Thermodynamics Of Micellization Research Articles

Thermodynamics of micellization of octyltrimethylammonium bromide in 1,2-propanediol-water mixtures at temperatures from (293.15 to 308.15) K

The micellar properties of octyltrimethylammonium bromide (C8TAB) in both water and aqueous solutions of 1,2-propanediol have been investigated using accurate measurements of density, sound velocity, and surface tension in the temperature range between 293.15 and 308.15 K. The critical micelle concentration, CMC, the ionization degree, β, the standard thermodynamic parameters of micellization: free energy, ΔmicG°, enthalpy, ΔmicH°, entropy, ΔmicS° and the free energy of transfer, ΔtrG°, of the surfactant octyltrimethylammonium bromide in both water and 1,2 propanediol aqueous solution were evaluated from the experimental results.The CMC of the surfactant increases as the concentration of 1,2-propanediol increases, while the temperature does not exert important changes within the range considered.The value of the micellization thermodynamic parameters suggests that adding 1,2-propanediol makes the micellization process less favorable.The thermodynamic functions of transfer were calculated. The values of the free energy of transfer are small and positive and increase as the diol concentration increases confirming that the transfer of the surfactant from the bulk into the micelle is less favorable.

Interaction, Surface Activity, and Application of Mixed Systems of Alcohol Ether Sulfate Anionic Surfactants with Multiple Ethylene Oxide Groups and Gemini Quaternary Ammonium Surfactant.

The surface activities and application properties for the mixtures of cationic surfactants tetramethylene-1,4-bis[N,N-bis(hydroxypropyl)-hexa/decyloxypropylammonium] bromide (GC10-P) and tetramethylene-1,4-bis[N,N-bis(hydroxyethyl)-hexa/decyloxypropylammonium] bromide (GC10-E) and anionic surfactant isomeric sodium fatty alcohol ether sulfates (iso-AE9S) were investigated using both the tensiometry and the conductometry. The interaction parameters and thermodynamic micellization parameters of GC10-P/iso-AE9S and GC10-E/iso-AE9S mixtures were evaluated by Clint-Rubingh and Motomura theoretical models. When the mole fraction of α1 for GC10-P/iso-AE9S mixed system was 0.2, the critical micelle concentration (CMC) reached a minimum of 1.61 × 10-4 mol/L, and the minimum critical micelle concentration of the GC10-E/iso-AE9S mixed system is 2.67 × 10-5 mol/L at α1 = 0.6. The CMC value of the mixed system is 1-2 orders of magnitude lower than that of any single component. The results indicate that the synergistic effects of the investigated mixed systems (evaluated by βm) are in order of GC10-P/iso-AE9S < GC10-E/iso-AE9S, with maximum βm values of -17.98 and -9.78, respectively. The change in zeta potential indicates that the poly(ethylene oxide) chain has weakened the charge density of the hydrophilic headgroup of the anionic surfactant. The interfacial tension at the oil-water interface in the mixed system of anionic/cationic surfactants is lower than that of any single component, exhibiting a higher interfacial activity. The mixed system exhibits a decreased contact angle and superior wetting ability over any single component, and it also enhances foam performance, emulsification performance, and degreasing performance.

Thermodynamics of doxorubicin - bile salt association: An investigation based on isothermal titration calorimetry

Association of doxorubicin (DOX), a positively charged anthracycline, with bile salts (sodium cholate, NaC; sodium deoxycholate, NaDC, and sodium taurodeoxy cholate, NaTDC) has been studied by isothermal titration calorimetry (ITC). These bile salts form micelles in physiological conditions, and subsequent micellization parameters vary in accordance to their hydrophobicity. In this study, we show that thermodynamics of micellization of bile salts can be modulated via incorporation of DOX and changes in solution temperature. DOX incorporation was accompanied with reduction in critical micelle concentration (CMC) of bile salts. This was mediated through expulsion of structured water from the hydrophobic part of bile salt, and it was verifiable from the appearance of additional thermodynamic events in demicellization process. Interestingly, free energy of bile salts increased upon adding DOX which is suggestive of loss in the spontaneity of their micellization following this association. We assert that micelle formation in case of bile salt – DOX complex may not have occurred instantly. Instead, it was preceded by a bile salt - DOX equilibrium as a result of changes in the interfacial characteristics of bile salts in question.

Physicochemical Properties of Cetrimonium Bromide in Electrolytes and Nonelectrolyte Environments

Background: The physicochemical properties, including the thermodynamics of micellization studies, received much attention. Cationic surfactant cetrimonium bromide (C16TABr) in electrolytes (sodium chloride and sodium salicylate) and nonelectrolyte (Ethylene glycol) in an aqueous solution were examined, and interesting results were obtained. The present investigation aims to identify a suitable combination of cationic surfactant cetrimonium bromide + electrolytes and nonelectrolytes having the ability to alter the size or shape of the micellar system using available methods. Methods: Surface tension, conductivity, viscosity, ultrasonic velocity, and dynamic light scattering (DLS) methods at different temperatures (303-323K) were used during the experimental research work. Results: The experimental results pointed out that the incorporation of electrolytes and nonelectrolyte into the cationic surfactant affects the physicochemical properties such as critical micelle concentration (CMC), surface tension (ST), degree of ionization (α), degree of counterion binding (β), standard Gibbs free energy of micellization (ΔGo m), standard entropy of micellization (ΔSo m), standard heat of micellization (ΔHo m), viscosities, and acoustic parameters. Dynamic light scattering (DLS) measurements reveal exciting facts related to the size and shape transformation of the mixed micellar assembly. Structure modification can be obtained by choosing right the combination of cationic surfactant cetrimonium bromide + electrolytes (sodium chloride and sodium salicylate) and nonelectrolyte (Ethylene glycol) ratio. Conclusion: It concluded that, over a threshold level, an electrolyte such as NaCl concentration causes the micelle size to rise. The entropy of micellization goes down when a structure-breaker (EG) is added to the water phase, and this is because the structure of the water is changed near hydrophobic groups. The physicochemical features of cetrimonium bromide (C16TABr) show unique behaviour under the influence of micelle-driven and micelle- forbidden systems.

An investigation on the hydrophobic binding stability of Azithromycin to the hydrocarbon chains of Tween: Based on micellization thermodynamics

Based on micellization thermodynamics, the difference in hydrophobic binding stability between Azithromycin and the hydrocarbon chain of Tween was investigated. Initially, the critical micelle concentration (CMC) of AZM-loaded Tween micelles was determined by measuring surface tension, followed by subsequent analysis and discussion of the associated parameters of micellization thermodynamics. The findings indicated that AZM-loaded Tween 20 and AZM-loaded Tween 80 micelles both exhibited a lower CMC value, enhanced stability at the air/water interface, and a more pronounced tendency towards micellization. This suggested that Azithromycin exhibited a stronger affinity towards the hydrophobic hydrocarbon chains of Tween 20 and Tween 80, leading to a more robust hydrophobic binding between them, thereby promoting the formation of AZM-loaded micelles. Subsequently, the transmittance, particle size, and in vitro release of each micelle system were assessed. The findings demonstrated that both AZM-loaded Tween 20 and AZM-loaded Tween 80 micelles exhibited excellent physical stability. Furthermore, in terms of antibacterial activity, AZM-loaded Tween 20 and AZM-loaded Tween 80 micelles exhibited stronger antibacterial efficacy. In summary, the variation in the hydrocarbon chain of Tween exerts an influence on the stability of the hydrophobic binding between Tween and Azithromycin, consequently impacting the pertinent attributes of drug-loaded micelles. This finding offers a valuable point of reference for the investigation of hydrophobic drug micelles in academic research.

Surface activity and micellization of streptomycin sulfate and diphenhydramine hydrochloride in the presence of alkali and alkaline earth metal chlorides

ABSTRACT The study investigated the surface tension of the surface-active drugs streptomycin sulfate and diphenhydramine hydrochloride using three uni-univalent and three bi-univalent electrolytes: NaCl, KCl, and RbCl (0.01 mol.kg−1), and MgCl2, CaCl2, and SrCl2 (0.002 mol.kg−1) over a temperature range of 298.15 to 313.15 K. Surface tension determination has proven instrumental in examining the micellization and surface-active properties of these drugs in the presence of specific electrolytes. The surface tension values of these drugs exhibit a decrease in magnitude with increasing drug concentration, particularly noticeable in streptomycin sulfate. This phenomenon can be elucidated by considering the delicate balance between hydrophobic and hydrophilic forces within the system. Additionally, the impact of the nature of metal halides and temperature on surface tension magnitude has been scrutinised, with interpretations focused on alterations in size. From surface tension values, the interfacial parameters, such as Γ max , A min , and π CMC were examined. The results indicate a strong affinity between drug-electrolyte molecules that reduces the surface tension values. The CMC relations govern the hydrophobic and hydrophilic interactions in the ternary system of water-drug-electrolyte. The thermodynamics of micellization explains the work done for micellization and illuminates the surface and bulk properties of drugs.

Synergistic improvement of the fine size coal dewatering performance by using binary surfactant mixtures

In this study, gemini surfactants and binary surfactant mixtures were used in order to enhance the dewatering performance of fine size coal particles. Compared to three single gemini surfactants, binary surfactant mixtures presented a better dewatering performance of fine size coal particles, especially the binary surfactant mixture composed of Gemini − 1 surfactant and sodium dodecyl benzene sulfonate (SDBS). Meanwhile, the binary surfactant mixture composed of Gemini − 1 surfactant and sodium dodecyl sulfonate (SDS) was further used in the experimental test as a comparison and showed better dewatering performance than that of the binary surfactant mixture composed of Gemini − 1 surfactant and SDBS. The lowest cake moisture content (20.72 %) was gained when the dosage of Gemini − 1 surfactant and SDS was 400 g/t at the molar ratio of 6 to 7. Surface functional groups of the prepared coal samples were characterized by a Fourier transform infrared spectroscopy (FTIR). Wetting heat values of coal samples before and after adsorbing surfactants were measured by a microcalorimeter. The adsorption capacity of surfactant on coal surface was investigated for studying the difference between three single surfactants and the binary surfactant mixture. Intermolecular interaction calculation and thermodynamics of micellization for the judgment of synergistic effect indicated that the synergistic interaction was formed in the binary surfactant mixture and the binary surfactant mixture of Gemini − 1 surfactant and SDS showed a stronger synergistic interaction. A possible hydrophobic mechanism was supposed that the water molecules were displaced by the binary surfactant mixture for the improvement of hydrophobicity of coal particle surface.

Chemico-Physical Properties of Some 1,1'-Bis-alkyl-2,2'-hexane-1,6-diyl-bispyridinium Chlorides Hydrogenated and Partially Fluorinated for Gene Delivery.

The development of very efficient and safe non-viral vectors, constituted mainly by cationic lipids bearing multiple charges, is a landmark for in vivo gene-based medicine. To understand the effect of the hydrophobic chain's length, we here report the synthesis, and the chemico-physical and biological characterization, of a new term of the homologous series of hydrogenated gemini bispyridinium surfactants, the 1,1'-bis-dodecyl-2,2'-hexane-1,6-diyl-bispyridinium chloride (GP12_6). Moreover, we have collected and compared the thermodynamic micellization parameters (cmc, changes in enthalpy, free energy, and entropy of micellization) obtained by isothermal titration calorimetry (ITC) experiments for hydrogenated surfactants GP12_6 and GP16_6, and for the partially fluorinated ones, FGPn (where n is the spacer length). The data obtained for GP12_6 by EMSA, MTT, transient transfection assays, and AFM imaging show that in this class of compounds, the gene delivery ability strictly depends on the spacer length but barely on the hydrophobic tail length. CD spectra have been shown to be a useful tool to verify the formation of lipoplexes due to the presence of a "tail" in the 288-320 nm region attributed to a chiroptical feature named ψ-phase. Ellipsometric measurements suggest that FGP6 and FGP8 (showing a very interesting gene delivery activity, when formulated with DOPE) act in a very similar way, and dissimilar from FGP4, exactly as in the case of transfection, and confirm the hypothesis suggested by previously obtained thermodynamic data about the requirement of a proper length of the spacer to allow the molecule to form a sort of molecular tong able to intercalate DNA.

Micellization thermodynamics, interfacial behavior, salt-resistance and wettability alteration of gemini hybrid fluorinated surfactant

A new Gemini hybrid surfactant DFCS was prepared to improve salt resistance and interface activity of fluorinated surfactants. This surfactant was expected to be used as a cleanup additive in fracturing and an active agent in water flooding for shale and superlow-permeability sandstone reservoirs. At high salinities, it displayed lower interface tensions than current fluorinated surfactants as well as the obvious non-wettability of water on glass, and the modified natural sandstone surface using DFCS was close to intermediately wetting for the water and oil phases. Also, DFCS exhibited good temperature resistance, and the surface and interface tensions reduced markedly with the temperature below 70 ℃ in water and brine. For DFCS, the molecular area was large, e.g. ACMC= 129.61 Å2 at 30 °C; the micelle formation was entropy-driven, and the spontaneity was stronger than that of reported hybrid surfactants with single −SO3− ion. The TEM observation showed that the diameters of mono-molecules and micelles were respectively 3–5 and 20–30 nm for 1.9 g/L (CMC) DFCS in water. It was found by the UV data that the non-polarity in micellar micro-domains was visibly weaker for Gemini hybrid surfactants in comparison to hydrocarbon surfactants and that salt hardly influenced the sizes of their micelles, resulting in good salt resistance.

Dimethyl sulfoxide fosters larger micelles of docusate sodium in the mixed solutions with water

Docusate sodium also referred to as sodium bis(2-ethylhexyl)sulfosuccinate and dioctyl sulfosuccinate sodium (AOT) represents a green salt with proven potential across pharmacy, biology, and medicine. Physicochemical understanding of its inherent structural patterns, transport properties, and phase behavior in solutions is a challenging but essential endeavor. We hereby report conductometry, surface tension, density, and dynamic light scattering measurements of AOT in the dimethyl sulfoxide (DMSO)-water mixtures. The ab initio simulations are used to shed light on the electron density distributions and non-covalent interactions in the systems of our interest. We determine critical micelle concentration (CMC) and thermodynamic parameters of micellization (Gibbs free energy, enthalpy, and entropy) using the conductometry data at 298.15, 303.15, 308.15, 313.15, and 318.15 K. The CMC of AOT increases as DMSO mole fraction in the DMSO-water mixture increases. Negative free energies of micellization are observed over the entire investigated temperature range. Furthermore, higher contents of DMSO foster micellization gradually.The high contents of DMSO (X > 0.3) in the DMSO-water mixtures lead to abrupt changes in CMC and thermodynamics of AOT micellization. We link such changes to the formation of the DMSO self-associates and the associated structural changes in the liquid phase. The dynamic light scattering measurements reveal that larger micellar agglomerates and multilamellar AOT vesicles emerge at high DMSO fractions. The reported data fosters the thoughtful design of practically important systems in medicine.

An empirical model to represent the CMC behavior of aqueous solutions of homologous series of nonionic surfactants, related to its chemical constitution

• The Critical Micelle Concentration (CMC) is a fundamental property of surfactants. • An empirical model is presented based on the thermodynamics of micellization of a given homologous series of surfactants. • The reason for the observed increase and decrease in CMC value is explained. • The proposed model is compared with other empirical models and its quality to estimate the CMC is superior. Critical Micelle Concentration (CMC) is a fundamental property of surfactants in (aqueous) solution. The importance of defining the CMC of an aqueous surfactant solution is related to the different behavior and performance of the given system below and above its CMC, which has impact on the usage of this type of systems for different industrial applications. In this work, an empirical model is presented, based on the fundamental equation for the thermodynamics of micellization of a given homologous series of surfactants with the same chemical nature, to estimate the corresponding CMC. This simple model contains three adjustable parameters and allows predicting the log[CMC] of the nonionic surfactants polyoxyethylene alkyl ethers (C n E m ) in aqueous solution. The analysis of the three parameters showed that the hydrophobic characteristics play the major role in micelle formation. The polarity of the molecules is also important, but its effect is less pronounced. The proposed model is compared with other empirical models and its quality to estimate the CMC is superior.

Thermodynamics of pluronic 103 micellization in mannitol solution: Analyses based on isothermal titration calorimetry

This study describes the effect of sugar incorporation upon micellization behaviour of pluronic 103 (P103), a linear triblock copolymer. Mannitol (MTL) was used as a sugar and its effect was investigated over a concentration range of 0.1–1 M. Our interpretations on changes in the thermodynamics of P103 micellization are based on isothermal titration calorimetry (ITC) experiments. Thermodynamic parameters were calculated after plotting the enthalpy against temperature and MTL concentration. The data were acquired at six temperatures between 302.5 and 312.5 K. A significant reduction in CMC was witnessed following increase in solution temperature and MTL incorporation. We show that enthalpy barrier of micellization reduced in the presence of MTL. The data of Gibb’s free energy of micellization (ΔGºmic) exhibited a steady decline during increase in MTL concentration. These changes were attributed to modulation of water structures in the microenvironment of micelle interface. Linearity of enthalpy-entropy compensation underscored the role of temperature in regulating copolymer-solvent interactions.

Facile synthesis of Fe3O4/Sio2/Cu nanoparticles: investigation of physicochemical attributes of interaction in cationic micellar media and photo-antibacterial impact

Solubilization of core-shell magnetic nanoparticles has gained new popularity as a versatile partitioning method with the recent growth in nanotechnology and related biotechnology applications. In this sense, Fe3O4/SiO2/Cu nanoparticles (NPs) were designed and characterized by various techniques such as Ultra-violet visible (UV-vis), Fourier transforms infrared (FTIR), X-ray diffractometry (XRD), scanning and transmission electron microscopy (SEM &amp; TEM), energy dispersive X-ray (EDX) and thermogravimetric (TGA) analyses. The size determined by TEM analysis of Fe3O4/SiO2/Cu NPs was found in the range of 24 nm. The diffractometer results verified the impurity-free synthesis of the desired nanoparticles. Micellar solubilization and thermodynamics of micellization were determined correspondingly using a UV-Vis spectrophotometer and conductometer. The thermodynamics of micellization in terms of enthalpy, entropy and standard Gibb’s free energy was determined using electrical conductometry. The solubilization parameters viz. partition constant (Kc), binding constant (Kb), partition coefficient (Kx), and the corresponding Gibb’s free energies were estimated from the absorption spectroscopic analysis. The experimental outcomes and their computation revealed the rise in the critical micelle concentration of CTAB due to the incorporation of the nanoparticles with the micelles. Moreover, the photo-antibacterial activity of the nanoparticles in the bacteria culture environment showed effectiveness in comparison to the control group.

Thermodynamics of micellization and oil solubilization in block copolymers P85

Thermodynamics of micellization and oil solubilization in block copolymers P85

Micellization and thermodynamics study of ester functionalized picoline-based ionic liquid surfactants in water.

A novel series of picoline-based ionic liquid surfactants, N-alkyoxycarbonyl-3-picoline bromides [CnEmpy][Br] (n = 10, 12, 14), have been synthesized. The thermal stability, aggregation behavior and surface activity of the synthetic ionic liquid surfactants were investigated systematically though a series of methods, such as thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), tensiometry and conductivity. The thermodynamics of micellization of the ionic liquid surfactants solution were studied by using the conductivity method in the temperature range 278.15–318.15 K. The surface activity parameters and thermodynamics parameters were derived, respectively. The enthalpy–entropy compensation effect was further discussed by using relative thermodynamics parameters. It was found that the [CnEmpy][Br] have moderate surface activity, and their critical micelle concentration (CMC) decreased with the ester-functionalized chain length and exhibited a U-shape with temperature. The calculation results of the thermodynamic parameters showed that the micellization processes of [CnEmpy][Br] were spontaneous, endothermic at low temperature and exothermic at higher temperature.

Effects of Selected Metal Chlorides on the Micellization Parameters of Cetrimonium Bromide at Different Temperatures

The pre-modification of surfactant counterions using transition metal salts provides a means to activate the interface using corresponding properties of metal ions. In this work, a cationic surfactant cetyltrimethylammonium bromide (CTAB) was modified by pre-mixing metal chlorides (FeCl3, CuCl2 and ZnCl2) and CTAB in 1:1 molar ratio using methanol as solvent. As a result, FeCl3, CuCl2 and ZnCl2 were added as [FeCl3Br]-1, [CuCl2Br]-1 and [ZnCl2Br]-1 respectively acting as counter anions (CAs) instead of bromide anion. Hence CTAB was called CTAF, CTAC and CTAZ in order of added CAs i.e., [FeCl3Br]-1, [CuCl2Br]-1 and [ZnCl2Br]-1 respectively. The effect of these metal chlorides on the micellar behaviour of CTAB was investigated using conductivities of their different solutions. Furthermore, the critical micelle concentration (CMC) as well as the degree of counterion binding were considered at 25.0, 30.0, 35.0, 40.0 and 45.0 and#176;C 0.1 and#176;C. The analysis of results revealed that incorporation of metal cations reduces the CMC values in the order CTAF CTAZ CTAC CTAB. Change in entropy (S), enthalpy (H) and free energy (G) were calculated to understand the thermodynamics of micellization under the circumstances. The aim of this study is to improve the understanding regarding the presence of transition metals in micellization process as well as the possibility of their interactions with Bromide counterions and possibility of the formation of complex counter-anions.

Development and optimization of aprepitant/HS15/TW80 composite system: Based on micellization thermodynamics

In this paper, based on the concept of micellization thermodynamics, aprepitant/HS15/TW80 composite system was developed. The interface and micellization behavior of binary and ternary mixtures of Polyoxyl 15 Hydroxystearate (HS15), Polysorbate 80 (TW80) and aprepitant (APPT) have been studied in detail. Surface tension technology was used to study the effects of different HS15/TW80 ratios, temperature, stirring time, pH, and solvents on the thermodynamic behavior of the aprepitant (APPT) mixed micellar system during the preparation process. Air/water interface parameters such as maximum surface excess concentration (Tmax), effectiveness of surface tension reduction (Πcmc), minimum area per surfactant molecule (Amin) and thermodynamic parameters for binary and ternary systems were computed and discussed one by one. The ΔGm and ΔGads values for every studied solution were negative, indicating that micellization, as well as adsorption processes, were spontaneous. Compared with the binary system, the ternary systems were more effective in reducing the critical micelle concentration (CMC) of the solution and promoting the formation of micelles. During the preparation process, when the surfactant ratio in the solution was HS15/TW80 = 1, the temperature was 308.15 K, the stirring time was 4 h, the pH value was 5.00, and the solvent was 0.5% glucose solution, APPT/ HS15/TW80 mixed micellar solution with excellent thermodynamic and physical stability can be obtained. In addition, the results of transmittance and insoluble particles further verified the stability of the composite micelle system. The excellent drug loading characteristics of the new APPT/HS15/TW80 complex micelle system were proved by drug loading experiments. In this study, a stable APPT/HS15/TW80 composite system was established by the theory of micellization thermodynamics.

EFFECTS OF POLYMER CONCENTRATION AND TEMPERATURE ON MICELLIZATION OF CETYLTRIMETHYLAMMNIUM BROMIDE (CTAB) IN AQUEOUS PVP-CTAB MIXED SYSTEM

Polymeric micelles supply an environment, which can be cautiously regulated for drug delivery. The self-assembly of polymeric micellization is dynamic. Micellization thermodynamic describes how the system defines the formation of micelles. The present study enables the micellization behavior of the surfactants in the presence of polymer to be examined by conductometric and tensiometric methods. The effects of polymer concentration and temperature on the micellization thermodynamics of a neutral soluble polymer and cationic cetyltrimethylammomium bromide (CTAB) surfactant mixture in aqueous medium were investigated. To examine polymer-surfactant interaction, critical micellar concentration (CMC) and thermodynamic parameters such as standard free energy ∆G, enthalpy ∆H and entropy ∆S are calculated by using a pseudo-phase model. Based on CMC, ΔG, ΔH and ΔH, the dependence of the compensation temperature on the polymer effect is discussed. This advanced work to understand micelle stability and compatibility can be comprehensively feasible in polymeric systems.

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.

Studies of thermodynamics of micellization and pattern of self-association of decyltrimethylammonium bromide in aqueous solutions at 298.15 K

Using recently reported density, thermal coefficient of expansion and internal pressure data along with the literature osmotic coefficient and enthalpy data and adopting Mass–action model, the properties of decyltrimethylammonium bromide (C10TAB) in water are studied at 298.15 K. The number density, aggregation number, equilibrium constant, standard free energy changes due to micellization, standard entropy changes due to micellization and mean ionic activity coefficient are calculated in pre–micellar and post–micellar regions of concentration assuming that the cationic surfactant C10TAB is fully dissociated in water. Characteristic pattern of association are examined through the models/concepts developed by Tanford, Mukerjee as well as by O. P. Ts’o and noted that hydrophobic interactions between the non–polar chains and water structural effects (in the form of ion–solvent and ion–ion interactions) govern the equilibrium properties of such solutions. The critical micelle concentration (cmc) value and aggregation number value agree with the literature data. It has been observed that aggregation number value decreases slightly, equilibrium constant value goes through a minimum, standard free energy changes due to micellization parameter go through a maximum while positive magnitude of entropy changes due to micellization are observed as a function of concentration of C10TAB. The variation of mean ionic activity coefficient of the salt ions with concentration indicates deviation from ideal–associative solution behaviour. All these results are interpreted on the basis of monomer–micelle equilibria existing in solution phase, affecting the solution properties through electrostatic, hydrophobic solvation and hydrophobic interaction effects.