Surface Tension Method Research Articles

Application of the Ferguson principle to the antibacterial activity of mono- and multi-component solutions of quaternary ammonium surface-active agents.

Abstract Critical micelle concentrations (cmc) have been measured by the surface tension method for binary mixtures of dodecyltrimethyl-ammonium bromide with tetradecyltrimethylammonium bromide, binary mixtures of C14/C16 homologues, a ternary mixture of the C12/C14/C16 compounds and additionally for each component individually. The antibacterial activities of the systems against Escherichia coli were determined by a British Standard Method (B.S. 3286: 1960). Thermodynamic activities of the solutions at two survivor levels, calculated from the physical and biological measurements, were sufficiently constant to sustain the Ferguson principle for these micelle-forming antibacterial agents. A theoretical treatment of micelle formation for multi-component solutions of surfactants gave cmc’s by calculation in close agreement with the experimentally determined values. The purity and composition of the surfactants was determined by gas liquid chromatography.

Enthalpy–entropy compensation of ionic liquid-type Gemini imidazolium surfactants in aqueous solutions: A free energy perturbation study

Molecular dynamics simulations and free energy perturbation (FEP) were performed for studying the enthalpy–entropy compensation with a series of ionic liquid-type Gemini imidazolium surfactants (ILGIS), with different carbon atoms of the hydrophobic group or the spacer chain length, in aqueous solutions. According to the law of mass action, the thermodynamic properties of micellization in aqueous solutions for ILGIS were discussed. The results show that the solvation free energy changes calculated from the free energy perturbation are close to the Gibbs free energy calculated from the surface tension method and can be used to discriminate the tendency for micellization and predict the thermodynamic properties of ILGIS. The micellization of ILGIS in aqueous solutions is a spontaneous and entropy-driven process. It is enthalpy–entropy compensated, and the enthalpy–entropy compensation plots exhibit an excellent linearity. The compensation temperature was found to be (307 ± 2) K. As the number carbon atoms in the alkyl chains is increased, the tendency and stability of micellization both increase. At spacer length S ⩽ 6, with the spacer chain length increasing, the thermodynamic favorability and stability of the micelles decrease. However, if S > 6, thermodynamic favorability and stability increase with raising the spacer chain length.

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

AbstractInterfacial 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.

The thermodynamic properties of solutions of L-ascorbic acid in dimethyl sulfoxide and water-dimethyl sulfoxide mixtures

Solutions of L-ascorbic acid (AA) in dimethyl sulfoxide (DMSO) and DMSO-water mixtures were studied by the densitometry, surface tension, and calorimetry methods. The apparent and partial molar volumes of AA in solutions at 298.15 K were calculated. Surface tension insignificantly increased as the concentration of AA in DMSO grew. The enthalpies of solution of AA in the solvents and the enthalpies of transfer of AA from water into DMSO and DMSO-water mixed solvents were calculated. The results obtained were explained by the existence of H-bonds between AA and DMSO molecules.

Effect of sodium salicylate, sodium oxalate, and sodium chloride on the micellization and adsorption of sodium deoxycholate in aqueous solutions

The salicylate ion increases the rate of bile flow (choleretic effect) and bile salts are known to affect the colonic absorption of oxalate. Owing to this physiological relevance of salicylate and oxalate ions, critical micelle concentration (cmc) values of sodium deoxycholate (NaDC) were determined in aqueous sodium oxalate, sodium salicylate, and sodium chloride solutions by using surface tension, fluorescence, and EMF methods. The results indicate, besides a counterion effect, the influence of coanions on the cmc. In the range from 25 to 40°C, cmc increases almost linearly with temperature. In the temperature range from 30 to 40°C, the counterion binding constant β of NaDC micelles has the same value (0.17±0.01) in the presence of sodium chloride and sodium salicylate. On the other hand, in sodium oxalate solution β=0.05±0.02 when oxalate concentration is less than or equal to c* and β=0.48±0.04 above c*, where c*≈0.038molkg−1. EMF measurements also supported this type of counterion binding to NaDC micelles in sodium oxalate solutions. In sodium oxalate solution, at c* a change in the shape of deoxycholate micelles is expected to take place. Salicylate, oxalate, and chloride coanions have a similar effect on the adsorption of NaDC. This study reveals that the choleretic effect of salicylate is not due to the influence of salicylate ions on the micellization of NaDC.

Oscillations of weakly viscous conducting liquid drops in a strong magnetic field

We analyse small-amplitude oscillations of a weakly viscous electrically conducting liquid drop in a strong uniform DC magnetic field. An asymptotic solution is obtained showing that the magnetic field does not affect the shape eigenmodes, which remain the spherical harmonics as in the non-magnetic case. A strong magnetic field, however, constrains the liquid flow associated with the oscillations and, thus, reduces the oscillation frequencies by increasing effective inertia of the liquid. In such a field, liquid oscillates in a two-dimensional (2D) way as solid columns aligned with the field. Two types of oscillations are possible: longitudinal and transversal to the field. Such oscillations are weakly damped by a strong magnetic field – the stronger the field, the weaker the damping, except for the axisymmetric transversal and inherently 2D modes. The former are overdamped because of being incompatible with the incompressibility constraint, whereas the latter are not affected at all because of being naturally invariant along the field. Since the magnetic damping for all other modes decreases inversely with the square of the field strength, viscous damping may become important in a sufficiently strong magnetic field. The viscous damping is found analytically by a simple energy dissipation approach which is shown for the longitudinal modes to be equivalent to a much more complicated eigenvalue perturbation technique. This study provides a theoretical basis for the development of new measurement methods of surface tension, viscosity and the electrical conductivity of liquid metals using the oscillating drop technique in a strong superimposed DC magnetic field.

Thermophysical Properties of Undercooled Alloys: An Overview of the Molecular Simulation Approaches

We review the studies on the thermophysical properties of undercooled metals and alloys by molecular simulations in recent years. The simulation methods of melting temperature, enthalpy, specific heat, surface tension, diffusion coefficient and viscosity are introduced and the simulated results are summarized. By comparing the experimental results and various theoretical models, the temperature and the composition dependences of the thermophysical properties in undercooled regime are discussed.

Aqueous Solution Properties of Disulfide-Linked Fluorinated Gemini and Cleaved Monomeric Thiol Surfactants

We prepared a fluorinated gemini surfactant containing a disulfide bond in its spacer chain, [C₈F₁₇(CH₂)₃N(CH₃)₂CH₂CH₂SSCH₂CH₂N(CH₃)₂(CH₂)₃C₈F₁₇]2Cl, and its analogue with a hexamethylene spacer. Monomeric thiol surfactant, [C₈F₁₇(CH₂)₃N(CH₃)₂CH₂CH₂SH]Cl, was readily produced by the cleavage of the gemini surfactant using dithiothreitol in water. The critical micelle concentration was determined using surface tension, conductivity, and fluorescence probe methods. The critical micelle concentration of the monomeric surfactant was significantly larger than that of the gemini surfactant. The surface tension of aqueous solution for the cleaved monomeric thiol surfactant returned gradually to the original value through the formation of the disulfide bond via air oxidation.

Effect of Oxyethylete Units on Adsorption and Micellization Properties of Novel Benzene Sulfonate Surfactants

The surface tension and fluorescence spectra of sodium octyl-[ω-octyloxy-poly(oxyethylene)]-yl-benzene sulfonates (APEnBS) aqueous solutions have been investigated by Wilhelmy plate method and intrinsic probe methods, respectively to study the effect of EO units on their properties. It was discovered that the surface performance of these surfactants was greatly outstanding: the values of critical micelle concentration (CMC) reached to be of the order of magnitude of 10−5 mol/L, the values of surface tension at CMC, γCMC, were between 25.79 to 31.02 mN/m, and the effectiveness and efficiency of surface tension reduction were excellent. The introduction of oxyethylene units to the surfactant molecule evidently improved the solubility of APEnBS. With the increase in EO units, the CMC slightly changed after the first decreased. On the other hand, the surface excess concentration at saturation, Γ max, decreased after the first increased and γCMC increased after the first decreased accordingly. The CMC determined by fluorescence spectra of intrinsic probe method were accorded with the CMC measured by surface tension method. The aggregation number N, characterized by quenching the fluorescence spectra with methyl viologen (MV2+) as the extrinsic quencher, gradually decreased first (from 0 to1) and then slightly changed (from 1 to 4) with increasing EO chain length. So we concluded that the appropriate number of EO units was the key factor to get the best physicochemical properties of APEnBS.

Application of the UNIFAC model for prediction of surface tension and thickness of the surface layer in the binary mixtures

Surface properties of binary mixtures of (alkanol with acetonitrile) have been measured by surface tension method at T = 298.15 K and atmospheric pressure. The UNIFAC method is used for calculation activity coefficients of surface and bulk phases. Also, the surface tension has been predicted based on the Suarez method. This method combines a model for the description of surface tension of liquid mixtures with a UNIFAC group contribution method for the calculation of activity coefficient. Two techniques for calculation of molar surface areas, based on Paquette areas and Rasmussen areas are tested. On comparing the computed values of surface tension by the present approaches with experimental data, satisfactory results have been observed. In addition, the relative Gibbs adsorption and the surface mole fraction have been evaluated using this model. It is possible to calculate the thickness of liquid–vapor interfaces starting from surface tension data. A novel procedure is developed to obtain the thickness of liquid–vapor interfaces as a function of composition in binary systems.

Synthesis and micellization of polydimethylsiloxane– carboxy-terminated poly(ethylene oxide) graft copolymer in aqueous and organic media and its application for the synthesis of core-shell magnetite particles

AbstractAn amphiphilic graft copolymer having an average of 7-8 carboxyesterterminated poly(ethylene oxide) grafted sequences on each polydimethylsiloxane main chain was obtained by a multistep procedure. Through fluorescence, surface tension and laser diffractometry methods the graft copolymer was proved to undergo micellization in aqueous media. In water, the critical micellization concentrations (CMC) are dependent on pH. Two CMC values were established for pH = 4, i.e. CMC1 = 1.01 g/L and CMC2 = 1.73 g/L corresponding to the transition from single chain to multiple chain micelles and to intermicellar aggregation, respectively. Between CMC1 and CMC2, the dimensions of micelles increased from 18 nm to 46 nm. The graft copolymer was proved to efficiently act as surfactant in the preparation of magnetite particles with a hydrophobic siloxane shell.

Interactions between gemini and nonionic pharmaceutical surfactants

The nature and strength of the interactions between the 1,3-bis(dimethylhexadecyl)propanediammonium dibromide (16-3-16) gemini surfactant and a homologous series of nonionic polyoxyethylene (20) sorbitan ester surfactants having laurate (Tween 20), stearate (Tween 60), or oleate (Tween 80) alkyl tails has been investigated. The critical micelle concentration (cmc) values of the mixed gemini–tween systems were determined using the du Noüy ring surface tension method, and the results have been analyzed using Clint’s, Rubingh’s, Motomura’s, and Maeda’s theories for mixed micellar systems. The results demonstrate a synergistic mixing behaviour between the Tween surfactants and the 16-3-16 gemini surfactant, where the strength of interaction is dependent upon the chain length and saturation of the Tween alkyl tail.

Interactions of Polyglycol Ethers with Anionic Surfactants in Water

In order to determine the thermodynamic properties of the aggregation process between sodiun dodecyl sulfate (SDS) and polyglycol ethers (PEG) with average molar mass 35000, 20000, and 10000, the temperature dependence of polymer-surfactant ınteraction is used. Surface tension, ionic conductivity, and solubilization methods have been used to quantify the interactions.It was found that the transfer of SDS micelles from aqueous media to aqueous polymer media is more feasible than the reverse. In addition, the hydropholic interaction seems to be important, as opposed to the charge-nonpolar type interaction.

Effect of Salt on the Adsorption Affinity of an Aromatic Carbonyl Molecule to the Air−Aqueous Interface: Insight for Aqueous Environmental Interfaces

The interface-selective second harmonic generation (SHG) nonlinear optical spectroscopy and the surface tension method have been used to measure the effect of electrolyte on the adsorption isotherm of 4-hydroxyacetophenone (4-HA) at the air−solution interface. It was observed that high NaCl concentration favors adsorption of organic molecules to the air−solution interface. Measurements of the polarization of the SHG field showed that the orientation of the organic molecule at the air−solution interface is close to that in the neat air−water interface and does not vary with organic concentration. The free energy of adsorption of the molecule to the air−solution interface becomes significantly more negative with an increase in salt concentration, and good agreement was found between the results from the two different techniques. We conclude that the increased affinity of 4-HA for the air−water interface in the presence of NaCl is due to the salting-out effect.

Synthesis and Surface Property of Cashew-based Surfactants

Cashew phenol polyoxyethylene ethers ( CPE) were synthesized from cashew phenol as raw materials. In the presence of sodium hydroxide as a catalyst,a series of cashew phenol polyoxyethylene ether carboxylates( CPEC) were synthesized with CPE and chloroacetic acid. The products were structurally confirmed by FT-IR and elemental analysis. Surface properties were determined by a surface tension method. The experimental results showed that when critical micelle concentrations( CMC) of the surfactants were 9. 30,8. 50,8. 10 and 7. 71 mmol/L,the corresponding surface tensions at CMC were 28. 38,28. 60,30. 40 and 30. 00 mN/m,respectively. By means of Gibbs formula,the maximum adsorption amounts of the surfactants were 0. 7087,0. 7350,0. 7195 and 0. 7346 μmol/m2,and the minimal molecular projective areas of them were 2. 3439,2. 2600,2. 3087 and 2. 2613 nm2,respectively,on solution surface.

Study on the Synthesis and Surface Activities of Novel Alkyl Sulfonate Gemini Surfactants

Abstract Three novel dialkyl disulfonate gemini surfactants (Cn-6-Cn, n = 6, 8, 12; n is carbon number of hydrophobic chain) were synthesized from cyanuric chloride, aliphatic amine and taurine. The chemical structures of the prepared compounds were confirmed by 1H NMR, 13C NMR, IR spectra and ESI-MS. Their critical micelle concentrations (CMC) in the aqueous solutions at 25°C were determined by surface-tension method. With the increasing length of the hydrophobic carbon chain, the values of their CMC decreased. The surface tension measurements of Cn-6-Cn give low CMC, great efficiency in lowering the surface tension, and strong adsorption at air–water interface. In addition, adsorption and micellization behavior of Cn-6-Cn were estimated by the parameter of pC20, the minimum average area per surfactant molecule (Amin).

Comparative Study on the Effect of NaBr on the Interaction Between Alkyltrimethylammonium Bromide and β-Cyclodextrin

The effect of NaBr on the interaction between alkyltrimethylammonium bromide (CnTAB (n = 14 for TTAB and 16 for CTAB)) and ß-CD was studied by surface tension method. The first decrease in the γcmc of TTAB/ß-CD in the presence of NaBr mainly due to the elongated effective chain length of the hydrophobic part of the TTAB/ß-CD complexes; while the increase in the γcmc of both of the TTAB/ß-CD and CTAB/ß-CD in the presence of NaBr could be attributed to the close pack of CnTAB at the air/water interface.

Synthesis, Characterization and Surface Properties of Series Sulfobetaine Surfactants

AbstractA series of surface active sulfo‐propane betaines and sulfo‐butane betaines were synthesized with high yields by the reaction of an appropriate N,N‐dimethyl alkylamine with an excess of 1,3‐propane sultone and 1,4‐butane sultone. The structures were characterized by 1H‐NMR spectroscopy and elemental analysis. The micellar properties of these compounds were determined by surface tension methods. Surface tension measurements also provide information about the dependence of the surface tension at the CMC (γcmc), pC20 (negative logarithm of the surfactant molar concentration C20 required to reduce the surface tension by 20 mN/m), the surface excess (Γmax) at air/solution interface, the minimum area per surfactant molecule at the air solution interface (A).

Conductometry and Thermodynamics Study of Metal Dioctylsulfosuccinate in Aqueous Solution

The aggregation behavior of metal dioctylsulfosuccinate (MDSS) [Na+, Mg2+, Mn2+, Co2+, and Ni2+] in water has been studied by electrical conductivity (at 303.15 to 323.15 K) and surface tension method (at 303.15 K). Critical micelle concentration (CMCs), degree of counterion dissociation (β) evaluated from conductivity data. Using law of mass action, the thermodynamic parameters viz. Gibbs function (), enthalpy (), and entropy () were evaluated. The enthalpy of micellization decreases strongly with increasing temperature. ΔG is always negative (thermodynamically favored process), and slightly temperature and counterion dependent. Gibbs energy and entropy exploit micellization as thermodynamic favorable process. The electrostatic repulsions between ionic head groups, which prevent the aggregation, are progressively screened as the ionic character decreases with the size of counterion. The plots of differential conductivity (dk/dc) T,P , versus the total surfactant concentration enables us to determine the CMC values more precisely than the conventional method. The data are explained in terms of molecular characteristics of surfactants viz. degree of dissociation, polar head group size and counerion.

Synthesis and Properties of Novel Alkyl Sulfonate Gemini Surfactants

AbstractA series of novel dialkyl disulfonate gemini surfactants (2Cn‐SCT where n is the carbon number of the hydrophobic chain) were synthesized from cyanuric chloride, aliphatic amine and taurine. The chemical structures of the prepared compounds were confirmed by 1H NMR, 13C NMR, IR spectra, and ESI–MS. Their critical micelle concentrations (CMC) in the aqueous solutions at 25 °C were determined by surface tension and electrical conductivity methods. With the increasing length of the carbon chain, the values of their CMC initially decreased, and then increased with an alkyl chain length of 14. The surface tension measurements of 2Cn‐SCT (except for n = 14) determined that there is a low CMC, a great efficiency in lowering the surface tension, and a strong adsorption at the air–water interface. In addition, adsorption and micellization behavior of 2Cn‐SCT were estimated from pC20, the minimum average area per surfactant molecule (Amin), and standard free energy micellization and adsorption (). These properties are significantly influenced by the chain length n, and the adsorption is promoted more than the micellization.