calculating excess volumes of binary solutions with allowance for structural differences between mixed components

Analytical dependences of a volume’s properties on the differences between the geometric structures of initial monosystems are obtained for binary systems simulated by a grain medium. The effect of microstructural parameter k (the ratio of volumes of molecules of mixed components) on the concentration behavior of the relative excess molar volume of different types of real binary solutions is analyzed. It is established that the contribution due to differences between the volumes of molecules and coefficients of the packing density of mixed components is ~80–100% for mutual solutions of n-alkanes and ~55–80% of the experimental value of the relative excess molar volume for water solutions of n-alcohols.     

Effect of Sodium Dodecylbenzenesulfonate on the Association Behavior of Promethazine Hydrochloride in Aqueous/Electrolyte Solutions at Different Temperatures

The interaction between the amphiphilic phenothiazine drug promethazine hydrochloride (PMT) and an anionic surfactant sodium dodecylbenzenesulfonate has been investigated using the conductometric technique in the absence and presence of an inorganic salt (50 mmol·kg^?1 NaCl) at five different compositions and temperatures. PMT is employed for the cure of allergic symptoms. Different physicochemical parameters such as critical micellar concentration (cmc), thermodynamic, and micellar composition are evaluated and discussed in detail using regular solution theory (RST). The addition of salt decreased the surface charge of micelles, lowering the cmc values of the amphiphile. The interaction parameter (β) is negative at all temperatures and compositions indicating attractive interactions. Due to the presence of NaCl in mixed systems the attractive interaction (β) was further increased (β values more negative). The negative values of Gibbs energy (\( \Delta G^{0}_{\text{m}} \)) of mixing revealed the stability of the solution. Owing to the presence of NaCl, the \( \Delta G^{0}_{\text{m}} \) values are found to be more negative suggesting that the driving force for interaction was significantly increased and micellization more thermodynamically favorable.     

Study of the Interaction Between Promazine Hydrochloride and Surfactant (Conventional/Gemini) Mixtures at Different Temperatures

In the present paper, the micellization of an amphiphilic drug, promazine hydrochloride, and gemini surfactants (16-s-16) with s = 4–6 and the monomeric hexadecyltrimethylammonium bromide (CTAB) counterparts has been examined conductometrically in the pure and mixed states in aqueous solutions at different compositions and temperatures (298.15–308.15 K). Dicationic gemini surfactants provide much better environment for the micellization behavior than the corresponding monocationic counterpart CTAB. The critical micelle concentration (cmc) values are lower than the cmc for ideal mixing, cmc ^id, suggesting attractive interactions between the two components in mixed micelles. The micellar mole fractions of surfactants, evaluated by different models, show greater contributions of surfactants in mixed micelles and increase with increasing concentrations of these surfactants. The negative values of β suggest synergism in the mixtures, which is highly beneficial as it reduces the total amount of surfactants required in a particular application, leading to reductions of cost and environmental impact. Activity coefficients (f ₁ and f ₂) are always less than unity showing nonideality in the systems. The data have been also used for evaluation of thermodynamic parameters.     

Solubilization of Magnesium Octa[(4′-Benzo-15-Crown-5)Oxy]Phthalocyaninate in Aqueous Micellar Solutions of Hexadecyltriphenylphosphonium Bromide

Electronic absorption spectroscopy and fluorimetry have been employed to study the behavior of magnesium octa[(4′-benzo-15-crown-5)oxy]phthalocyaninate (Mg[(B15C5O)₈Pc]) in aqueous micellar solutions of sodium dodecyl sulfate and hexadecyltriphenylphosphonium bromide. Conditions have been found for the existence of monomeric Mg[(B15C5O)₈Pc] complex in surfactant solutions to provide the possibility of using mixed solutions of the complex and cationic surfactants (alkyltriphenylphosphonium bromides) for photodynamic therapy. In surfactant solutions with different concentrations of micelles (c_m) and the complex (c_p), the maximum amount of monomeric Mg[(B15C5O)₈Pc] is achieved at c_m/c_p ≥ 4.     

A Thermodynamic and Physical Study on (1-Hexyl-3-methylimidazolium Chloride + 1-Pentanol and Ethylene Glycol) Binary Mixtures at Temperatures (293.15–333.15) K

Densities, ρ, viscosities, η, and refractive indices, n _D, for 1-hexyl-3-methyl imidazolium chloride ([hmim]Cl) (IL), 1-pentanol, and ethylene glycol (EG), and for the binary mixtures {x ₁[hmim]Cl + x ₂1-pentanol} and {x ₁[hmim]Cl + x ₂EG} were measured over the entire composition range at temperatures (293.15–333.15) K and ambient pressure. The excess molar volumes, \( V_{\text{m}}^{\text{E}} \), and viscosity deviations, Δη, for the binary mixtures were calculated from the experimental data. The \( V_{\text{m}}^{\text{E}} \) values of {x ₁[hmim]Cl + x ₂1-pentanol} mixtures are negative over the entire composition range at all temperatures, and increase with increasing temperature in the alcohol rich region and decrease with increasing temperature in the IL rich range. The \( V_{\text{m}}^{\text{E}} \) values of {x ₁[hmim]Cl + x ₂EG} mixture are positive in the alcohol rich range and negative in the IL rich range at all temperatures, and decrease with increasing temperature. Viscosity deviations of both mixtures are negative over the entire composition range at all temperatures and decrease with increasing temperature. The excess molar properties were correlated by Redlich–Kister equation, and the excess molar volumes were correlated using the PFP model. The fitting parameters and standard deviations were determined.     

Determination of the Water/AOT/Isooctane Reverse Micelles Size Parameters from Their Refractive Index Data

The present paper aims to study the proprieties of water confined in water/AOT/isooctane reverse micelles from their refractive indices at 298.5 K. The refractive indices of the microemulsions were investigated at increasing water concentration and at different micellar volume fractions, Φ _d. The refractive index of micellar water was deduced for a large water to AOT molar ratio, W ₀. The refractive index of interfacial water was also calculated. Then, the molar faction of interfacial water, α, was deduced for different W ₀ values and compared with those measured by NMR as reported in the literature. The results show qualitative agreement. Finally, the average aggregation number, n _agg, the area per surfactant headgroup, σ, as well as the interfacial thickness, d _i, of the reverse micelles were determined for the W ₀ values studied. The values of these structural parameters also show good qualitative agreement with NMR and small angle X-ray scattering data reported in the literature. Thus, the refractive index method can be a cheap and fast alternative for these two methods.     

Thermo Physical and Spectroscopic Properties of Binary Liquid Systems: Ethanoic Acid/Propanoic Acid/Butanoic Acid with 2-Methylaniline

Densities (ρ), speeds of sound (u), and viscosities (η) are reported for binary mixtures of 2-methylaniline with carboxylic acids (ethanoic acid, propanoic acid and butanoic acid) over the entire composition range of mole fraction at T?=?(303.15–318.15) K and at atmospheric pressure (0.1 MPa). The excess properties such as excess molar volume (V _m ^E ), excess isentropic compressibility (κ _S ^E ) and excess Gibbs energy of activation of viscous flow (G^*E) are calculated from the experimental densities, speeds of sound and viscosities. Excess properties are correlated using the Redlich–Kister polynomial equation. The partial molar volumes, \( \bar{V}_{\text{m,1}} \) and \( \bar{V}_{\text{m,2}} \), partial molar isentropic compressibilities, \( \bar{K}_{\text{s,m,1}} \) and \( \bar{K}_{\text{s,m,2}} \), excess partial molar volumes, \( \bar{V}_{\text{m,1}}^{\text{E}} \) and \( \bar{V}_{\text{m,2}}^{\text{E}} \), and excess partial molar isentropic compressibilities, \( \bar{K}_{\text{s,m,1}}^{\text{E}} \) and \( \bar{K}_{\text{s,m,2}}^{\text{E}} \), over whole composition range, partial molar volumes, \( \bar{V}_{\text{m,1}}^{ \circ } \) and \( \bar{V}_{\text{m,2}}^{ \circ } \), partial molar isentropic compressibilities, \( \bar{K}_{\text{s,m,1}}^{ \circ } \) and \( \bar{K}_{\text{s,m,2}}^{ \circ } \), excess partial molar volumes, \( \bar{V}_{\text{m,1}}^{{ \circ {\text{E}}}} \) and \( \bar{V}_{{{\text{m}},2}}^{{ \circ {\text{E}}}} \), and excess partial molar isentropic compressibilities, \( \bar{K}_{\text{s,m,1}}^{{ \circ {\text{E}}}} \) and \( \bar{K}_{\text{s,m,2}}^{{ \circ {\text{E}}}} \), of the components at infinite dilution have also been calculated from the analytically obtained Redlich–Kister polynomials. The excess molar volume V^E results are analyzed using the Prigogine–Flory–Patterson theory. Analysis of each of the three contributions viz. interactional V^E(int.), free volume V^E(fv.) and characteristic pressure p* to V^E showed that the interactional contributions are positive for all systems while the free volume and characteristic pressure p* contributions are negative for all the binary mixtures. The results are analyzed in terms of attractive forces between 2-methylaniline and carboxylic acids molecules. Good agreement is obtained between excess quantities and spectroscopic data.     

Volumetric Properties for Binary and Ternary Mixtures Containing Benzyl Alcohol,Ethyl Butyrate and Diethyl Malonate at <Emphasis Type="Italic">T</Emphasis> = (293.15–313.15) K and <Emphasis Type="Italic">p</Emphasis> = 0.087 MPa

The densities of binary and ternary mixtures of benzyl alcohol + ethyl butyrate and/or diethyl malonate were measured at T = (293.15–313.15) K and p = 0.087 MPa. From these data, the excess molar volumes, partial molar volumes, excess partial molar volumes, partial molar volumes at infinite dilution, thermal expansion coefficients and their excess values were calculated. The Redlich–Kister equations were fitted to the excess molar volumes data. The results show that the excess molar volumes for all considered binary and ternary systems are negative and decrease with increasing temperature. The same behavior was observed for the excess thermal expansion coefficients. Data for excess volumes in ternary system were fitted with the Nagata–Tamura and Cibulka models for which the Cibulka equation showed better fitting. The intermolecular interactions between molecules in these mixtures are discussed and explained based on these experimental data.