Degree Of Counterion Dissociation Research Articles

Effect of solvent and temperature on the micellization and thermophysical properties of cetyltrimethylammonium bromide

The Micellization is the fundamental phenomenon in colloid and surface chemistry which plays a pivotal role in a multitude of industrial processes, biological systems, and everyday applications. In this study, we investigate the micellization behavior of the cationic surfactant, cetyltrimethylammonium bromide (CTAB) within aqueous and ethanol–water mixtures across a temperature range. The electrical conductivity measurements unveil insights into the critical micelle concentration (CMC) and the degree of counterion dissociation (β) at each temperature. Notably, as ethanol content increases in the solvent, both CMC and β values exhibit a corresponding uptick. These findings enable the assessment of standard Gibbs free energy (ΔGmic0). Furthermore, our investigation extends to find out the thermophysical properties (viz., density, dynamic viscosity, and kinematic viscosity) assessments across varying ethanol compositions and temperatures. These metrics facilitate the calculation of activation energy for mixed systems. The implications of these results (data) could be useful for both the fundamental as well applied research, and promise valuable insights for future endeavors.

Investigation of micellization and thermodynamic properties of cationic gemini surfactant (12-2-O-2-12) in the presence of organic solvents

The micellization behaviour and thermodynamic properties of synthesized cationic gemini surfactant (12-2-O-12-12), N,N′-didodecyl-N,N,N′,N′-tetramethyl-N,N′-(oxybis(ethane-2,1-diyl))-diammonium dibromide were studied in the presence of organic solvents for four different temperatures (25, 30, 35 and 40 °C). Aqueous solutions of 10 % and 20 % methanol (MeOH), ethanol (EtOH), isopropanol (IPOH) and dimethyl sulfoxide (DMSO) were used as solvents. The critical micelle concentration (CMC) of cationic gemini surfactant and the degree of counterion dissociation (α) were determined by the conductometric method. Using the CMC and α values for each of the four temperatures, the values of the standard Gibbs free energy (ΔGmo), Gibbs free energy of transfer (ΔGm,transo), enthalpy (ΔHmo), and entropy (ΔSmo) of micellization were calculated. It was observed that the CMC and α values increased with increasing solvent percentage and temperature. It was found that in all cases, the standard Gibbs free energy and enthalpy values were negative while both the micellization entropy and the standard Gibbs free energy of transfer are positive. Negative Gibbs free energy values indicated that micellization was a spontaneous situation, while positive entropy values indicated the existence of a disordered situation. The positive ΔGm,transo values show that the presence of solvents makes the environment unfavorable for micelle formation.

Cheap and effective potentiometric PVC sensor for the determination of imidazolium based ionic liquids in aqueous and aqua-organic media

Owing to the extensive research on imidazolium based ionic liquids; the present study aims to design a potentiometric sensor for alkyl methylimidazolium ion. For this, poly(vinyl chloride) PVC membrane based on the neutral ion-pair complexes of cetylpyridinium chloride and sodium dodecyl sulfate (CPy+DS−) has been developed. The synthesized ion selective electrode (ISEs) have been found to show linear response with near-Nernstian slope for CnMeImCl (C10MeImCl, C12MeImCl and C14MeImCl). The proposed ISEs show quick response (5–6 s) and provide wide pH range for working. The influence of various ions on the performance of ion-selective electrode is investigated in terms of potentiometric selectivity coefficients, which were determined by separate solution method. The performance of synthesized ISE in examining the critical micellar concentration (cmc) of CnMeImCl in aqueous, aqua-organic media and in the presence of amino acids (glycine, L-glutamic acid and L-phenylalanine) has been found to be satisfactory and confirmed through conductivity and fluorescence measurements. This emphasizes its worth for in-situ analysis of alkyl methylimidazolium ions, during an organic reaction, and hence possible reaction mechanism evaluation. Different thermodynamic parameters such as Standard Gibbs energies of micellization (ΔGm∘), degree of counterion dissociation (α), amphiphile tail transfer Gibbs free energy (ΔGm,trans∘) have been evaluated. Further, the analytical application of synthesized electrode as end point indicator in the potentiometric titration of C14MeImCl with SDS has also been explored, which compared well with improved two-phase titration method. The current study is novel as it involves the use of a cheaper material (CPyCl) as ionophore and that the same electrode can be used for different chain alkyl methylimidazolium ions simply by changing the internal reference solutions.

Exploring the Impact of Cationic Surfactant Ctab on Bleu Brilliant G 250 De Cosmassie: Implications for Health Management and Environmental Sustainability

Background: Surfactants are ubiquitous in both natural and industrial processes due to their unique ability to reduce surface tension and facilitate interactions between hydrophilic and hydrophobic substances. Cationic surfactants like cetyltrimethylammonium bromide (CTAB) are of particular interest because of their widespread applications in areas such as healthcare and environmental management. The interaction between surfactants and dyes, such as Bleu Brilliant G 250 de Cosmassie, is critical in industrial processes, especially in the textile industry where wastewater treatment poses significant environmental challenges. Objective: The aim of this study was to explore the thermodynamic behavior of CTAB when combined with Bleu Brilliant G 250 de Cosmassie in aqueous solutions at room temperature. It sought to determine the critical micelle concentration (CMC) and the degree of counter-ion dissociation (α), and to calculate the changes in Gibbs free energy (ΔGm), enthalpy (ΔHm), and entropy (ΔSm) of the system. Methods: The study employed conductometric and spectrophotometric techniques to analyze the CTAB-dye interactions. Solutions were prepared with varying concentrations of CTAB and Bleu Brilliant G 250 de Cosmassie in deionized water, ensuring solvent purity through stringent conductivity and pH monitoring. Electrical conductance was measured at different temperatures to determine the CMC, while absorbance spectra were recorded to observe changes in the interaction between the surfactant and dye. The degree of counter-ion dissociation was calculated by the slope ratio method, and thermodynamic parameters were computed using established equations. Results: The conductometric studies revealed an increase in CMC with temperature, indicating a stabilization of surfactant monomers at higher temperatures. For CTAB and Bleu Brilliant system 1, the CMC was found to be 0.8 with α valued at 0.83. For system 2, the CMC values were 1.55 and 1.6 with α values of 1.01 and 0.91, respectively. Thermodynamically, the system displayed a Gibbs free energy of micellization of -33.09 KJ/mol, an enthalpy change of -6.53, and an entropy change of 0.1325 JK^-1 mol^-1. Conclusion: The study concluded that the interaction between CTAB and Bleu Brilliant G 250 de Cosmassie is influenced significantly by temperature, which affects the micellization behavior and thermodynamic properties. The findings contribute to a better understanding of the fundamental thermodynamic parameters influencing surfactant-dye interactions, providing insights that may improve industrial processes and environmental sustainability.

Impacts of pyridinium gemini surfactants on corrosion inhibition of carbon steel

Pyridinium gemini surfactants (PGS-n) are an important class of amphiphiles with antibacterial properties and hence, are usually preferred in industrial and medicinal applications. In this work, three PGS-n with different alkyl chain lengths having two amide spacers, 3,3′-(Malonylbis(azanediyl))bis(1-dodecylpyridin-1-ium) dibromide (PGS-12), 3,3′-(Malonylbis(azanediyl))bis(1-tetradecylpyridin-1-ium) dibromide (PGS-14), and 3,3′-(Malonylbis(azanediyl))bis(1-octadecylpyridin-1-ium) dibromide (PGS-18), were synthesized, characterized and tested as corrosion inhibitor on carbon steel in HCl for the first time. The corrosion inhibition efficiency was examined by weight loss measurement, electrochemical impedance spectroscopy (EIS), and potentiodynamic measurements at 30 °C. Furthermore, micellization parameters such as critical micelle concentration (cmc), degree of counter ion dissociation, and Gibb's energy of micellization of these PGS-n were determined. The inhibition efficiency of the studied PGS-n was found to be maximum near their cmc values and found to follow the order: PGS-18 > PGS-14 > PGS-12. The PGS-n with the longest alkyl chain could achieve a maximum inhibition efficiency of 99.2 %. The adsorption of PGS-n on the surface of carbon steel was found to follow the Langmuir adsorption isotherm. The results obtained from EIS measurements agreed well with those of polarization and weight loss studies. Field emission scanning electron microscopic analysis revealed that the corrosion of the carbon steel surface is not severe, especially in the presence of PGS -18. Density functional theory was employed to calculate various quantum chemical parameters of the PGS-n. The results suggest PGS-n as an effective inhibitor for corrosion inhibition of carbon steel.

Molecular interactions of cationic/anionic surfactants in presence of anionic antibiotic drug cloxacillin sodium at different temperatures: Micellization and thermodynamic studies

The physicochemical properties and interactions of surfactant–drug aggregates are regarded as essential features to achieve optimum therapeutic action of the drug. In this article, the effect of various concentrations of anionic antibiotic drug cloxacillin sodium (ClxNa) on the micellization of cationic surfactants such as cetyltrimethylammonium bromide (CTAB), tetradecyltrimethylammonium bromide (TTAB) and anionic surfactant sodium dodecyl sulphate (SDS) have been investigated using electrical conductance measurement at different temperatures (288.15 K, 293.15 K, 298.15 K, 303.15 K, 308.15 K, and 313.15 K). The results suggest an increase in critical micelles concentration (CMC) values for cationic surfactants (CTAB/TTAB) with a rise in drug concentration (0 mM up to 10 mM) whereas anionic surfactant SDS shows a decrease in CMC at higher drug concentrations (from 2.5 mM up to 10 mM) at all the studied temperatures. The degree of counterion dissociation (α) values for TTAB aggregates show a slight increase with [ClxNa], except at a few lower temperature ranges whereas such a regular trend was not obtained for CTAB and SDS aggregates. Temperature-dependent CMC values show a nonlinear nature with a rise in temperatures and follow a U-shaped curve for all studied pure surfactant and surfactant–ClxNa systems. Micellization for all surfactant-drug systems is found to be spontaneous. Investigation of other temperature-dependent thermodynamic parameters such as change in standard enthalpy (ΔHm0), and entropy (ΔSm0) of micellization suggest that surfactant–drug interactions are both endothermic (ΔHm0 < 0, particularly at lower temperatures) and exothermic (ΔHm0 < 0, at higher temperatures), whereas micellization is largely entropically driven (ΔSm0 > ΔHm0).

Exploring the effects of interactions between nonylphenol ethoxylate and ionic surfactants on interfacial and foaming properties

Nonylphenol ethoxylate (NPE-9) is a widely recognized non-ionic surfactant that finds extensive applications in various industries, including detergency, emulsification, and agriculture. Combining NPE-9 with an ionic surfactant reflects an inexpensive and highly promising approach for enhancing the efficacy of NPE-9. This study explores the molecular interactions between NPE-9 and ionic surfactants (SDS and CTAB) and examines the impact of these interactions on interfacial properties and foaming. The micellization parameters, including the critical micelle concentration (CMC), degree of counterion binding (β), degree of counterion dissociation (α), and change in free energy of micellization (ΔGmic), were investigated for sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) in the presence and absence of NPE-9, using conductometric measurements. The combined effect of NPE-9 and an ionic surfactant resulted in a synergistic interaction, reducing the CMC of the ionic surfactant, and promoting the formation of micelles. The interaction between NPE-9 and ionic surfactants at the air/water interface was investigated using surface tension measurements. The interfacial properties improved through the competitive adsorption and synergistic effect observed between NPE-9 and an ionic surfactant. In this context, the surface tension data of NPE-9 is utilized to calculate interfacial parameters, including maximum surface excess concentration (Γmax), minimum area per molecule (Amin), and surface effectiveness (π). Adding SDS and CTAB to NPE-9 solutions resulted in a notable enhancement in foamability and foam stability. The utilization of various techniques consistently produced improvements in the interfacial and foaming properties of NPE-9.

Effects of head-group volume on the thermodynamic parameters and species distribution of ionic liquid-based surfactants in water: 1-(n-hexadecyl)-3-alkylimidazolium bromides and chlorides

The following series of ionic liquid-based surfactant halides was studied: 1-(n-hexadecyl)-3-Cm-imidazolium bromides and chlorides (C16CmImBr and C16CmImCl, respectively) where Cm = C1-C4. Using isothermal titration calorimetry, we calculated the enthalpy of micelle formation (ΔH⁰mic) at 25 °C for both halide surfactants, and from 15 to 70 °C for C16CmImCl. Values of ΔH⁰mic were then employed to calculate the entropy of micelle formation (ΔS⁰mic) from the corresponding free energy (ΔG⁰mic); the latter was calculated from the critical micelle concentration (cmc) and the degree of counter-ion dissociation (αmic). Values of ∣ΔG⁰mic∣ increase as a function of increasing Cm, although this increase is smaller than that of the previously studied series CnC1ImCl, where Cn = C10 to C16. This is attributed to the difference in dehydration of the surfactant segments that accompanies micelle formation, which is much larger for the increase in the hydrophobic chain (CnC1ImCl) than for the head-group (C16CmImCl). The calculated enthalpograms (ΔH⁰dilution versus [surfactant]) for C16C4ImBr showed deviation from ideal solution behavior, this was attributed to the formation of premicellar aggregates. The latter conclusion was corroborated by Pulsed Field Gradient (PFG)-NMR experiments of C16CmImCl in D2O. Thus, a model based on the presence of the following species in solution fitted satisfactorily the dependence of the observed surfactant diffusion coefficients on [surfactant]: free surfactant molecules; premicellar aggregates and micellized surfactant. The concentration of the premicellar aggregates increases noticeably as a function of increasing Cm, due to hydrophobic interactions between the Cm groups. The solubilization of (anionic) thymol blue indicator by C16CmImBr was studied using UV–Vis spectroscopy. The solubilization power (=moles of solubilized molecule/mole of micellized surfactant) was calculated, and compared with our previous data on the solubilization of (hydrophobic) Sudan IV dye and (less hydrophobic) drug nitrendipine by C16CmImBr. In all cases, the solubilization power decreases as a function of increasing Cm, albeit to different degrees, due to a combination of steric hindrance by the head-group, and decreased micelle size, both acting in the same direction.

Micellar properties of cetyltrimethylammonium bromide in an acetonitrile–water mixture: Conductometric and fluorescence studies

The effect of acetonitrile (ACN) on the micellization of a cationic surfactant, cetyltrimethylammonium bromide (CTAB), in aqueous solutions at different temperatures was studied. The critical micellar concentration (CMC) as well as the degree of counter ion dissociation (a) of CTAB in aqueous ACN mixtures (10-20 % v/v) at various temperatures (291.2-298.2 K) were determined by electrical conductivity measurements, while steady-state fluorescence measurements were used to determine several CMCs (for comparison) and a micellar aggregation number (Nagg) as well. At a fixed temperature, both an increase in CMC and a decrease in Nagg were observed for an increase in ACN in the solvent mixture. With a temperature increase, CMC values increased for 10 % (v/v) ACN, while for both 15 % and 20 % (v/v) ACN, CMC values were a minimum at T = 295.2 K with a temperature increase. In addition, some aspects related to the Krafft temperature behavior of CTAB in the examined micellar systems are discussed.

Studies on thermodynamics of micellization of imidazolium-based surface-active ionic liquid [C15mim][Br] in aqueous media: Effect of D(+)-Xylose and D(+)-Glucose

Owing to the extensive applications of surfactant-based systems, it is of extreme importance to understand the influence of various external additives on the system properties of surfactant solutions. Ionic liquids with long alkyl chain are extensively researched for their properties as surfactants. Herein, the micellization properties of the IL, [C15mim][Br] in the absence and in the presence of different concentrations of D(+)-Xylose and D(+)-Glucose as external additives have been scrutinized using numerous techniques such as electrical conductivity, UV–Visible, Fluorescence and FT-IR measurements at (298.15, 303.15 and 308.15)K. The values of important physicochemical properties essentially, CMC, degree of counter-ion dissociation, and various thermodynamic parameters which have been computed from conductivity measurements. The CMC values obtained using UV–Vis and Fluorescence technique also validate the results from conductivity measurements. Analyses of CMC values indicate that the studied carbohydrates promote the micellization of IL in the order: D(+)-Glucose > D(+)-Xylose as a consequence of their solute-out effect.

Systematic Studies of Sodium γ-Octyl Aspartate to evaluate its Biodegradation, Surface Parameters, Micellization Aspects and Thermodynamic Properties of its Binary Mixture using Electrolytes

γ-octyl aspartate has been synthesized with 46.2% yield. The optimized conditions for esterification of aspartic acid and n-octanol are 24 hours duration and 1:1 molar ratio of reactants (aspartic acid: n-octanol). FT-IR, 1H NMR and CHNS element analysis techniques are used for structure elucidation of γ -octyl aspartate. Surface/ interfacial studies, micellization aspects, thermodynamic parameters, biodegradability and binary salt behaviour of sodium γ-octyl aspartate have been studied. The CMC of synthesized surfactants was 0.0078 mol/L, whereas minimum surface area per surfactant molecule was calculated as 29.49 Å2m2; calculated aggregation number was 34 and micelle radius (r) found to be 1.40 nm. The degree of counter-ion dissociation (α) was determined to be 0.86. Thermodynamic parameter - standard free energy of adsorption (ΔG0ads) was calculated as -18.70 kJ/mol. The shape of micelle of synthesized surfactant was noticed to be spherical but during binary studies in some cases, it was found to be cylindrical. OECD and Winkler’s method were used to determine biodegradation of sodium γ-octyl aspartate found to be 95.1 %.

Synthesis, Characterization, Antibacterial Activity, and Interfacial and Micellar Features of Novel Cationic Gemini Surfactants with Different Spacers

AbstractIn the present study, four novel imidazolium‐based cationic gemini surfactants (IBCGS) have been synthesized, having same hydrocarbon chain lengths and different spacers. The impacts of type and nature of spacer on Krafft temperatures (TK) have been examined. Micellization behaviors of IBCGS have been investigated at different temperatures above TK by both surface tension and specific conductivity measurements. Surface activity properties of aqueous systems have been calculated using the results of the measurement data. Critical micelle concentration (CMC), surface pressure at CMC (ПCMC), minimum area of head group (Amin), degree of counterion binding (β), degree of counterion dissociation (α), and maximum surface excess (Γmax) of IBCGS have been calculated with data of surface tension and specific conductivity. IBCGS have low CMC values than other imidazole categories of gemini and monomeric cationic surfactants. Micelle aggregation number (Nagg) values have been determined with the steady‐state fluorescence quenching method. The values of Nagg have been found in the range of 19–28. Additionally, the antibacterial activities of IBCGS on gram‐positive and gram‐negative bacteria have been investigated. IBCGS studied in this article have showed perfect antibacterial activity particularly against gram‐positive bacteria. The data obtained in this study may be benefical for the surfactant applications in different areas.

On the effects of head-group volume on the adsorption and aggregation of 1-(n-hexadecyl)-3-Cm-imidazolium bromide and chloride surfactants in aqueous solutions

The effects of the length of alkyl side chain (Cm) of ionic liquid-based surfactants (ILBSs) on their adsorption at the water/air interface, and aggregation in aqueous solutions were investigated for the series 1-(n-hexadecyl)-3-Cm-imidazolium bromides and chlorides, where Cm = C1-C4 for the bromides, and C1-C5 for the chlorides. These physicochemical properties were calculated from surface tension, conductivity, and fluorescence data. It was found that increasing the length of Cm (i.e., volume of the head group) leads to enhancement of surface activity, increase in the area per surfactant molecule at the water/air interface (Amin) and the degree of counter-ion dissociation (αmic). Our data also indicated that increasing the volume of the head group results in a decrease of the critical micelle concentration (cmc), Gibb's free energy of adsorption and micellization, and microscopic polarity of interfacial water. In order to delineate the effects of the presence of unsaturation in the HG, we included members that carry Cm = vinyl and allyl in the bromide series. The effect of these groups was found to be similar to removing a methylene group from Cm. The dependence of the solubilization of a lipophilic dye (Sudan IV) and a drug (nitrendipine) on the length of Cm was also studied.

Aggregation Behavior of Mixed Micellar System of Dodecyl Sulfate‐Based Surface‐Active Ionic Liquids and Anionic Surfactant in Aqueous Media

AbstractMixed micellization behavior of dodecyl sulfate‐based ionic liquids, i.e., 1‐propyl‐3‐methylimidazolium dodecyl sulfate [C3mim][DS] and 1‐hexyl‐3‐methylimidazolium dodecyl sulfate [C6mim][DS] with sodium dodecyl sulfate (SDS), is investigated at (298.15, 308.15, and 318.15) K in aqueous medium. For this, the conductometric measurements are carried out to evaluate the critical micelle concentrations (cmc), ideal critical micelle concentration (cmc*), degree of counterion dissociation (g), thermodynamic parameters, micellar mole fraction of ionic liquids, and interaction parameter (β) of the mixed system based on the different proposed models given in the literature. Further surface tension measurements have been carried out to confirm the value of cmc obtained via a conductivity study for all the studied systems at 298.15 K. Other surface parameters, such as surface tension at cmc (γcmc), surface pressure (ᴨcmc), surface excess (Γmax), and minimum area per molecule (Amin), have also been evaluated for both the systems.

Exploring the effect of hydrophobic ionic liquid on aggregation, micropolarity and microviscosity properties of aqueous SDS solutions

Ionic liquid (IL)-modified surfactant systems have versatile applications in several technological areas. Therefore, it is utmost need to achieve full understanding of interactions existing in such systems before their further uses. Here, the effects of IL, 1-ethyl-3-methylimidazolium hexafluorophospahte, [emim][PF6] on the physicochemical properties of aqueous sodium dodecyl sulfate (SDS) solutions has been studied using multi-technique approach. Various micellar parameters such as critical micelle con-centration (cmc), degree of counter ion dissociation (α), aggregation number (Nagg) as well as some thermodynamic parameters such as standard free energy of micellization (G°m), standard enthalpy of micellization (H°m) and standard entropy of micellization (S°m) and surface properties from surface tension measurement have been evaluated. A significant decrease in cmc, and increase in degree of counter ion dissociation along with increase in Nagg is observed. The aggregation behaviour of SDS is also studied in presence of ILs having different alkyl chain length in their imidazolium cations. A decrease in CMC of SDS observed, and trend of decrease in CMC is reported as [hmim][Cl] > [bmim][PF6] > [emim][PF6]. The micropolarity and microviscosity of micellar media are accessed with fluorescence probe studies. The effect of chain length of IL cation has been also explored on aggregation behaviour. The FTIR technique is employed to evaluate possible interactions between SDS and IL [emim][PF6] molecules, the information regarding size of SDS micelle in presence of IL [emim][PF6] has been explored by DLS technique.

Cationic gemini surfactants containing both amide and ester groups: Synthesis, surface properties and antibacterial activity

Nine novel cationic gemini surfactants containing both amide and ester groups were synthesized through a three-step reaction. These surfactants have the general formula of CnH2n+1OOCCH2N+(CH2)2-(CH2)3-NHOC-(CH2)m-CONH-(CH2)3-N+(CH2)2CH2COOCnH2n+1 (with n = 8, 10, 12 and m = 2, 3, 4), named BEQA-n, PEQA-n and HEQA-n (B, P, H correspond to surfactants of m = 2, 3, 4 and n = 8, 10, 12, respectively). Chemical structures, surface activity, cleavable properties, electrolytes tolerance, foam properties and antibacterial activity of these surfactants were successively investigated. The results show that the surfactants have lower critical micelle concentration (CMC) than traditional monomer surfactants. The values of CMC and the degree of counter ion dissociation (α) depend on the lengths of hydrophobic chain and spacer. The values of Krafft temperatures (Kt < 0 °C) and the standard Gibbs free energy (∆G0mic < 0) indicate that all surfactants have good water solubility and micelle-forming ability. The simultaneous presence of the amide and ester groups makes these surfactants have good hydrolytic ability in both basic and the acidic solutions. In addition, the surfactants exhibit greater electrolyte tolerance to NaCl than CaCl2. It is worth mentioning that EQA-8 and PEQA-12 have 200 g/L NaCl tolerance. Moreover, all of the surfactants have certain antibacterial activity against Gram-positive bacteria (S. aureus ATCC 25923) and Gram-negative bacteria (E. coli ATCC 25922), and the surfactants with hydrophobic chain length n = 10 have the strongest antibacterial activity.

Co-solvent Effect on Spontaneous Formation of Large Nanoscale Structures in Catanionic Mixtures in the Anionic-Rich Region

The aggregation behavior was investigated in mixtures of sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) (anionic-rich catanionic) solutions. The study was conducted in solutions of water–ethylene glycol (EG) by means of surface tension, conductometry, cyclic voltammetry, zeta potential measurements, transmission electron microscopy (TEM) and dynamic light scattering (DLS) techniques. The degree of counterion dissociation (α), critical micelle concentration, aggregation numbers, interfacial properties, interparticle interaction parameters, and morphology of aggregates were determined. Based on regular solution theory, the cosolvent effects between SDS and CTAB as surfactants were also analyzed for both mixed monolayers at mixed micelles (βM) and the air/liquid interface (βσ). It was shown that the formation of large aggregates occurred in the presence of an excess of anionic surfactant. A phase transition from cylindrical micelles to spherical micelles in the anionic-rich regime was observed with an increase in the EG volume fraction. The inter particle interactions were assessed in terms of cosolvent effects on the micellar surface charge density and the cylindrical-to-spherical morphology change. Zeta potential and size of the aggregates were determined using dynamic light scattering and confirmed the models suggested for the processes taking place in each system.

Mixed micellization behaviour of tri-substituted surface active ionic liquid and cationic surfactant in aqueous medium and salt solution: Experimental and theoretical study

The aim of the present study is to investigate the mixed micellization behaviour of trisubstituted surface active ionic liquid (SAIL) 1-tetradecyl-2,3-dimethylimidazolium bromide [C14bmim][Br] and cationic surfactant cetyltrimethylammonium bromide (CTAB) in aqueous solution and in the presence of inorganic salt, sodium bromide (NaBr) using the conductivity, steady-state fluorescence and 1H NMR measurements. The degree of counter-ion dissociation (g), critical micelle concentration (cmc), various thermodynamic parameters of micellization (ΔGm0, ΔHm0 and ΔSm0) have been evaluated from conductivity measurements. All these parameters show that strong synergistic interactions have been observed in the studied mixed systems in the aqueous medium and the presence of salt promotes the electrostatic interactions that result in lowering of cmc values. The aggregation number (Nagg) of mixed micelle has been ascertained from steady-state fluorescence quenching indicate that the contribution of CTAB was always more than that of SAIL. The results have been analysed on the basis of Rubingh, Clint and Motomura theory. Various mixed micellar parameters such as ideal cmc (cmc*), activity coefficients (f1 and f2), micellar mole fraction of CTAB in mixed and ideal state (X1mandX1ideal), interaction parameter (βm) and excess Gibbs free energy of micellization (ΔGex) have been calculated at temperatures of (298.15, 308.15 and 318.15) K. Mixed micellar parameters (cmc*, X1m, and ΔGex) reveal non-ideal behaviour of the mixed system and magnitude of interaction parameter (βm) becomes more negative in the presence of salt. 1H NMR shed light on the electrostatic interactions between CTAB and SAIL in mixed state.

Critical Micelle Concentrations of Sodium Dodecyl Sulfate and Cetyltrimethylammonium Bromide Mixtures in Binary Mixtures of Various Salts at Different Temperatures and Compositions

By conductivity method were examined the aggregation behavior of cationic amphiphile–cetyltrimethylammonium bromide (CTAB) and anionic amphiphile–sodium dodecyl sulfate (SDS) mixtures in binary mixtures of various salts. The values of critical micelle concentration (cmc) of SDS–CTAB mixtures lie between the cmc values of the pure amphiphiles. With temperature increasing the cmc values decrease first and then enhance with further rise of the temperature. The observed cmc of the SDS–CTAB mixed systems in attendance of binary mixture of salts was obviously less as compared to aqueous solution. The degree of counterion dissociation along with cmc value was utilized to evaluate different thermodynamic parameters. The values of interaction parameters and excess free energy were found to be negative in all cases. All results obtained reveal the strong interaction between the studied amphiphiles.

Interactions in mixed micellar systems comprising chiral cationic amino acid based and conventional anionic surfactants

The formation of mixed micelle in water between a chiral cationic amino acid based surfactant, l-alaninehydrochloride dodecylester (l-ADDE), and conventional anionic surfactants (AS), sodium decyl sulfate (SDS), sodium dodecyl sulfate (SDDS) and sodium dodecylbenzene sulfonate (SDBS), has been investigated by conductivity, density and dynamic light scattering (DLS) measurements at 25 °C. The critical micelle concentrations (CMC), degree of counterion dissociation (α) and standard Gibbs energy of micellization (ΔGmic°) have been determined for both pure and mixed systems, and the results have been compared with each other. Physicochemical parameters included the critical micelle concentration of ideal mixtures (CMCideal), the mole fraction of l-ADDE in ideal (XL−ADDEideal) and real mixed micelles (XL−ADDE), and interaction parameter (β) have been calculated by theoretical models to reveal the properties of mixed micelles. l-ADDE/SDS mixed system exhibited behavior changing from synergistic to antagonistic interactions with increasing l-ADDE concentration, whereas a reverse case was observed in l-ADDE/SDBS mixed system, i.e., from antagonistic to synergistic interactions. l-ADDE/SDDS mixed system showed antagonistic interactions over all the mole fraction range studied. The change of the apparent molal volume upon micellization (∆Vφmic) values determined from density measurements revealed that mixed micelles packed more tightly than their corresponding pure micelles. In addition, the sizes of the aggregates in binary mixed systems were found to be larger than those of the pure ones indicating the transformation from the small micelles to large aggregated structures. The increment in size of aggregates may be suggested with the vesicular structures.