Application Of Regular Solution Theory Research Articles

M-s-m cationic gemini and zwitterionic surfactants - a thermodynamic analysis of their mixed micelle formation.

Micelle formation enthalpies (ΔmicH values) have been calorimetrically determined at 298 K for three sets of mixed zwitterionic/cationic gemini systems consisting of N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (ZW3-12) and a series of structurally related gemini surfactants, the N,N'-bis(dimethyldodecyl)-α,ω-alkanediammonium dibromide (12-s-12) systems. From the experimental and the estimated ideal micelle formation enthalpies, the excess enthalpies were obtained. The degrees of nonideality of the interaction in the mixed micelle (βm) from our previous work was used along with the excess enthalpy values to determine excess thermodynamic quantities of the surfactants in the mixed system according to Regular Solution Theory (RST) and Motomura's theory. The excess enthalpies for the ZW3-12/12-4-12 were positive in magnitude and rose sharply when small amounts of the zwittergent were distributed into the gemini micelles. The excess enthalpies for the ZW3-12/12-5-12 and the ZW3-12/12-6-12 systems were also >0 kJ mol−1, and as a function of zwittergent composition, were quite different to those of the ZW3-12/12-4-12 mixed micelles. These results indicate that the heat of mixed micelle formation is strongly dependent on electrostatic interactions and the structure of the surfactants involved, specifically, the length of the tether group for the 12-s-12 gemini surfactants. From the calorimetric data and the application of RST and Motomura's theory, we have obtained estimates of the excess Gibbs energy and entropy of mixing. An analysis of the three thermodynamic properties suggests that the relative contributions of enthalpic and entropic effects to nonideal behavior for mixed micelles involving gemini surfactants are strongly dependent on the gemini structure.

Self-assembly thermodynamics of pH-responsive amino-acid-based polymers with a nonionic surfactant.

The behavior of pH-responsive polymers poly(N-methacryloyl-l-valine) (P1), poly(N-methacryloyl-l-phenylalanine) (P2), and poly(N-methacryloylglycyne-l-leucine) (P3) has been studied in the presence of the nonionic surfactant Brij98. The pure polymers phase-separate in an acidic medium with critical pHtr values of 3.7, 5.5, and 3.4, respectively. The addition of the surfactant prevents phase separation and promotes reorganization of polymer molecules. The nature of the interaction between polymer and surfactant depends on the amino acid structure in the side chain of the polymer. This effect was investigated by dynamic light scattering, isothermal titration calorimetry, electrophoretic measurements, small-angle neutron scattering, and infrared spectroscopy. Thermodynamic analysis revealed an endothermic association reaction in P1/Brij98 mixture, whereas a strong exothermic effect was observed for P2/Brij98 and P3/Brij98. Application of regular solution theory for the analysis of experimental enthalpograms indicated dominant hydrophobic interactions between P1 and Brij98 and specific interactions for the P2/Brij98 system. Electrophoretic and dynamic light scattering measurements support the applicability of the theory to these cases. The specific interactions can be ascribed to hydrogen bonds formed between the carboxylic groups of the polymer and the oligo(ethylene oxide) head groups of the surfactant. Thus, differences in polymer-surfactant interactions between P1 and P2 polymers result in different structures of polymer-surfactant complexes. Specifically, small-angle neutron scattering revealed pearl-necklace complexes and "core-shell" structures for P1/Brij98 and P2/Brij98 systems, respectively. These results may help in the design of new pH-responsive site-specific micellar drug delivery systems or pH-responsive membrane-disrupting agents.

Thoughts on the ideal behavior of mixed micelles and the appropriate application of regular solution theory (RST)

Solutions of mixed surfactants are often considered as solvent mixtures. Usually, mixed micellar aggregates are considered as a homogeneous mixture of solvents dispersed in a solution. But the transposition of the usual thermodynamic models of solvent mixtures to mixed micelles is not always so obvious. We discussed this point in this paper by considering several cases of surfactant mixtures. A major problem is to define the molar fraction of each surfactant in the aggregate especially when a charged surfactant is employed in the mixture, because possible dissociation of the components of the mixture must be considered in the bulk as well in the micelle. This definition is crucial especially for the characterization of the ideal behavior which is usually described by the Clint relation, as well as for the application of regular solution theory (RST) which is the most frequently applied model for interpreting the behavior of surfactant mixtures. We show in this paper how the definition of the molar fraction can change the equations and the interpretations.

Ionic liquids for acetylene and ethylene separation: Material selection and solubility investigation

Potential applications of ionic liquids (ILs) for the green separation process of acetylene in ethylene and for the storage of acetylene were investigated. To deal with this proposal, the solubilities of the unsaturated hydrocarbons in various ionic liquids were evaluated. The solubility of ethylene shows a solubility parameter-dependent behavior as indicated by the proportional relationship between the natural log value of Henry's law constant and the inverse molar volume of ILs. This correlation suggests the most important role of voids formation within IL to accommodate the solutes and the applicability of regular solution theory to model the solubility behavior. Whereas, in addition to the free-volume contribution of ILs, the solubility of acetylene is largely controlled by a specific solute–solvent interaction as a result from the association of the acidic hydrogen character in acetylene and the relative basicity of the anion. Those two different solubility behaviors result in a high absorption selectivity of acetylene over ethylene in the basic ILs. 1H NMR experiment clearly demonstrated the presence of a substantial interaction between the acetylene and the anion of IL. Interestingly, this solute–solvent interaction is reversible as indicated by the absorption–desorption test of acetylene in [BMIM][Me 2PO 4].

Application of the Kirkwood-Buff theory of solutions to acetonitrile + amide binary mixtures by using inversion procedure and regular solution theory

The Kirkwood-Buff (K-B) integrals play an important role in characterizing the intermolecular interactions in liquid mixtures. These are represented by the K-B parameters, G AA, G BB, and G AB, which reflect correlation between like-like and like-unlike species in the mixture. The K-B integrals of binary mixtures of acetonitrile (ACN) with formamide (FA), N,N-dimethylformamide (DMF), N-methylacetamide (NMA) and N,N-dimethylacetamide (DMA) at 298·15 K and at atmospheric pressure have been computed from the experimental data of ultrasonic speed and density. We have used the similar inverse procedure (as proposed by Ben-Naim) to compute the K-B Parameters of the mixtures, in which thermodynamic information on mixtures such as partial molar volumes, isothermal compressibility, and experimental data of partial vapour pressures are used. A new route has been incorporated by using regular solution theory in the computation of excess free energy for obtaining the partial vapour pressures of binary liquid mixtures. The low values of excess entropy (S E ≈ 0) obtained for these mixtures indicate the applicability of regular solution theory to these mixtures. The results obtained regarding intermolecular interaction in all the four mixtures under study from this new procedure are in good agreement with those obtained from the trends exhibited by the excess functions of these mixtures.

Inversion of the Kirkwood–Buff Theory of Solutions: Application to Tetrahydrofuran + Aromatic Hydrocarbon Binary Liquid Mixtures

The Kirkwood–Buff (K-B) integrals play an important role in characterizing the intermolecular interactions in liquid mixtures. The interaction is represented by the K-B parameters, GAA,GBB, and GAB, which reflect correlation between like-like and like-unlike species in the mixture. The K-B integrals of binary mixtures of tetrahydrofuran with benzene, toluene, o-xylene, m-xylene, p-xylene and mesitylene at 298.15 K and atmospheric pressure have been computed from the experimental data of ultrasonic speed and density. We have used the similar inverse procedure (as proposed by Ben-Naim) to compute the K-B parameters of the mixture, in which thermodynamic information on mixtures, such as partial molar volumes, isothermal compressibility and experimental data of partial vapor pressures were used. A new route has been incorporated by using regular solution theory in the computation of excess Gibbs energy for obtaining the partial vapor pressures of binary liquid mixtures. The low values of excess entropy, SE≈0, obtained for these mixtures indicate the applicability of regular solution theory to the mixtures. The values of the K-B parameter, GAB, obtained using this procedure indicate that the correlation/affinity between THF and aromatic hydrocarbon molecules follows the order: benzene > toluene > o-xylene > m-xylene > p-xylene > mesitylene, which is in good agreement with the results obtained from the trends exhibited by the excess functions of these mixtures.

Interfacial and fluorescence studies of mixed-micelle formation by 1,2-diheptanoyl- sn -glycero-3-phosphocholine with cationic surfactants

Interfacial, γ, and fluorescence measurements have been performed to evaluate the synergism in mixed cationic and zwitterionic phospholipid systems, viz. dodecyltrimethylammonium bromide plus 1,2-diheptanoyl-sn-glycero-3-phosphocholine (DHPC), tetradecyltrimethylammonium bromide plus DHPC, and hexadecyltrimethylammonium bromide plus DHPC mixtures. From the γ data the maximum surface excess and minimum area per molecule were computed and it was found that the former decreases and the latter increases with the increase in the fraction of cationic component in the binary mixture. Application of regular solution theory demonstrated that strong synergistic interactions are present which increase with the increase in length of the hydrocarbon tail of the cationic surfactant component. These interactions were considerably less in the monolayers than in the mixed micelles. The aggregation number, N agg, of DHPC shows a significant decrease upon induction of the cationic component and vice versa. The decrease in N agg is explained on the basis of an increase in the total polarity of the mixed micelles.

Chiral phase partitioning by enantioselective complexation: Characterisation by the semi-empirical application of regular solution theory

Chiral phase partitioning by enantioselective complexation: Characterisation by the semi-empirical application of regular solution theory

Application of regular solution theory to solubility in lipids and partitioning involving lipids

Expressions based on Regular Solution Theory are evaluated as a means of predicting solubilities in lipids and lipid/water partition coefficients, and confirming observed experimental trends of these parameters. Employing chlorobenzenes and chlorinated dibenzo‐p‐dioxins as solutes, and triolein as a representative lipid, it is shown that triolein/water partition coefficients (Ktw) can be expressed as a function of the solute Hildebrand parameter and molar volume. There is relatively little difference in calculated values of Ktw when a Flory‐Huggins modification is incorporated into the theoretical approach to accommodate a molecular size disparity between solutes and triolein. Results confirm that the relationship between log Ktw and the logarithm of the octan‐1‐ol/water partition coefficient (log KowJ is slightly curvilinear due to increasing solute non‐ideality in triolein, demonstrating the utility of this theoretical approach. Regular Solution Theory is also shown to be useful for predicting solubilit...

Application of regular solution theory to calculation of liquid—liquid equilibria for water-containing systems

In this paper, based on regular solution theory, a general equation for the calculation of different kinds of liquid—liquid equilibria (LLE) containing water is developed. A mixing entropy term and a long-range electrostatic term are introduced. A relationship between the interaction parameter and the absolute temperature is proposed. It can be used to correlate the LLE data for water—organic binary systems with upper and lower critical solution temperatures. The general equation has a wide application to LLE containing water—organic and water—electrolyte binary systems, as well as water—organic—organic and water—organic—electrolyte ternary systems. A simple equation for predicting the critical composition for binary LLE is deduced.

An application of regular solution theory in the study of the solubility of naproxen in some solvents used in topical preparations

The solubility of naproxen was studied in different solvents in order to test the possible application of the theory of regular solutions in preformulation studies of a pharmaceutical form for dermatological application. The solvents tested were (I): dibutyl adipate, di(2-ethylhexyl) adipate, oleyl alcohol, propylene glycol dipelargonate, isopropyl myristate, 2-octyldodecanol, decyl oleate, oleyl oleate and isopropyl palmitate. These solvents are normally used in the production of this type of pharmaceutical form and are characterised by their low polarity. Naproxen was also tested in the mixtures (II) of these solvents with others of higher polarity (ethyl and isopropyl alcohol) in proportions such that, according to the theory, the parameter of the mixture equals that of the solute. It was found that, despite the low polarity of the initial solvents (I), naproxen only seems to form regular solutions with some of them (di(2-ethylhexyl) adipate, 2-octyldodecanol and oleyl alcohol), whereas in the others both negative and positive deviations were observed as regards the solubility values predicted by the theory. These deviations may be due to the chameleonic characteristics of the solute, inducing different solute-solute or solute-solvent interactions, depending on the polarity of the solvent. This may also explain the diverse, substantial increases in solubility of naproxen in the different mixtures (II).

Application of regular solution theory in predicting equilibrium sorption of flavor compounds by packaging polymers

Equilibrium sorption values of model flavor compounds and polymers used in packaging were determined by immersing polymer samples in liquid flavor compounds. The equilibrium sorption values were normalized for crystallinity and concentration differences. The plot of ln S vs the squared difference between the solubility parameter of polymer and solvents (δ 1 -δ 2 ) 2 resulted in poor correlation. This seems to indicate that modifications are required in applying the Hildebrand-Scatchard concept of solution for the prediction of flavor sorption by polymer packaging materials. Results indicate that the consideration of polymer chain configurations and more reliable δ values for polymers may improve the prediction

Prediction of solubility of sulfonamides in water and organic solvents based on the extended regular solution theory

A method for prediction of the solubility of sulfonamides in water and in some organic solvents based on the modified Hildebrand-Scatchard equation for regular solutions is described. Introduction into the equation of the dielectric constant or solvatochromic polarity parameter of the solvent allows the applicability of regular solution theory to be extended to polar systems which are widely employed in pharmaceutical practice. The predicted solubilities of 14 sulfonamides in water at various temperatures and of eight sulfonamides in organic solvents of different polarity were compared with those determined experimentally.

Percutaneous Absorption of Alkanoic Acids 11: Application of Regular Solution Theory

The permeability coefficient, Kp, of pure unbranched alkanoic acids (C2-C7) applied to isolated porcine skin, reached a maximum in the solubility parameter (δ2) range of 9.7–10cal1/2/cm3/2. When these and other penetrants were delivered from a solvent vehicle, the following linear relationships could be demonstrated: (a) between log Kp and the molar attraction constant of the penetrant [δ2v2 or (-Ev)1/2] for six unbranched and six branched acids delivered from 1M solution in n-heptane; (b) between Kp and the partial molal volume difference in n-heptane (v2∕∕v20) for the unbranched acids; and (c) between Kp and (v2∕∕v20) for propionic acid delivered from 1M solutions in nine solvents having δ1 values in the range 7.4–12.7cal1/2/cm3/2. Drug penetrability in a given series could be assessed from knowledge of the excess free energy of the penetrant in the delivery system used.

The Gibbs free energy of mixing of natural silicate liquids; an expanded regular solution approximation for the calculation of magmatic intensive variables

The compositions of liquids coexisting with experimentally grown crystals of olivine, plagioclase, clinopyroxene, orthopyroxene, leucite, spinel, rhombohedral oxide, melilite and potassium feldspar are used to define, through mass action expressions of liquid/solid equilibrium, compositional derivatives of the Gibbs free energy of mixing of naturally occuring silicate liquids as a function of temperature, pressure and the fugacity of oxygen. The available experimental data describe these derivatives over a range of compositions which includes basic magmas. Therefore, for silicate liquids in this composition range, the topology of the Gibbs free energy of mixing can be approximated from experimental determinations of its derivatives. The majority of the existing thermodynamic data on the liquid phase is consistent with the application of regular solution theory to model the free energy of mixing. Strictly symmetric, temperature and pressure independent, regular solution interaction parameters are calibrated from this phase equilibrium data using regression techniques which have their basis in inverse theory. These techniques generate numerically stable interaction parameters which incorporate inter-variable correlation and account for experimental uncertainty. The regular solution model fits the available data on anhydrous silicate liquids to within the accuracy of the thermodynamic database +/−550 cals). Extensions to regular solution theory allow water solubility in more silica rich liquids to be modelled somewhat less accurately (+/−750 cals).

Application of Regular Solution Theory to Extraction of Salicylaldehyde Oxime Chelates

Abstract The distribution coefficients of salicylaldehyde oxime and its metal chelates, namely of Co(II), Cu(II), and Zn(II) were determined between aqueous acetate phase (μ=0.1) and eight ‘inert’ organic solvents at 25 °C. On the basis of regular solution theory, the correlation between the distribution coefficients of the ligand (PHA) and that of the metal chelates (PM) expressed by logPM=nlogPHA+ const, was shown to be valid satisfactorily in most of the systems. Hexane and cyclohexane showed abnormal behaviour in extraction with Cu(II), while with Zn(II) extraction to the desired level was not possible with these two solvents. A good correlation was also observed between the distribution coefficient of salicylaldehyde oxime and the ‘solubility parameter’ of the solvents and the solutions are shown to be regular.

Application of regular solution theory to organic solute rejection by reverse osmosis

Regular solution theory was applied to the prediction of reverse osmosis rejection of organic solute from aqueous solution, assuming that the rejection is primarily determined by the distribution of solute between the membrane and the aqueous solution. It indicates that this treatment can serve as a basis for predicting solute rejection in reverse osmosis if the membrane parameters are estimated reasonably.

Application of regular solution theory to biomembranes.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTApplication of regular solution theory to biomembranesLorna J. Bennett and Keith W. MillerCite this: J. Med. Chem. 1974, 17, 10, 1124–1125Publication Date (Print):October 1, 1974Publication History Published online1 May 2002Published inissue 1 October 1974https://doi.org/10.1021/jm00256a024RIGHTS & PERMISSIONSArticle Views55Altmetric-Citations7LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (298 KB) Get e-Alerts Get e-Alerts