Surface Tension Method Research Articles

Specific ion effects of chloride vis-à-vis acetate, propionate and butyrate counterions on the cetylpyridinium headgroup at the micelle–solution and air–solution interfaces

Aliphatic carboxylate anions due to their varying kosmotropy and hydrophobicity are expected to compete with chloride ion for binding at interfaces. Such competition leads to the specific ion effect (SIE) and investigating the SIE at micelle/solution and air/solution interfaces has a bearing on the selectivity of ions at biological interfaces. In this paper, critical micelle concentration (cmc) values of aqueous cetylpyridinium chloride solution in the presence of acetate, propionate and butyrate anions were determined by surface tension and conductance methods. Hydrodynamic radii of the cetylpyridinium micelles were measured by using the dynamic light scattering technique. The dependence of cmc on the added salt concentration is explained in the light of the modified Corrin–Harkins (CH) equation. Non-linearity of the plots of the modified CH equation is shown to be due to exchange of carboxylate and chloride ions at the micellar interface. The surface excess values of CPC in the presence of carboxylate anions are also calculated in the light of the Gibbs adsorption isotherm. The main finding of this study is that a new method has been demonstrated for determining selectivity coefficient (it quantifies the SIE) on the basis of the modified CH equation.

Synthesis and properties of tetrasiloxane Gemini imidazolium surfactants

Two tetrasiloxane Gemini imidazolium surfactants with methylene spacer groups ([Si4-s-Si4im]Cl2, s = 4, 6) were synthesized and characterized by 1H NMR and ESI-MS spectrum. The surface activity and thermodynamic properties in aqueous solution among three categories of surfactants, including [Si4-s-Si4im]Cl2, the corresponding monomer ([Si4mim]Cl) and hydrocarbon-based Gemini imidazolium surfactant ([C14-4-C14im]Cl2), were compared by surface tension and electrical conductivity methods. A series of surface activity parameters, including cmc, γ cmc, π cmc, pc20, Γ max and A min, and the adsorption isotherms were obtained from the surface tension plots. The results indicated that the tetrasiloxane Gemini imidazolium surfactant with the longer spacer group has the higher capacity to form micelles but lower efficiency to reduce surface tension. Besides, the cmc value of [Si4-s-Si4im]Cl2 was about one order of magnitude lower than that of [Si4mim]Cl. The tetrasiloxane-based surfactants have the higher capacity to low the surface tension than the hydrocarbon-based surfactant. The adsorption isotherms of the tetrasiloxane-based surfactants are similar to those of conventional hydrocarbon-based surfactants. The thermodynamic parameters of micellization process, namely, the standard Gibbs free energy (ΔG m θ), enthalpy (ΔH m θ) and entropy (ΔS m θ) originated from the electrical conductivity measurements at five different temperatures, suggested that the micellization of [Si4-s-Si4im]Cl2 and [C14-4-C14im]Cl2 is entropy-driven process whereas aggregation of [Si4mim]Cl is enthalpy-driven process at the whole investigated temperatures. The dynamic light scattering results indicate that the aggregation size of [Si4-4-Si4im]Cl2 (113.6 nm) is larger than [Si4-6-Si4im]Cl2 (101.7 nm).

Interaction Between GMAC-m-CS and Surfactants: Surface Tension and Conductivity Methods

Glycidyl trimethyl ammonium chloride-modified chitosan (GMAC-m-CS) was synthesized through nucleophilic substitution of GMAC on CS in isopropanol dispersed system, which was characterized by FTIR and 1H NMR methods. The interaction between GMAC-m-CS and surface active ILs −1-dodecyl (tetradecyl and hexadecyl)-3-methylimidazolium bromide (CnmimBr, n = 12, 14, 16) was studied by surface tension and conductivity methods. The amount of CnmimBr adsorbed on GMAC-m-CS increases first with raising temperature, and then decreases, which reaches the largest amount at 30°C. The amount increases with the increase of alkyl chain length. The surface tension reducing capabilities of GMAC-m-CS/CnmimBr systems increase with temperature, however, decrease with the increase of GMAC-m-CS concentration. The aggregation processes of C14mimBr in solutions without GMAC-m-CS and with high concentration of GMAC-m-CS were entropy driven; however, it is enthalpy driven in solutions with low concentration of GMAC-m-CS. Based on the analysis of properties of GMAC-m-CS/CnmimBr, the interaction model of GMAC-m-CS/ILs was proposed.

The clouding phenomena of mixed surfactant (non-ionic Triton X-114 + cationic gemini 16-5-16) solutions: Influence of inorganic and organic additives on the cloud point

In this investigation, we have studied the micellization of non-ionic surfactant, Triton X-114 (by surface tension measurement) and cationic gemini surfactant, pentanediyl-1,5-bis(dimethylcetylammonium bromide) (16-5-16) by surface tension, conductivity and dye solubilization methods and the clouding phenomena of mixed surfactant (non-ionic Triton X-114+cationic gemini 16-5-16) system in aqueous solution. The critical micelle concentration (CMC) of Triton X-114 and 16-5-16 were measured and their surface properties and thermodynamics were evaluated. In aqueous solution, non-ionic surfactant, Triton X-114 undergoes phase separation or cloud point (CP). Herein, we also report the influence of additives (e.g., electrolytes, sugars, amino acids, etc.) on the CP of Triton X-114 in aqueous solutions. The CP showed a concentration dependent variation in the absence of any added compound (additives). With the addition of additives, the CP values were found to decrease and increase. It is found that the CP of pure Triton X-114 is concentration dependent; and the presence of gemini surfactant (16-5-16) increases the CP. However, all additives in the presence of the gemini surfactant (i.e., Triton X-114+16-5-16 system) decrease the CP. The results are discussed by taking into consideration the nature of the additives. The thermodynamic parameters are also evaluated at CP.

Micelle assisted synthesis of La2O3 nanoparticles and their applications in photodegradation of bromophenol blue

Lanthanum Oxide (La2O3) nanoparticles were synthesized by precipitation method using alkylbenzyl dimethyl ammonium chloride (Benzalkonium chloride) surfactant. The critical micelle concentration (CMC) value of the surfactant was determined using conductance and surface tension methods. The nanoparticles were characterized using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD) analysis. Crystallite size and geometry of La2O3 nanoparticles, established through XRD, are 40 nm and hexagonal, respectively. The optical property was calculated using solid phase UV-visible absorption spectrophotometer with band gap of 4.2 eV. Photocatalytic efficiency of La2O3 nanoparticles was studied against bromophenolblue (organic pollutant) with and without UV radiations. Percentage degradation and first order rate constant values were determined as 24.7% and 0.0942 min–1 without irradiation and that they were 50.4 % and 0.0941 min-1with irradiation, respectively.

Investigation of structural parameters and self-aggregation of Algerian asphaltenes in organic solvents

Elemental analysis, Fourier transform infrared (FTIR), 1H-NMR, fluorescence spectroscopy, and surface tension methods have been used to characterize the molecular structure and the aggregation behaviors of two asphaltenic fractions derived, respectively, from an Algerian petroleum well and a corresponding storage tank deposit. Elemental analysis, FTIR, 1H-NMR, and fluorescence spectroscopy were used to investigate the chemical composition and structural parameters of asphaltenes, while the surface tension method was used to measure the critical micelle concentration (CMC) in organic solvents with different solubility parameters and polarities in order to characterize the asphaltenes’ aggregation behaviors. Results show that the unstable asphaltenes fraction extracted from the storage tank deposit possesses a higher polarity (higher heteroatoms content) and a lower aromaticity than stable asphaltenes from the petroleum well. The CMC results indicate that asphaltenes with high polarity and low aromaticity have a high solubility in polar solvents such as nitrobenzene, whereas asphaltenes with low polarity and high aromaticity are more soluble in solvents with weak polarity, like toluene. It is concluded that the difference of structure of asphaltene samples and polarity of solvents can lead to difference of aggregation behaviors.

The effect of salts on micellization in C12mimBr/Triton X-100 aqueous mixtures and on the surface properties of the solutions

Herein, we report our studies on the mixed aqueous solutions of 1-dodecyl-3-methylimidazolium bromide (C12mimBr) and Triton X-100 in the presence of sodium bromide and sodium chloride by surface tension and conductivity measurement methods. The critical micelle concentration and several other parameters such as maximum surface excess, minimum area per molecule and surface pressure at the CMC were calculated from the data of surface tension investigation. The critical micelle concentration values decreased with the increase of salt concentration. Rubingh’s theory was applied to calculate the mole fraction (X 1) of C12mimBr in the mixed systems. The results showed that X 1 increased most significantly with the concentration of the salt in the presence of NaBr. The values of standard Gibbs energies of micellization and interfacial adsorption have also been calculated; both were found to be negative for all systems, indicating the spontaneity of micellization and adsorption of the surfactants.

Effect of pyrrolidinium based ionic liquid on the channel form of gramicidin in lipid vesicles

The present work is focused on the interaction between membrane bound gramicidin and 1-butyl-1-methyl-2-oxopyrrolidinium bromide (BMOP) ionic liquid. Ionic liquids (ILs) are solvents that are often liquid at room temperature and composed of organic cation and appropriate anion. The gramicidin peptide forms prototypical ion channels for cations, which have been extensively used to study the organization, dynamics, and function of membrane spanning channels. The interaction was studied by circular dichroism, steady state, time-resolved fluorescence spectroscopy in combination with dynamic surface tension and field emission scanning electron microscopic methods (FESEM). The results obtained from circular dichroism shows that the BMOP interacts with the channel form of gramicidin in lipid vesicle without any considerable effect on its conformation. The Red-edge excitation shift (REES) also supported the above findings. In addition, the fluorescence studies suggested that BMOP makes ground state complex with ion channel, which was further supported by time resolved measurements. Furthermore, dynamic surface tension analysis shows the faster adsorption of BMOP with membrane bound gramicidin at the air–water interface. Additionally, FESEM results indicated that BMOP forms a film around the membrane bound gramicidin at higher concentration. These results are potentially useful to analyze the effect of ionic liquids on the behaviour of membrane proteins.

Dodecenylsuccinic anhydride derivatives of gum karaya (Sterculia urens): preparation, characterization, and their antibacterial properties.

Esterifications of the tree-based gum, gum karaya (GK), using dodecenylsuccinic anhydride (DDSA) were carried out in aqueous solutions. GK was deacetylated using alkali treatment to obtain deacetylated gum karaya (DGK). The DGK and its DDSA derivative were characterized using gel permeation chromatography/multiangle laser light scattering (GPC/MALLS), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), proton nuclear magnetic resonance spectroscopy ((1)H NMR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) analysis, and rheological studies. The degree of substitution was found to be 10.25% for DGK using (1)H NMR spectroscopy. The critical aggregation concentration of DDSA-DGK was determined using dye solubilization and surface tension methods. The antibacterial activity of the DDSA-DGK derivative was then investigated against Gram-negative Escherichia coli and Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus. The DDSA-DGK derivative has the potential for use as a stabilizing agent in food and nonfood applications. It can also be developed as an antibacterial agent.

Aggregation behavior of derivatives of sodium alginate and N-octyl-β-d-glucopyranoside in aqueous solutions

Abstract In this study, the aggregation of N-octyl-β- d -glucopyranoside (OGP) and cholesteryl grafted sodium alginate derivative (CSAD) in solutions was investigated by surface tension method, fluorescence spectroscopy, dynamic light scattering, and transmission electron microscopy. Results showed that cholesteryl of CSAD and OGP were adsorbed competitively to the gas–solution interface. Four different conformations of complexes were found with the increasing of OGP concentration (C). When C 2 ), the quantity of pearl-chain structure complexes increases, they interact to form core–shell structure complexes, and several core–shell structure complexes formed short string-structures by association of CSAD molecule. When C > C 2 , adsorption amount of OGP to CSAD reached saturation, OGP molecules formed small single OGP micelles, while the string-structures were dissolved because the cholesteryl among the micelles were replaced by the single OGP micelles.

Counter ion binding in solutions of sodium dodecylsulfate in water–ethylene glycol mixtures and the Corrin–Harkins equation

The aggregation behavior of sodium dodecylsulfate (SDS) in mixtures of water and ethylene glycol (EG) in the presence of varying amounts of sodium chloride has been studied by using surface tension, conductance and fluorescence methods. The critical micelle concentration (cmc) values obtained from the different methods are found to be comparable. The cmc value of SDS keeps on increasing with increase in concentration of EG due to the decrease in the solvophobicity of the surfactant, and it decreases with increase in the salt concentration due to reduction in the repulsive interaction between the head groups. The counter ion binding behavior of SDS in the mixed solvent is assessed by using the Corrin–Harkins (CH) equation. The applicability of the CH equation appears to be limited in the mixed solvent as deviation from this equation has been observed in the region of low concentration of NaCl when the EG amount becomes equal to or more than 50 w/w %. It is observed that this particular deviation from the CH plot occurs in the region where the total counter ion concentration at the cmc is controlled by the ionic surfactant.

A direct comparison of the interaction of bovine serum albumin and gelatin with sodium deoxycholate in aqueous solutions

Surface tension, fluorescence and circular dichroism (CD) methods have been used to investigate the interaction between a biological surfactant sodium deoxycholate (NaDC) and proteins including bovine serum albumin (BSA) and gelatin. It can be seen from the surface tension measurements that both NaDC/BSA and NaDC/gelatin systems can form complexes and the ability of NaDC/BSA to lower surface tension is more obvious than that of NaDC/gelatin. The formation of the complexes influences not only the polarity of the microenvironment of the systems but also their fluorescence spectra. The far-UV CD spectra shows that the α-helical network of BSA increases first and then decreases as the concentration of NaDC increases, while the random coil content of gelatin always increases. A model of interaction between protein and NaDC influenced by the concentration of NaDC has been brought out based on the data gained from this study.

Interaction Between EPTAC-Modified Gelatin and Surfactants: Surface Tension and Conductivity Methods

Gelatin, one of the most valuable macromolecules and by-products of the leather industry, was modified by the addition of 2,3-epoxypropyl trimethyl ammonium chloride (EPTAC). The interaction between EPTAC-modified gelatin (EPTAC-gelatin) and cetyltrimethyl ammonium bromide (CTAB) or sodium dodecyl benzene sulfonate (SDBS) was studied by surface tension and conductivity methods. We found that EPTAC-gelatin adsorbed more CTAB than SDBS but the surface-tension-reducing capabilities of EPTAC-gelatin–CTAB and EPTAC-gelatin–SDBS were almost equal. The micellization process of CTAB was enthalpy-driven but that of SDBS was entropy-driven at low concentrations of EPTAC-gelatin and enthalpy-driven at high concentrations. Based on the analysis of EPTAC-gelatin–CTAB (SDBS) solution properties, interaction models of EPTAC-gelatin–CTAB (SDBS) were proposed.

0112 局所の表面張力を考慮した振動板上の微小液滴形状の解析

Dynamic surface tension is one of the most important physical properties for interfacial phenomena of many applications. A proposal on the measurement method of dynamic surface tension was found in previous research, which uses local deformations in the droplet surface. To clarify the local flow in the tiny droplet, we investigated the deformation of shell liquid of the droplet on the vibrating plate using 2D finite element method. The gas-liquid droplet surface area was calculated locally in each section of radial angle under given apparent gravity. We found that the interface of the local droplet deformation can be related to the local surface tension.

Synthesis, surface activity and aggregation behavior of Gemini imidazolium surfactants 1,3-bis(3-alkylimidazolium-1-yl) propane bromide

Abstract A novel class of Gemini imidazolium surfactants 1,3-bis(3-alkylimidazolium-1-yl) propane bromide [C n -3-C n im]Br 2 ( n = 8, 10, 12) were synthesized and characterized by FT-IR, 1 H NMR and elemental analysis. The surface activity and aggregation behavior of [C n -3-C n im]Br 2 ( n = 8, 10, 12) were investigated by surface tension, conductivity and steady fluorescence methods. A series of surface active parameters, including cmc, Γ max , p C 20 , cmc/ C 20 , A min , γ cmc and Π cmc were obtained from surface tension measurement. It was indicated that Gemini imidazolium surfactants with the longer alkyl chain showed the higher surface activity. The thermodynamic parameters of micellization process, namely, standard Gibbs free energy (Δ G m ο ), enthalpy (Δ H m ο ) and entropy (Δ S m ο ) were derived from conductivity measurement at different temperatures. The micropolarity and the mean aggregation number ( N agg ) of micelles were evaluated from steady fluorescence spectra. The results revealed that the micropolarity and N agg of micelles decreased with the increase of hydrocarbon chain length.

Binding of phenol red to cetylpyridinium chloride at air–solution and micelle–solution interfaces in aqueous ethylene glycol media

Knowledge about the fundamental aspects of dye–surfactant interactions is important for developing better formulations required in textile and other coloring industries, and also for improving the efficacy of dye separation processes. In this paper, the interaction between cetylpyridinium chloride (CPC) surfactant and phenol red (PR) dye has been investigated in water and water+ethylene glycol (EG) media using surface tension and spectrophotometric methods. The synergetic effect of PR on the surface tension reducing ability of CPC decreases on adding EG. The modified Corrin–Harkins equation has been derived using the Gibbs–Duhem approach, and by applying this equation CP (cetylpyridinium) micelles are found to be bound predominantly by PR− which is shown to be in accordance with the Collins’ ion-specificity rule. From the absorbance data, using an equation that accounts for the stoichiometry of dye–micelle interaction, the values of binding constant were determined and in water+EG media the electrostatic interactions are found to control the binding of PR− to CP micelles. A spectrophotometric method to determine the counterion binding constant is illustrated. A simple expression that can predict the value of the binding constant of dye–micelle interaction at the cmc is proposed. Dynamic light scattering measurements showed that the amount of dye required to increase the micellar size is dependent on the solvophobicity of the medium. Surface excess values indicate that at the air–solution interface the monolayer consists of both CP+ and PR− when the medium is water, whereas in water+EG the monolayer has CP+ alone and PR− resides in the subsurface.

Effect of Head Groups, Temperature, and Polymer Concentration on Surfactant—Polymer Interactions

AbstractThe micellization behaviour of sodium dodecyl sulphate, sodium dodecylbenzenesulfonate, hexadecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, and cetylpyridinium chloride in water and in aqueous solutions of polyethylene oxide (PEO, molecular weight = 100,000) having concentrations (0.005–0.04 %, w/v) has been studied at different temperatures (288.15–318.15 K) using conductivity, surface tension, and viscosity methods. From conductivity measurements various micellar parameters, like critical micellar concentration (CMC), critical aggregation concentration (CAC), polymer saturation point (PSP), degree of ionization (β), and standard free energy of transfer (), have been calculated. CAC values have been found to decrease with polymer concentration and increase with temperature. However, the PSP values increase with both polymer concentration and temperature for all surfactants. Similar parameters have also been calculated from surface tension data (CMCσ, CACσ, PSPσ) along with other parameters such as maximum surface excess concentration at the air/water interface (), minimum area per molecule (Amin), and packing parameter (p). The CMCσ, CACσ, and PSPσ values are smaller than the corresponding CMC, CAC, and PSP values, but both show similar behaviour with temperature and concentration of polymer. Various parameters indicate that the presence of the aromatic ring in the head group of surfactant decreases its interaction with PEO, whereas the increased hydrophobicity in the tail leads to stronger interactions with PEO. Viscosity studies further supplement the conclusions drawn from the above results.

Interaction between biosurfactant surfactin and cationic surfactant cetyl trimethyl ammonium bromide in mixed micelle

An anionic/cationic mixed surfactant aqueous system of surfactin and cetyl trimethyl ammonium bromide (CTAB) at different molar ratios was studied by surface tension and fluorescence methods (pH 8.0). Various parameters that included critical micelle concentration (cmc), micellar composition (X 1), and interaction parameter (β m) as well as thermodynamic properties of mixed micelles were determined. The β m was found to be negative and the mixed system was found to have much lower cmc than pure surfactant systems. There exits synergism between anionic surfactin and cationic CTAB surfactants. The degree of participation of surfactin in the formation of mixed micelle changes with mixing ratio of the two surfactants. The results of aggregation number, fluorescence anisotropy, and viscosity indicate that more packed and larger aggregates were formed from mixed surfactants than unmixed, and the mixed system may be able to form vesicle spontaneously at high molar fraction of surfactin.

Self-assembly phenomena of the brush-like amphiphilic organopolysiloxanes in aqueous solution

A series of brush-like amphiphilic organopolysiloxanes with varying hydrophilic side-chains was prepared, and the assembly behavior of these promising polymers was investigated in aqueous solution using a combination method of surface tension, steady-state fluorescence, dynamic light scattering, and transmission electron microscopy. An increasing number of side-chains could lead a higher surface tension of the polymer solution. The polymers formed regular “micelle-like” spherical multipolymer assemblies in aqueous solution with the size distributed from the scale of hundreds to that of tens of nanometer, and the polymers that possessed more of the side-chains would form comparatively loose and swollen assemblies with slightly higher micropolarities and bigger dimensions. The interesting discovery in this report was that the visible clearness of the solution could be improved by increasing the hydrophilicity of the assemblies in the solution. Copyright © 2014 John Wiley & Sons, Ltd.

Synthesis and Surface Properties of Novel Gemini Imidazolium Surfactants

AbstractFive new Gemini imidazolium surfactants were synthesized from imidazole and 1‐bromoalkane (C8, C10, C12, C14, C16) to get 1‐alkylimidazole, which was further reacted with 1,3‐dichloropropan‐2‐ol to form the surfactant molecule, 1,1′‐(propane‐1,3‐diyl‐2‐ol) bis(3‐alkyl‐1H‐imidazol‐3‐ium) chloride. The structures of the five new surfactants and intermediates were characterized by 1H‐NMR, 13C‐NMR and IR spectra. Thermal properties of the five new surfactants were studied with thermogravimetric analysis and differential scanning calorimetry, the five new surfactants showed a transition from a crystalline phase to a thermotropic liquid–crystalline phase at around ca. 100 °C, which transformed to an isotropic liquid phase at around ca. 165 °C. The five new surfactants critical micelle concentrations (CMC) in the aqueous solutions were determined by surface tension and electrical conductivity methods. The surface tension measurements provided a series of parameters, including critical micelle concentration (CMC), surface tension at the CMC (γCMC), adsorption efficiency (pC20), and effectiveness of surface tension reduction (πCMC). In addition, with application of the Gibbs adsorption isotherm, maximum surface excess concentration (Γmax) and minimum surface area/molecule (Amin) at the air–water interface were obtained. The parameters β (degree of counterion binding to micelles), ΔGadsθ (Gibbs free energy of adsorption), and ΔGmicθ (Gibbs free energy change of micellization) were also derived. The results indicated that the five new Gemini surfactants exhibited very low CMC and a good efficiency in lowering the surface tension of water. The foamability and foam stability of the five new surfactants were also examined at different CMC.