Degree Of Counterion Dissociation Research Articles

Effect of polar organic solvents on the surface adsorption and micelle formation of surface active ionic liquid 1-dodecyl-3-methylimidazolium bromide in aqueous solutions and comparison with the traditional cationic surfactant dodecyltrimethylammonium bromide

The effects of polar organic solvents methanol, ethanol, n-propanol, n-butanol, ethylene glycol and propylene glycol on the micellization and surface adsorption behavior of surface active ionic liquid (SAIL) 1-dodecyl-3-methylimidazolium bromide (DDMIm-Br) and traditional cationic surfactant dodecyltrimethylammonium bromide (DTAB) have been studied by experimentally measured electrical conductivities and surface tensions. The main focus was on the effect of added organic solvents on the critical micelle concentration (cmc), degree of counterion dissociation on the micelles (α), surface tension at the cmc (γcmc), adsorption efficiency (pC20), effectiveness of surface tension reduction (Πcmc), the maximum surface excess concentration (Γmax), minimum surface area per molecule (Amin) at interface of air/solution and standard Gibbs free energy of micellization (ΔGm∘) of both the investigated surfactants in aqueous solutions. The results show that methanol, ethanol, ethylene glycol and propylene glycol act as a cosolvent and slightly increase the cmc of both surfactants in aqueous solutions. However the more hydrophobic solvents n-propanol and n-butanol, act as a cosurfactant and decrease the cmc by their presence. The accepted correlations were found between the different interfacial properties and the relative permittivity of the added organic solvents. As the difference between the relative permittivity of added organic solvent and that of pure water becomes smaller than about 35, the adsorption and micellization behavior of the surfactants in different organic solvents–water mixed media shifts to those in pure water. Finally a comparison was made between the surface active imidazolium-based ionic liquids and traditional cationic surfactants in respect to the effects of organic solvents on their surface activity and aggregation behavior in aqueous solutions.

Effect of Biologically Significant Metal Complex Additives on the Micellar Properties of SDS

The effect of some biologically significant transition metal complexes such as [Fe(bpy)Cl4] [bpy-H], [Co(bpy)(phen)2](NO3)2·2H2O, [Fe(PDCl4][PD-H], [Cu(L)(NO3)2], [Cu(phen)2] Cl2·2H2O and [Cu(PD)(phen)2](NO3)2·2H2O (L=3,14-diethyl-2,6,13,17-tetraazatricyclo (16,4,07,12)docosane, bpy=2,2?-bipyridine, PD =1,10-phenanthroline-5,6-dione, phen=1,10-phenanthroline) on the critical micelle concentration (CMC) of an anionic surfactant, sodium dodecyl sulfate (SDS) were studied by conductance measurement method. The investigation was performed in the additives concentration ranging from 2.0 × 10-4 M to 8.0 × 10-4 M and at temperature ranging from 20°C to 35°C with an interval of 5°C. Different micellar parameters such as CMC, degree of counter ion dissociation (?), degrees of counter ion binding (f), binding constant (Kb) as well as thermodynamic parameters were determined using the conductivity data. © 2014 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. doi: http://dx.doi.org/10.3329/jsr.v6i3.17761 J. Sci. Res. 6 (3), 497-508 (2014)

Micellization Parameters of Six Gemini Quaternary Ammonium Surfactants from Measurements of Conductivity and Surface Tension

The micellization of six Gemini quaternary ammonium surfactants aqueous solutions has been investigated from measurements on specific conductivity as a function of surfactant concentration at different temperatures from (298.15 to 323.15) K. The micellization parameters such as the critical micellar concentration (CMC) and the degree of counterion dissociation (β), Gibbs free energy (ΔGmic), enthalpy (ΔHmic), and entropy (ΔSmic) of micellization are then obtained. It is shown that the conductometry measurements provide agreement of the CMC values at 298.15 K with the surface tension studies. With the rise of temperature, the values of CMC and β increase, while ΔGmic changes little. The linear plots of TΔSmic versus ΔHmic show the effects of enthalpy–entropy compensation. The length of alkyl chain and the spacer group of the Gemini surfactant have significant influences on micellization parameters.

Ionic liquids effect on critical micelle concentration of SDS: Conductivity, fluorescence and NMR studies

The effects of ionic liquids (ILs) 3-methyl-1-pentylimidazolium bromide, [C5mim][Br] and 1-heptyl-3-methylimidazolium bromide, [C7mim][Br] on the physicochemical properties of aqueous sodium dodecylsulfate (SDS) solutions were studied. Various micellar parameters such as critical micelle concentration (cmc), degree of counter ion dissociation (α), aggregation number (Nagg) as well as some thermodynamic parameters such as standard free energy of micellization (ΔGm0), standard enthalpy of micellization (ΔHm0) and standard entropy of micellization (ΔSm0) have been evaluated. Significant increase in cmc and decrease in counter ion binding along with decrease in Nagg was observed. 1H NMR technique was applied to reveal the solubilization site of ILs in the SDS micellar solutions.

Spontaneous Formation of Nanocubic Particles and Spherical Vesicles in Catanionic Mixtures of Ester-Containing Gemini Surfactants and Sodium Dodecyl Sulfate in the Presence of Electrolyte

Self-assembly of pure ester-containing cationic gemini surfactants, dodecyl esterquat, and dodecyl betainate geminis, and cation-rich catanionic mixtures of them with sodium dodecyl sulfate (SDS) were investigated using surface tension, electrical conductivity, dynamic light scattering (DLS), transmission electron microscopy (TEM) and cyclic voltammetry (CV) measurements in the absence and presence of KCl. Different physicochemical properties such as the critical micelle concentration (CMC), degree of counterion dissociation (αdiss), interfacial properties, morphology of aggregates, and interparticle interaction parameters were determined. Both geminis formed micelles in the absence of KCl, and mixing with SDS did not change the morphology; just a growth in micelle size was observed. However, the aggregation behavior of these geminis with respect to the position of the ester bond in the alkyl chain appeared completely different in the presence of KCl. Esterquat gemini formed cubic nanoparticles (or cobosomes) in the presence of [KCl] = 0.05 M and transformed into spherical micelles upon increasing the surfactant concentration. By contrast, betainate gemini formed vesicles in the presence of [KCl] = 0.05 M and subsequently converted to micelles as the surfactant concentration increased. The morphology of esterquat gemini (in the presence of 0.05 M KCl) after mixing with SDS changed from cubic nanoparticles (or cobosomes) to cylindrical nanoparticles coexistent with cobosomes. Betainate gemini remained vesicular upon mixing with SDS, and no dramatic structural change of aggregates took place. The morphology changes of aggregates upon mixing with SDS were explained from calculating the interactions between two gemini surfactants and SDS on the basis of regular solution theory.

Synthesis and Thermodynamic Properties of Rosin‐Based Cationic Gemini Surfactants

AbstractA series of rosin‐based cationic gemini surfactants with different spacer length (n = 2, 3, 4) were synthesized and characterized. Surface activity and micellization parameters including the critical micelle concentration, the degree of counterion dissociation, and thermodynamic functions of micellization in aqueous solutions have been investigated. Free energy perturbation was performed to study the enthalpy‐entropy compensation of the synthesized gemini surfactants in aqueous solutions. The experimental results showed that the micellization of rosin‐based gemini surfactants in aqueous solutions is a spontaneous and entropy‐driven process. The micellization process was found to follow the entropy–enthalpy compensation phenomenon.

The Effect of Ethanol on Nanostructures of Mixed Cationic and Anionic Surfactants

AbstractMicellization of tetradecyl trimethyl ammonium bromide (TTAB) and sodium dodecyl sulfate (SDS) in water–ethanol (ET) micellar solutions, with the weight percent of ET changing within the range 0–30, was studied by means of surface tension and conductivity measurements. Surface tension measurements also provided information about the dependence of the surface excess concentration, the minimum area per surfactant molecule, and the standard Gibbs energy of adsorption on the added weight percent of the organic solvent. Information about the degree of counterion dissociation and phase transition was obtained through conductivity measurements. Cyclic voltammetry (CV) and dynamic light scattering (DLS) was also employed to investigate the mixed micellar behavior of the binary mixtures. It was shown that an excess of cationic surfactant and ET resulted in a phase transition of vesicles and large micelles to mixed micelles. The regular solution theory approximation was used to determine various micellar parameters of ideal systems. The regular solution interaction parameter (β) suggests that the formation of mixed micelles is due to the synergistic interactions in the case of TTAB/SDS systems and becomes affected by the water/ET ratio.

Study on Micelle Formation of Three Homologous Surfactants in Aqueous Solution by Surface Tension, Conductivity, and Fluorescence Measurements

The detailed micellization behaviors of three homologous Gemini surfactants, 2-hydroxypropyl-1,3-bis (alkyldimethylammonium chloride) designated as C n -3(OH)-C n (n = 12, 14, 16), were studied by surface tension, conductivity and steady-state fluorescence measurements in the temperature range of 15.0°C to 35.0°C. The critical micelle concentration (cmc), thermodynamic parameters of micellization (, , and ), degree of counterion dissociation (α 0 ) at the cmc, and aggregation number (N agg ) were determined. The results showed that cmc of each surfactant had a minmum value as temperature changed. Value of α 0 increased while that of N agg decreased with the increment of the temperature. At a certain temperature, cmc and α 0 decrease while N agg increases with elongation of the alkyl chain in the surfactant molecule.

Micellisation thermodynamics of sodium lauroylsarcosinate in water–alcohol binary mixtures

Aggregation of sodium lauroylsarcosinate (SLS) in aqueous solutions of methanol, ethanol, propanol and ethylene glycol at 288–313 K has been determined from conductivity measurement in the range 0–20% v/v of additives. The precise values of the critical micelle concentration (CMC) and the degree of counter-ion dissociation of micelles were obtained at each temperature by fitting the specific conductivity-surfactant concentration curve to the integrated form of the Boltzmann-sigmoid equation. The CMC was found to increase with increase in additive concentrations in the case of methanol and ethylene glycol, while it decreases with increase in ethanol and propanol concentration. The equilibrium model of micelle formation was applied to obtain the thermodynamic parameters of micellisation. The Gibbs free energies were observed to vary only slightly with temperature and additive concentrations. Enthalpy–entropy compensation was observed for all the systems with a constant compensation temperature of ≈300 K and negative compensation enthalpy.

Aggregation properties and thermodynamics of micellization of gemini surfactants with diethyl ether spacer in water and water–organic solvent mixed media

The aggregation properties and thermodynamics of micellization of three cationic gemini surfactants (n–EO1–n) containing diethyl ether spacer group with varying carbon number (n=12, 14 and 16) in the hydrophobic tails have been studied in water and water–organic solvents mixed media over the range of temperature (298.15 to 328.15)K using the conductometric method. Ethylene glycol (EG) and 1,4-dioxane (DO) were used as organic co-solvents with three different volume percentages due to their unique nature than other solvents. With increasing tail length, the critical micellar concentration (cmc) of gemini surfactants decreased. The effect of the diethyl ether spacer group on aggregation behaviour has been compared with other reported spacer groups. The micellization process is delayed in the presence of organic co-solvents as compared to pure water giving a positive value for the Gibbs energy of transfer (ΔGtranso). The degree of counter ion dissociation (α) increases with increasing tail length of gemini surfactants. It also increases with increase in the percentage of organic co-solvents and it is more prominent in DO–WR than EG–WR mixed media. The standard Gibbs energy of micellization (ΔGmo) is found to increase with increasing volume percentage of an organic co-solvent and also with decrease in the chain length of gemini surfactants. The ΔGmo has been correlated with Gordon parameter. The ΔGmo increases with increasing temperature which is more prominent in the presence of high percentage of an organic co-solvent and also in the presence of an organic co-solvent with less polarity. The enthalpies of micellization in all cases are exothermic in nature. The compensation between the enthalpy and entropy for the formation of micellar aggregates has been observed.

Influence of Glycerol and Temperature on the Phase Behavior and Micellization of CTAB and SDS in Aqueous Solutions

In this work the micellization of sodium dodecylsulfate (SDS) and cetyltrimethyammonium bromide (CTAB) in water-glycerol mixed solvent have been investigated at 25, 35, and 45°C, respectively. The micellization of both surfactants in pure water at different temperatures has also been studied. The phase diagrams of the surfactants in water-glycerol mixed solvent were also established. From the conductivity measurements, the critical micelle concentration (CMC) and the degree of counterion dissociation (β) were obtained as a function of glycerol-water ratio and temperature. Standard free energy of micellization (ΔG°mic) as a function of glycerol contents and temperature was calculated and discussed. It has been found that the micellization of the two surfactant in solutions with glycerol at 25°C and in pure water at higher temperatures are not the same although they have equal dielectric constants values.

CTAB aggregation in solutions of higher alcohols: Thermodynamic and spectroscopic studies

The effect of organic additive, C8–OH and C9–OH (octan-1-ol and nonan-1-ol) on the micellar behavior of aqueous solution of cetyltrimethylammonium bromide, CTAB was examined by thermodynamic (density and speed of sound) measurements. The polar compounds form the additive-CTAB mixed micelles which cause micellar growth. The critical micelle concentration, cmc, and degree of counterion dissociation, α, of aqueous solution of CTAB containing different amounts of monohydric alcohols have been determined at various temperatures by means of electrical conductivity. Fluorescence method has also been used to obtain cmc values as well as the aggregation number, Nagg, of CTAB in the presence of studied alcohols. In general, the experimental results indicate that micelle formation is hindered by a rise in temperature. In addition, alcohols show an inhibitory effect on the formation of micelles of CTAB. The results are well supported by spectral studies viz. fluorescence and NMR.

Synthesis and Physico‐Chemical Studies of Ester‐Quat Surfactants in the Series of (Dodecanoyloxy)propyln‐Alkyl Dimethyl Ammonium Bromide

AbstractEster‐quat surfactants in the series of (dodecanoyl oxy) propyln‐alkyl dimethyl ammonium bromide referred to here as LC3Cm(wheremis the hydrocarbon chain lengths 8, 12 and 14) were synthesized and characterized by the usual spectroscopic methods (NMR, IR, MS…). Their physico‐chemical properties were investigated by surface tension and conductimetric measurements. From surface tension measurements, isotherms and thermodynamic adsorption parameters were determined. The critical micelle concentration (CMC), the degree of counter ion dissociation (α) of micelles in the water and the standard Gibbs free energy, of micellization were also determined by conductimetric measurements. The results obtained from both methods were compared to the similar surfactants in the series of quaternary ammonium surfactants. Optical microscopy was also used to study the behavior of anhydrous surfactants and the binary water/surfactant system as a function of temperature.

A Thermodynamic Study of Micellization of 3-Alkyloxy-2-hydroxypropyl Trimethylammonium Chloride in Aqueous Solution

The detailed micellization behavior of 3-alkyloxy-2-hydroxypropyl trimethylammonium chloride (RnHTACl, n = 12, 14, 16) in aqueous solution was studied by electric conductivity, steady-state fluorescence, and isothermal titration microcalorimetry (ITC) methods. The critical micelle concentration (CMC) and degree of counterion dissociation (α0) were estimated from conductivity curves in the temperature range of 293.15 K to 323.15 K. Then the thermodynamic parameters of micellization (ΔGm0, ΔHm0, and ΔSm0) were calculated by applying a mass-action model equation. On the basis of the ITC results, the CMCs and thermodynamic parameters were also estimated at 293.15 K, which were basically consistent with the results from the conductivity method. According to the Turro–Yekta method, the micelle aggregation number (Nagg) of RnHTACl was determined through static luminescence quenching, and found that the decreased temperature, the elongation of the alkyl chain length or the increased concentration of RnHTACl could...

Influence of water-insoluble nonionic copolymer E6P39E6 on the microstructure and self-aggregation dynamics of aqueous SDS solution—NMR and SANS investigations

The influence of water-insoluble nonionic triblock copolymer PEO-PPO-PEO [poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)] i.e., E6P39E6 with molecular weight 2800, on the microstructure and self-aggregation dynamics of anionic surfactant sodium dodecylsulfate (SDS) in aqueous solution (D2O) were investigated using high resolution nuclear magnetic resonance (NMR) and small-angle neutron scattering (SANS) measurements. Variable concentration and temperature proton ((1)H), carbon ((13)C) NMR chemical shifts, (1)H self-diffusion coefficients, (1)H spin-lattice and spin-spin relaxation rates data indicate that the higher hydrophobic nature of copolymer significantly influenced aggregation characteristics of SDS. The salient features of the NMR investigations include (i) the onset of mixed micelles at lower SDS concentrations (<3 mM) relative to the copolymer-free case and their evolution into SDS free micelles at higher SDS concentrations (~30 mM), (ii) disintegration of copolymer-SDS mixed aggregate at moderate SDS concentrations (~10 mM) and still binding of a copolymer with SDS and (iii) preferential localization of the copolymer occurred at the SDS micelle surface. SANS investigations indicate prolate ellipsoidal shaped mixed aggregates with an increase in SDS aggregation number, while a contrasting behavior in the copolymer aggregation is observed. The aggregation features of SDS and the copolymer, the sizes of mixed aggregates and the degree of counterion dissociation (α) extracted from SANS data analysis corroborate reasonably well with those of (1)H NMR self-diffusion and sodium ((23)Na) spin-lattice relaxation data.

Thermodynamic Study of a Cationic Surfactant in Aqueous Solution Containing Ethylene Glycol and Its Oligomers: Effect of Number of Ethereal Oxygen Atoms in Glycols Molecule

Effect of glycols viz., ethylene glycol (EG), diethylene glycol (DEG), triethylene glycol (TEG) and tetraethylene glycol (TeEG) on micellization parameter of cationic surfactant tetradecyletrimethyl ammonium bromide (TTAB) was examined by means electrical conductivity measurements. The critical micelle concentration (CMC), degree of counterion dissociation (α) and Gibbs energy of micellization (ΔGm) as well as Gibbs energy of transfer (ΔG t ) of surfactant tail from bulk phase to micellar phase as a functions glycol concentration at 303.15 K were evaluated. In ordered to obtain enthalpy (ΔHm) and entropy (ΔSm) of micellization, CMCs were determined in 10.0% of glycols in temperature range from 303.15 K to 323.15 K. Thermodynamic parameters of the micellization reveal that effectiveness of glycols to reduce micellization increases with concentration and with number of ethereal oxygen, [-O-]n in glycol molecule.

Surface Activity and Micellization Parameters of Quaternary Ammonium Surfactants Containing a Hydroxyethyl Group

Based on the measurements of conductivity and surface tension and our previously reported results of isothermal titration calorimetry (ITC), the surface activity and micellization parameters, such as the critical micellar concentration (CMC), the degree of counterion dissociation (β), and thermodynamic functions of micellization, for six quaternary ammonium surfactants, dodecyl-(2-hydroxyethyl)-dimethylazanium bromide, tetradecyl-(2-hydroxyethyl)-dimethylazanium bromide, hexadecyl-(2-hydroxyethyl)-dimethylazanium bromide, dodecyl-di(2-hydroxyethyl)-methylazanium bromide, tetradecyl-di(2-hydroxyethyl)-methylazanium bromide, and hexadecyl-di(2-hydroxyethyl)-methylazanium bromide in aqueous solutions have been investigated. The values of CMC determined from three different methods are compared, and they show reasonable agreement. From the CMC values obtained from the conductivity measurements in this work and the previously reported values of calorimetric enthalpy of micellization, the Gibbs free energy (ΔGm...

Influence of 1,4-dioxane on the aggregation of bis(tetradecyldimethylammonium)butane dibromide gemini surfactant

The aggregation behavior of bis(tetradecyldimethylammonium)butane dibromide (14-4-14, 2Br-) gemini surfactant in various compositions of 1,4-dioxane–water (DO–WR) mixed media across a range of temperatures has been investigated by means of electrical conductivity and steady state fluorescence quenching measurements. The parameters determined and discussed include critical micelle concentration (cmc), degree of counter ion dissociation (α), average aggregation number (Nagg) and micropolarity (I1/I3). The thermodynamic parameters of micellization were computed from the temperature dependence of the cmc. At a fixed temperature, adding DO to the solvent medium causes an increase in cmc, an initial declination and further increase in α and a regular decrease in Nagg. The micropolarity of the medium around the pyrene in the presence of 14-4-14, 2Br− micelles remains almost the same up to 20% DO and shows increase in 30 and 40% DO media while in the absence of 14-4-14, 2Br− a regular decrease was obtained. Thermodynamic analysis shows that, although micellization is less favored in DO–WR mixed media than in water, the process is spontaneous and exothermic. Compensation of enthalpy and entropy of micellization of 14-4-14, 2Br− is observed in the DO–WR mixed media.

Micellization and Thermodynamic Parameters of Butanediyl-1,4-bis(tetradecyldimethylammonium Bromide) Gemini Surfactant at Different Temperatures: Effect of the Addition of 2-Methoxyethanol

The effect of the addition of 2-methoxyethanol on the critical micelle concentration (cmc) and on the degree of counterion dissociation (α) of butanediyl-1,4-bis(tetradecyldimethylammonium bromide) gemini surfactant, [C14H29N+(CH3)2–(CH2)4–N+(CH3)2C14H29,2Br−] (referred as 14–4–14,2Br−), has been studied by varying the compositions of the 2-methoxyethanol + water mixed solvent media (0 to 50 %). To determine various thermodynamic parameters of micellization, on the basis of the mass–action model for micelle formation, the experiments were performed at selected compositions of the mixed solvent at four temperatures ranging between 25 °C and 50 °C. Furthermore, the air/bulk surface tensions of the pure and mixed media were determined, and a successful attempt was made to correlate the cohesive energy density described through the Gordon parameter with the values of Gibbs energy of micellization.

Aqueous Solution Behavior of Cationic Surfactant Modulated by the Presence of Glycols and Their Ethers

Abstract The effect of ethylene glycol (EG), diethylene glycol (DEG) and their monoalkyl (C1–C6) ethers (cellosolves and carbitols) and dimethyl ethers (glymes and diglymes) on the micellar behavior of a cationic surfactant tetradecyltrimethylammonium bromide (TTAB) in aqueous solution was examined from electrical conductivity measurements. The effect of these additives on critical micelle concentration (CMC) and degree of counter ion dissociation (α) is evaluated. While both EG, DEG, their monomethyl/monoethyl ethers and dimethyl ethers increased CMC and α, for monobutyl and monohexyl ethers a decrease in CMC was noticed at studied concentration. For all ethers, the α values increased with concentration. NOESY experiments confirmed the location of glycol ethers in micellar solution. The results are discussed in terms of effect of ethers on water structure and solvent properties.