Thermodynamics Of Micellization Research Articles

An improvement of thermodynamic micellization model for prediction of asphaltene precipitation during gas injection in heavy crude

Thermodynamic micellization model is known as an appropriate approach for prediction of asphaltene precipitation. However, the reliability (i.e. accuracy) of this model for whole range of pressure or injected gas mole percent must be checked. In practice, the accuracy can be improved by using a suitable characterization method. In this research, a computer code for implementing the thermodynamic micellization model has been developed. Having used this program, we make the prediction of asphaltene precipitation by using data reported in the literature as well as the experimental data obtained from high pressure, high temperature asphaltene precipitation experiments under gas injection conditions. An enhancement to the thermodynamic micellization model has been proposed by applying the characterization method taken from the thermodynamic solid model. This new approach introduces a new matching parameter representing the interaction coefficients between the asphaltene component and light hydrocarbon components. Sensitivity analysis has emphasized that the thermodynamic micellization model is highly sensitive to this new matching parameter, the resin interaction energy parameter (Δ U r ), the interfacial tension between the asphaltene micellar core and the crude ( σ 0), and the concentration of asphaltene monomers in the crude which is in equilibrium with the pure solid asphaltene phase ( X a 1 o n s ) . Finally, the predictions obtained from this approach under gas/solvent injection conditions, resulted in a good agreement with experimental data which shows a significant improvement in comparison to the other matches in the available literature.

Influence of the alkyl chain length, temperature, and added salt on the thermodynamics of micellization: Alkyltrimethylammonium chlorides in NaCl aqueous solutions

The thermodynamics of micelle formation of the cationic surfactants decyltrimethylammonium chloride (DeTAC) and tetradecyltrimethylammonium chloride (TTAC) in water and aqueous NaCl solutions have been investigated. Isothermal titration calorimetry (ITC) was used to study the effect of added salt on the critical micelle concentration, cmc, and enthalpy of micellization, Δ mic H ∘ , between the temperatures (278.15 and 328.15) K. From the temperature dependence of Δ mic H ∘ , the heat capacities of micellization, Δ mic c p ∘ , were determined. The results obtained are compared with reported data for dodecyltrimethylammonium chloride (DTAC). The values of Δ mic c p ∘ are negative for all surfactants in all solvents relating to the removal of water accessible non-polar surfaces also in the presence of excess counterions. The temperature dependence of Δ mic c p ∘ is evident at DeTAC, leading to the assumption that, especially at high temperatures, the non-polar parts of surfactant molecules are still in perceivable contact with water.

Thermodynamics of micellization of cationic surfactants based on O-alkyl and O-perfluoro- N, N′-diisopropylisourea: Effect of the counter ion nature

A thermodynamic study on the micellization process of two series of cationic surfactants, viz. the O-dodecyl- N, N′-diisopropylisourea hydrochloride, hydrobromide, and hydroiodide and the O-tridecafluorooctyl- N, N′-diisopropylisourea hydrochloride, and hydrobromide, is reported. In order to explain the effect of the counter ion nature in the micellization process, thermodynamic parameters to include the standard free energy ( Δ G mic ∘ ), enthalpy ( Δ H mic ∘ ), entropy ( Δ S mic ∘ ), and heat capacity ( Δ C p,mic ∘ ) of micellization have been discussed. These parameters are evaluated from the variation of the critical micelle concentration (CMC) with temperature by fitting these values to expressions derived on the basis of a micellization thermodynamic model. The heat capacities of micellization ( Δ C p,mic ∘ ) were determined from the temperature dependence of Δ H mic ∘ . For both surfactant series, the free energy of micellization is weakly temperature dependent and becomes more negative with increasing the size of the counter ion, indicating a more favored micellization. The enthalpy and entropy of micellization decrease strongly with increasing temperature. The heat capacities of micellization ( Δ C p,mic ∘ ) were found to be negative. The enthalpy–entropy compensation phenomenon was observed for all the surfactants studied.

Thermodynamics of micellization of some non-ionic surfactants in mixed solvents.

Abstract The thermodynamics of micellization of three non-ionic surfactants in mixed solvents are reported. The contribution of the alkyl chains of the surfactant molecules to micellization is estimated from solubility data.

Prediction of the micellar molecular weight and thermodynamics of micellization of mixtures of alkyltrimethylammonium salts

Journal Article Prediction of the micellar molecular weight and thermodynamics of micellization of mixtures of alkyltrimethylammonium salts Get access B W BARRY, B W BARRY School of Pharmacy, Portsmouth Polytechnic, Park Road, Portsmouth, PO1 2QQ, UK Search for other works by this author on: Oxford Academic Google Scholar G F J RUSSELL G F J RUSSELL School of Pharmacy, Portsmouth Polytechnic, Park Road, Portsmouth, PO1 2QQ, UK Search for other works by this author on: Oxford Academic Google Scholar Journal of Pharmacy and Pharmacology, Volume 23, Issue Supplement_1, December 1971, Pages 241S–242S, https://doi.org/10.1111/j.2042-7158.1971.tb08829.x Published: 12 April 2011

Thermodynamics of Surfactant Micellization in Presence of Benzamide Derivatives

Aggregations of cationic CTAB and anionic SDS surfactants induced by constant concentrations of N-m-tolylbenzamide (NTB) and N-(4-methoxyphenyl) benzamide (MPB) additives in aqueous solution were investigated by measuring their conductance as a function of surfactant concentration below and above their critical micelle concentration (CMC) at a temperature range of 25 to 50°C. Aggregations took place at surfactant concentrations far below their normal CMC in presence of additives. Rapid micellization in aqueous solution is the result of both hydrophobic and electrostatic interactions. The effect of additives on surfactants CMC and thermodynamics parameters of micellization were determined in this study.

Prediction of Asphaltene Precipitation During Solvent/CO2 Injection Conditions: A Comparative Study on Thermodynamic Micellization Model With a Different Characterization Approach and Solid Model

Summary There are different thermodynamic models that have been applied for modelling of asphaltene precipitation caused by various reasons, such as solvent/CO2 injection and pressure depletion. In this work, two computer codes based on two different asphaltene precipitation thermodynamic models--the first being the thermodynamic micellization model with a different characterization approach and the second being the solid model--have been developed and used for predicting asphaltene precipitation data reported in the literature as well as in the obtained data for Sarvak reservoir crude, which is one of the most potentially problematic Iranian heavy oil reserves under gas injection conditions. For the thermodynamic micellization model, a new approach was obtained by applying the characterization method taken from the thermodynamic solid model for oil component characterization. This new approach introduced a new matching parameter to the model, representing the interaction coefficients between asphaltene components and light hydrocarbon components, which resulted in a significant improvement in the thermodynamic micellization model predictions of asphaltene precipitation data under gas injection conditions. The model parameters obtained from a sensitivity analysis were applied in both thermodynamic models, and the experimental data of asphaltene precipitation were predicted. The asphaltene precipitation predictions from the solid model showed good agreement with the data taken under gas/solvent injection conditions. Especially for the trend of the titration curve after the peak point, reasonable agreements were observed which could rarely be found in the available literature. It has been observed that although the thermodynamic micellization model with a different characterization approach is more complex than the solid model, it is able to predict the trends of asphaltene precipitation curves for gas titration conditions reasonably well. Also, its predictions matched well with more experimental data points in comparison to the solid model predictions.

Synthesis, structure, CMC values, thermodynamics of micellization, steady-state photolysis and biological activities of hexadecylamine cobalt(III) dimethyl glyoximato complexes

Metallosurfactant complexes of the type trans- [Co(DH)2(HA)X], where DH = Dimethyl glyoxime, HA = Hexadecyl amine and X = Cl−, Br−, I−, N3−, NO2− or SCN−, were synthesized and characterized by physico-chemical and spectroscopic methods. In addition, the single crystal X-ray structure of the ionic complex trans-[Co(DH)2(HA)2][Co(DH)2(I)2)] is presented. The critical micelle concentration values of the complexes in ethanol were obtained by measuring the absorption at 290 nm. Specific conductivity data (at 303–313 K) served for the evaluation of the thermodynamics of micellization \( \left( {\Updelta G^{0}_{{{\text{m}}}}, \Updelta H^{0}_{{{\text{m}}}}, \Updelta S^{0}_{\text{m}} } \right) \). Steady-state photolysis, cyclic voltammetry and biological activities of the complexes were studied. The compounds were tested for antimicrobial activity.

Synthesis, Characterization and CMC Determination of some Double-Chain Surfactant-Cobalt(III) Complexes

Abstract Some new surfactant-cobalt(III) complex ions of the type, cis-[Co(X)2(C14H29NH2)2]3+ (where X = ethylenediamine or 2,2’ bipyridyl or 1,10-phenanthroline) and cis-α-[Co(trien)(C14H29NH2)2]3+ were synthesized and characterized by IR, NMR, UV-Visible electronic absorption spectra, elemental analysis and metal analysis. The critical micelle concentration (CMC) values of these surfactant-cobalt(III) complexes in aqueous solution were obtained from conductance measurements. Specific conductivity data (at 298, 308 and 318 K) served for the evaluation of temperature-dependent CMC and the thermodynamics of micellization (ΔG0 m, ΔH0 m, ΔS0 m).

Micellization of Cetyldiethylethanolammonium Bromide in Mixed Aqueous Organic Solvents

The micellization of cetyldiethylethanolammonium bromide has been studied in binary aqueous mixtures of dimethyl sulfoxide, dimethyl formamide, acetonitrile, methanol and tetrahydrofuran at 298–320 K using conductometric technique. Thermodynamics of micellization, i.e., Gibbs free energy (), enthalpy (), and entropy (), have been obtained from temperature dependence of critical micelle concentration (CMC). The CMC and degree of counterion ionization (α), values increases with increase in temperature and volume percentage of the aqueous-organic solvent mixtures.

Thermodynamic of micelle formation of nonlinear block co-polymer Tetronic ® T904 in aqueous salt solution

Calorimetric and spectroscopic studies have been carried out to investigate the thermodynamics of temperature-induced micellization of Tetronic ® T904 [(EO 15PO 17) 2NCH 2CH 2N (PO 17EO 15) 2] in aqueous salt solutions. High-sensitivity differential scanning calorimetry (HSDSC), nuclear magnetic resonance (NMR) and Fourier transfer infrared (FTIR) measurements were used to evaluate the critical micellization temperature (CMT). The critical micellization concentration (CMC) and the thermodynamic parameters of micelle formations, namely enthalpy (Δ H mic), Gibbs energy (Δ G mic), and entropy (Δ S mic) of micellization were determined as a function of temperature and salt concentration using isothermal calorimetry (ITC). These measurements indicated spontaneous micellization with substantial enthalpy–entropy compensation of T904 micellization.

Thermodynamics of Micellization and Conductance Behavior of Uranyl Soap Solutions

Abstract The conductance results showed that uranyl soaps behave as weak electrolyte in dilute solution of N,N-dimethylformamide (DMF) at various temperatures below the critical micelle concentration, indicating that Debye–Hückel–Onsager's equation is not applicable to these soaps solutions. The value of critical micelle concentration decreases with increasing chain length of the soap and increasing temperature. The results were used to evaluate various thermodynamic parameters for both dissociation and association processes and may be satisfactorily explained in the light of phase separation model. The results show that the dissociation process of these soaps was found to be endothermic while micellization is exothermic in nature.

Alkyl Propoxy Ethoxylate “Graded” Surfactants: Micelle Formation and Structure in Aqueous Solutions

The self-assembly of alkyl propoxy ethoxylate surfactants in aqueous solutions has been investigated with a focus on the (i) thermodynamics of micellization (critical micellization concentration; free energy, enthalpy, and entropy of micellization) and (ii) structure of the micelles (overall shape and size; local environment in the micelle core and corona) as affected by the surfactant composition (variation of degree of ethoxylation). The various results are compared to those for alkyl ethoxylate and poly(ethylene oxide)-b-poly(propylene oxide) amphiphiles with the aim to elucidate the role of the middle, propoxy, block in the novel alkyl propoxy ethoxylate surfactants which exhibit a "graded" hydrophobic-hydrophilic character.

Surface Activity, Thermodynamics of Micellization and Adsorption Properties of Quaternary Salts Based on Ethanolamines and Decyl Bromide

AbstractThe surface‐active properties of ionic‐liquid type salts synthesized by the interaction of ethanolamines and decyl bromide have been studied. Surface tension as a function of concentration of the surfactant in aqueous solution was measured at 10, 20, 30 and 40 °C using a drop volume stalagmometer. From these measurements, the maximum surface excess concentration and the minimum area per molecule at the aqueous solution/air interface, the critical micelle concentration (CMC), the surface pressure at the CMC, and the standard thermodynamic parameters of adsorption and micellization were calculated. The structural effects on adsorption, micellization, and the effectiveness of surface tension reduction are discussed in terms of these parameters.

Thermodynamics of Micellization of Nonionic Surfactant Tween‐40 in Presence of Additive Chloramine‐T Using Clouding Phenomenon

The phenomenon of solubilization of nonionic surfactant Tween‐40 has been studied through the influence of additive chloramine‐T in aqueous medium by measuring the cloud points (CP) of the pure surfactant and with chloramine‐T. The CP of pure surfactant was found to be increased with increasing concentration of Tween‐40. The CP of mixed system shows increasing trends with increased chloramine‐T. This is mainly due to increased micelle concentrations. The influence of chloramine‐T on the cloud point of Tween‐40 is a clear indication that the phenomenon of clouding is associated with the different micelles coalescing. Considering cloud point as threshold temperature of the solubility, the thermodynamic parameters of clouding process (ΔG0cl, ΔH0cl and ΔS0cl) have been evaluated using “Phase Separation Model”. The phase separation results from micelle‐micelle interaction. It was found that the overall clouding process was exothermic and ΔH0cl > TΔS0cl indicating that the process of clouding was guided by both enthalpy and entropy. This work supports the conjecture that the clouding is critical phenomenon rather than the growth of micelles. Findings of the present work supports to made the probable evidence of electrolyte‐surfactant interactions in aqueous medium.

Synthesis, characterization, critical micelle concentration determination, and antimicrobial studies of some complexes of chromium(III) metallosurfactants

Surface active mixed-ligand complexes of Cr(III) containing chelating ligands, namely ethylenediamine (en), triethylenetetramine (trien), 2,2-bipyridine (bpy), and 1,10-phenanthroline (phen) with different axial amine ligands (dodecylamine or cetylamine) were synthesized and characterized by UV–Vis, infrared, and NMR spectroscopies and elemental analysis. The magnetic moments (3.6–3.8 B.M.) are close to the spin-only value for a d3 Cr(III) in octahedral symmetry. The critical micelle concentration values of these surfactant metal complexes in aqueous solution were determined as a function of temperature using conductometric technique. Thermodynamics of micellization (, and ) were evaluated. Dodecyl/cetylamine metallosurfactants obtained were tested for antibacterial and antifungal activities having good activities.

Studies on the Reaction Kinetics and Mechanism of Iron(II) Reduction of the cis-Halogeno(cetylamine)bis(ethylenediamine)cobalt(III) Complex Ion in Aqueous Perchlorate Medium

The electron-transfer kinetics of the ionic surfactant complex cis-chloro/bromo(cetylamine)bis(ethylenediamine)cobalt(III) by iron(II) in aqueous perchlorate medium at μ=1.0 mol⋅dm−3 ionic strength have been studied at 303, 308 and 313 K by spectrophotometry under pseudo-first-order conditions using an excess of the reductant. The effects of [H+], ionic strength and [Fe2+] on the rate were determined. The reaction was found to be second order and showed to be independence of the acid concentration in the range [H+]=0.05–0.25 mol⋅dm−3. The second order rate constant increased with surfactant–cobalt(III) concentration and the occurrence of aggregation of the complex itself altered the reaction rate. Activation and thermodynamic parameters have been computed. It is suggested that the reaction of Fe2+(aq) with the cobal (III) complex proceeds by an inner-sphere mechanism. The critical micelle concentration (CMC) values of these surfactant–metal complexes were obtained in aqueous solution from conductance measurements. Specific conductivity data (at 303, 308 and 313 K) served for the evaluation of the temperature-dependence of the critical micelle concentration (CMC) and the thermodynamics of micellization (ΔGmo,ΔHmo and ΔSmo).

Metallosurfactant Schiff base cobalt(III) coordination complexes. Synthesis, characterization, determination of CMC values and biological activities

Twelve surfactant Schiff base ligands were synthesized from salicylaldehyde and its chloro-, bromo- and methoxy- derivatives by condensation with long-chain aliphatic primary amines, and a number of mixed ligand cobalt(III) surfactant Schiff base coordination complexes of the type [Co(trien)A]2+ were synthesized from the corresponding dihalogeno complexes by ligand substitution. The Schiff bases and their complexes were characterized by physico-chemical and spectroscopic methods. The complexes form foams in aqueous solution upon shaking. The critical micelle concentration (CMC) values of the complexes in aqueous solution were obtained from conductance measurements. Specific conductivity data (at 303–323 K) served for the evaluation of the thermodynamics of micellization (\( \Updelta G_{\text{m}}^{0} \), \( \Updelta H_{\text{m}}^{0} \), \( \Updelta S_{\text{m}}^{0} \)). The complexes were tested for its antimicrobial activity.

Energitics of micellizaion of sodium n-dodecyl sulfate at physiological conditions using isothermal titration calorimetry

The micellization characteristics of sodium n-dodecyl sulfate (SDS) have been investigated by microcalorimetric technique at conditions close to the physiological ones. The thermodynamics of micellization were studied at 20, 25, 30, 35 and 40 °C in 50 mM HEPES buffer, pH 7.4 and 160 mM NaCl using isothermal titration calorimetric (ITC) technique. The calorimeter can operate in a stepwise addition mode, providing an excellent method of determination of critical micelle concentration (CMC) and enthalpy of demicellization (and hence micellization). It can as well distinguish between aggregating and non-aggregating amphiphiles (solutes) in solution. The dilution enthalpy (∆H dil) was calculated and graphed versus concentration in order to determine the micellization enthalpy (∆H mic) and CMC. In addition to the CMC and ∆H mic, the effective micellar charge fraction (α) of the ionic surfactant micellization process can also be determined from ITC curves. The Gibbs free energy of the micellization (∆G mic), entropy of the micellization (∆S mic), and specific heat capacity of the micellization (∆C P,mic) process have been evaluated by the direct calorimetric method (mass-action model) as well as by the indirect method of van’t Hoff by processing the CMC and α results of microcalorimetry at different temperatures. The differences of the results obtained by these two procedures have been discussed. The presence of NaCl (160 mM) in the solutions decreased the CMC of SDS. The enthalpy changes associated with micelle dissociation were temperature-dependent, indicating the importance of hydrophobic interactions. The ∆G mic was found to be negative, implying, as expected, that micellization occurs spontaneously once the CMC has been reached. The values of ∆G mic were found to become more negative with increasing temperature and the ∆S mic was found to decrease with increasing temperature in both models.

Thermodynamics of Micellization of Aqueous Solutions of Binary Mixtures of Two Anionic Surfactants

The thermodynamics of micellization of mixed anionic/anionic surfactant solutions, that is, sodium dodecyl sulfate (SDDS) and sodium decyl sulfate (SDS), have been studied by surface tension, density, and conductivity measurements. The obtained results indicate that the values of critical micelle concentration strongly depend on the composition of the mixture and that the mole fraction of surfactants in the mixed micelle calculated on the basis of Rosen and Villeneuve approaches are different from those in the bulk phase. The small negative deviation from the linear relationship between the critical micelle concentrations and composition of SDDS and SDS mixtures in the bulk phase, the values of the molecular interaction parameters, activity coefficients, and the excess Gibbs energy of mixed micelle formation calculated on the basis of Rosen and Villeneuve approaches and calculations based on the MT theory of Blankschtein proved that there is synergism in mixed micelle formation of aqueous solutions of SDDS and SDS. It was also found that the values of the standard Gibbs energy of micellization for the mixture of these two surfactants which confirm the synergetic effect can be predicted on the basis of the proposed equations which include the values of the mole fraction of surfactant in the mixed micelle and excess Gibbs energy of micellization of SDDS and SDS. Knowing the values of mole fractions of surfactants in the mixed micelle, it is also possible to calculate the volume change of surfactants after the micellization process.