Standard Free Energy Of Micellization Research Articles

Micellization and interfacial properties of cationic gemini surfactant (12–4–12) in the presence of additives in aqueous electrolyte solution: A tensiometric study

The critical micelle concentration (CMC) of cationic gemini surfactant butanediyl-1, 4-bis(dimethyldodecylammonium bromide) with additives (primary linear alcohols (butanol, pentanol, hexanol) and primary linear amines (butylamine, pentylamine, hexylamine)) in presence of inorganic salt potassium nitrate is measured by surface tension measurements at 303K in the present study. The CMC value of the gemini decreased with increasing concentration of additives and the extent of the effect observed was in the order: C6OH>C5OH>C4OH; C6NH2>C5NH2>C4NH2. The surfactant concentration required to reduce the surface tension of solvent by 20mNm−1, C20, ratio of C20 and CMC, maximum surface excess concentration at the air/solution interface, Γmax, and minimum area per surfactant molecule, Amin, were evaluated. The interaction parameters βσ (for mixed monolayer formation at the solution/air interface), βm (for mixed micelle formation in aqueous medium) and f1m, f2m (activity coefficients) were also reported. As evident from interaction parameters, a synergistic interaction was observed both in the micelle as well as at the interface. Rubingh and Rosen models were used to evaluate the interaction parameters for the mixed micelles and at mixed monolayer, respectively. The ∆G0m, standard free energy of micellization, and ∆G0ads, free energy of adsorption, were also calculated.

The effect of sodium dodecyl sulphate on Furosemide — A cardiovascular drug in water–methanol at different temperature

Different kinds of interactions have been critically assessed in order to understand the effect of methanol (MeOH) on sodium dodecyl sulphate (SDS) containing different concentrations of Furosemide with the help of densimetric and conductometric methods. A number of physico-chemical parameters viz. apparent molar volume, apparent molar adiabatic compressibility, standard enthalpy of micellization, standard entropy of micellization and standard free energy of micellization have been calculated from experimentally measured density, velocity of sound and critical micelle concentration (CMC). The CMC has been calculated from conductivity studies. The behaviour of these parameters suggests hydrophobic hydration of the surfactant molecules in a pre-micellar region and their cooperative self-association in a micellar region. The application of the Lumry–Rajender enthalpy–entropy compensation model to the present thermodynamic parameters has also been done to calculate compensation temperature Tc, which lies in the range 270–300K suggesting solvent induced synergistic behaviour. The plot of apparent molar volume (ϕv) vs. (SDS) at different concentrations of Furosemide in 8.0mol% aqueous solution of MeOH at 303K is shown in Fig. (A) which clearly indicates the dominance of electrostatic interaction in the pre-micellar region. The data were found to be in qualitative accordance indicating the existence of intermolecular hydrophobic as well electrostatic interactions between the surfactant, MeOH and drug.

Effect of Furosemide on denaturation of lysozyme in the presence of ionic surfactant at different temperatures

The thermodynamics of Furosemide–lysozyme interaction has been studied using conductivity in combination with viscosity, density and speed of sound measurements. Lysozyme binds preferentially with Furosemide in the presence of surfactants, sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB). A number of physico-chemical parameters viz. critical micelle concentration (CMC), standard enthalpy of micellization (ΔHm°), standard entropy of micellization (ΔSm°), standard free energy of micellization (ΔGm°), apparent molar volume (ϕv), apparent molar adiabatic compressibility (ϕk) and relative viscosity (ηr) have been calculated from experimentally measured conductivity (κ), density (d), speed of sound (v) and viscosity (η). The critical micelle concentration data were found to pass through a broad minimum at 303K, which tends to become sharp with the increase in the [lysozyme] in case of SDS. Whereas for CTAB, CMC values, in general increase with the temperature and decrease with the increase in concentration of lysozyme. Experiments at different lysozyme concentrations and in the presence of surfactants suggest the predominant involvement of electrostatic interactions in the complexation process of Furosemide with lysozyme in the presence of SDS which induce unfolding of lysozyme as the surfactant concentration approaches its critical micelle concentration value, and non-specific interaction behaviour of Furosemide with lysozyme in the presence of CTAB.

Thermodynamic solution properties of pefloxacin mesylate and its interactions with organized assemblies of anionic surfactant, sodium dodecyl sulphate

This manuscript reports the physicochemical behavior of antibiotic amphiphilic drug pefloxacin mesylate (PFM) and its interaction with anionic surfactant, sodium dodecyl sulfate (SDS). The data of surface tension and electrical conductivity are helpful to detect the CMC as well as to calculate surface parameters, i.e. surface pressure, π, surface excess concentration, Γ, area per molecule of drug and standard Gibbs free energy of adsorption, ΔGads and thermodynamic parameters like standard free energy of micellization, ΔGm, standard enthalpy of micellization, ΔHm and standard entropy of micellization, ΔSm. The interaction of this drug with anionic surfactant, sodium dodecyl sulfate (SDS) was studied by electrical conductivity and UV/visible spectroscopy. This enabled us to compute the values of partition coefficient (Kx), free energy of partition, ΔGp, binding constant, Kb, free energy of binding, ΔGb, number of drug molecules per micelle, n, and thermodynamic parameters of drug–surfactant interaction.

A COMPARATIVE STUDY OF THERMODYNAMIC PROPERTIES OF STRUCTURALLY RELATED PHENOTHIAZINE DRUGS IN AQUEOUS SOLUTION

Association characteristics of amphiphilic phenothiazine drugs Fluphenazine and Trifluperazine dihydrochloride in water have been examined and their thermodynamic parameters have been calculated using conductometry. The electrical conductivity was measured as a function of concentration at various temperatures and cmc was calculated in the temperature range of 20-50C. Thermodynamic parameters i.e. standard free energy of micellization,mG , standard enthalpy of micellization, m H and standard entropy of micellization, m S were calculated from cmc value using closed association model.

A physicochemical study of SDS in aqueous solution of Furosemide: Effect of DMSO on surfactant-Furosemide interaction

Micellization behaviour of sodium dodecyl sulphate (anionic surfactant) has been studied in the presence of Furosemide (cardiovascular drug) at two concentrations i.e. 0.001 and 0.002M in 8.0mol% aqueous solution of dimethylsulphoxide using conductance (κ), densities (d), velocities of sound (v) and viscosities (η) studies in the temperature range 20–40°C at an interval of 5°C. The critical micelle concentration (cmc) of sodium dodecyl sulphate (SDS) was determined from the plots of specific conductance (κ) of SDS. The results showed that critical micelle concentration (cmc) values of surfactant decrease with increase in [Furosemide] and increase with the rise in temperature. By using cmc data, various thermodynamic parameters like standard enthalpy of micellization (ΔHmo), standard entropy of micellization (ΔSmo) and standard free energy of micellization (ΔGmo), that have direct bearing on the consequences of such interactions at the molecular level have been calculated. The apparent molar volume (ϕv) and apparent molar adiabatic compressibility (ϕκ) have also been computed using densities and velocities of sound data. The above calculated parameters were found to be sensitive towards the interactions prevailing in Furosemide–SDS–DMSO-water systems.

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

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

Enhancing the Surface Properties of Some Amine Alginate Salts with Cationic Surfactant

Abstract In this paper different amine alginate salts were prepared by neutralization of alginic acid with amine compounds (triethanol amine, tri-isopropanol amine and hexamine). The chemical structures of the prepared compounds were confirmed using Gel Permeation Chromatography (GPC) and Fourier Transform Infrared Spectroscopy (FTIR). The surface properties of the target surfactants were studied and the surface parameters were determined; including surface tension, critical micelle concentration, maximum surface excess and minimum surface area, with and without addition of dodecytrimethyl ammonium bromide as a co-surfactant. Finally, the standard free energies of micellization and adsorption of the prepared surfactants were calculated. The obtained results indicated that, the adsorption activity of the three prepared alginate salts had increased by addition of very low concentration (0.0005 m/L) of DTAB surfactant, owing to the formation of an electrostatically stabilized Surfactant-Polyelectrolyte Complex.

Synthesis and Surface Properties of Novel N-Alkyl Quinoline-Based Cationic Gemini Surfactants

Two series of cationic dimeric (gemini) surfactants are prepared with respect to key surfactants properties, such as surface activity and solubilization. The influence of both the dimerization and the spacer group is examined in order to establish structure-property relationships. The surface tension and critical micelle concentration can be markedly reduced compared to the monomeric surfactants in the pure state. The critical micelle concentration (cmc) of each series has been determined using equilibrium surface tension measurements. Furthermore, air/water interface parameters including effectiveness (πcmc), efficiency (PC20), maximum surface excess (Γ max ), and minimum surface area (A min ) have been also derived using Gibb's adsorption equation at 25°C. Standard free energies of micellization and adsorption were calculated. Solubilization behaviors of the synthesized surfactants were measured towards paraffin oil as solubilized material using light transmission technique.

Thermodynamics of Adsorption and Micellization of Triblock Copolymers of Oxyethylene and Oxybutylene in Aqueous Medium Using Surface Tensiometry

The aqueous solutions of three triblock copolymers based on polyoxyethylene and polyoxybutylene of the type EmB10Em have been analyzed by surface tension measurements. Surface activity of these triblock copolymers was studied by measuring surface parameters, like surface excess concentration, Γ2, area per molecule of polymer and standard Gibb's free energy of adsorption, ΔoGads, at various temperatures in the range of 20 to 50°C. The Effect of block length of hydrophilic portion of triblock copolymers on surface activity was investigated in this work. Miceller behavior of these triblock copolymers was also investigated using above technique. Critical micelle concentration (CMC) was determined from the plot of surface tension versus log of concentration in the range of temperature of 20–50°C. Thermodynamic parameters, standard free energy of micellization, ΔoGmic, standard enthalpy of micellization, ΔoHmic, and standard entropy of micellization, ΔoSmic were calculated from CMC value using closed association model in this range of temperature. Self assembly behavior of triblock copolymer E20B10E20 was compared with E30B10E30 and E48B10E48 triblock copolymer. Effect of temperature on surface and miceller properties of the triblock copolymers was also studied.

Ion-dipole induced interaction between cationic gemini/TTAB and nonionic (Tween) surfactants: interfacial and microstructural phenomena

The present work is focused at studying the interactions between alkanediyl-α, ω-bis(tetradecyldimethylammonium) dibromide type cationic gemini surfactants, 14-s-14 (s = 4, 5, and 6) and conventional nonionic Tweens (Tween 20, Tween 40, Tween 60, and Tween 80) and to attain a comparison with their monomeric counterpart tetradecyltrimethylammonium bromide (TTAB). The critical micelle concentrations (cmc) of mixtures of varying compositions have been evaluated using surface tension measurements. The molecular interaction parameters (β) at the monolayer air–water interface and in bulk, standard free energy of micellization (ΔG°mic), excess free energy of mixing (ΔG°ex), Gibbs energy of adsorption (ΔG°ad), and activity coefficients for the constituents in the mixtures (fi) were evaluated by employing the Clint, Rubingh, and Rosen approaches. All the parameters indicate synergism in the systems and effective involvement of the nonionic (Tween) component in the mixtures. Micelle aggregation numbers (Nagg), obtained using steady-state fluorescence quenching technique, also indicate enrichment of mixed micelles with Tweens. The micropolarity, dielectric constant and Stern–Volmer binding constants (Ksv) of the mixed systems have also been evaluated from the fluorescence data. Three-dimensional fluorescence spectroscopy has also been performed for better understanding of the quenching experiments.

Oxypropylene chain length affects the physicochemical properties of ortho ester-based gemini surfactants

In this study, we synthesized ortho ester-based surfactants, with oxypropylene chain lengths from 1 to 3000, from a short-chain ortho ester, propylene glycol, and polyoxyethylene stearyl ether. We subsequently reacted these ortho ester surfactants with propylene glycol as a spacer to yield gemini surfactants. We characterized the surface activities of each of these gemini surfactants in terms of its critical micelle concentration (CMC), surface excess concentration (ΓCMC), surface area demand per molecule (ACMC), surface tension at the CMC (γCMC), and standard free energy of micellization per mole of monomer unit (ΔGm). Increasing the oxypropylene chain length had a significant influence on the surface activity. Overall, these ortho ester-based gemini surfactants possess excellent surface properties, providing low contact angles and emulsion stability.

Novel Polymerizable Nonionic Surfactants (Surfmers) Corporate with Alkenylsuccinic Anhydride: Synthesis, Surface, and Thermodynamic Properties

In this article, nine polymerizable surfactants (surfmers) were prepared with terminal acrylate group on the hydrophilic moiety. The prepared surfmers were classified into three groups according to hydrophobic chain lengths; the first group (group I) was single-tailed with different hydrophobic chain lengths, the second group (group II) was asymmetric double-tailed, one of them was dodecenyl and the other is octyl or tetradecyl or octadecyl from fatty alcohols, and the third group (group III) is symmetric double-tailed. The chemical structures of the prepared nonionic surfmers were confirmed by mass spectra, elemental analysis, acid value titration, and FTIR and 1H NMR spectroscopy. The surface and thermodynamic parameters of the prepared surfmers were determined at 25°C including, surface tension (γ) and effectiveness, maximum surface excess (Γmax) and minimum surface area (Amin). Also, the standard free energy of micellization and adsorption were recorded. The results show that the surface and thermodynamic parameters of the prepared surfmers were sensitive to the discrepancy of surfmer tail length and their expected shape on the interface.

Synthesis and emulsification properties of novel modified polyoxyethylenated stearylamine surfactants

We have prepared a series of novel modified polyoxyethylenated stearylamine surfactants from two polyoxyethylenated stearylamines (415ST, 430ST), maleic anhydride (MA), and sodium hydrogen sulfite. We measured the surface activities of these compounds in terms of their critical micelle concentrations (CMCs), effectiveness at minimizing surface tension (γCMC), surface excess concentrations (ΓCMC), minimum average areas per surfactant molecule (ACMC), and standard free energies of micellization (ΔGm°). We studied the CMCs of the modified polyoxyethylenated stearylamine derivatives through measurements of their surface tensions, conductivities, and fluorescence (namely, the intensity ratio of the pyrene emissions at 374 and 394nm) with respect to their concentration. In addition, we also studied the surface activity in terms of the emulsification of 10% (w/w) soybean oil in the presence of these surfactants. The smallest emulsion droplets (i.e., the most stable emulsions) were obtained using the modified surfactant 415MA.

Surface parameters, biodegradability and antimicrobial activity of some amide ether carboxylates surfactants

In the present investigation, a series of amide ether carboxylates surfactants RCO-NHCH2CH2O (CH2CH2O)6CH2COONa (AEC), with different alkyl chain lengths from (C12 to C18) and (C18=, C18==) were synthesized.The surface parameters particularly effectiveness (Πcmc), efficiency (PC20), maximum surface excess (Γmax) and minimum area per molecule (Amin) values were investigated. In addition, the standard free energies of micellization (ΔGmic0) and adsorption (ΔGads0) were calculated for the prepared surfactants in aqueous solution. The prepared surfactants were tested for their biodegradability in the water of the River Nile according to the Die-away test method. Their antimicrobial activity against strains of bacteria, yeast and fungi were also investigated.

Synthesis and surface activity properties of symmetric double chains alkylbetaine surfactants derived from s-triazine

A series of symmetric double chains alkylbetaine surfactants BCn–n (n=8, 10, 12, 14) were synthesized from cyanuric chloride, aliphatic amines, N,N-dimethylpropane-1,3-diamine and sodium chloroacetate. Their structures were confirmed by MS, TOF-MS, 1H NMR, 13C NMR and FTIR. Surface tension measurements demonstrated that BC8–8 and BC10–10 have superior surface activity compared with corresponding conventional surfactants with lower CMC and γcmc. Additionally, interface behaviors of the four surfactants including adsorption and micellization can be reflected by Amin, pC20 and the calculation of the standard free energy of micellization (ΔGmicθ) and adsorption (ΔGadsθ).

1,3-Butanediol as a co-solvent for the surfactant solutions

A biphasic solution containing water and precipitated phosphocholine (PC) is presented in order to investigate the consequences of 1,3-butanediol addition on the phase behavior of PC at different 1,3-butanediol concentrations and temperature values. With increasing the concentration of 1,3-butanediol in the mixed solvent at room temperature, the biphasic solution converts into turbid phase, two phase, and finally to a clear phase that is birefringent when viewed between two crossed polarizers. The birefringent phase moves to lower 1,3-butanediol contents at higher temperature values. The birefringent phase was observed via polarizing microscopy, and its rheological parameters were measured with cone plate method. In high 1,3-butanediol contents, solutions with 2.5% of PC behave as a gel with high yield stress value. The micellization of cetyltrimethyammonium bromide (CTAB) in a series of 1,3-butanediol/water mixed solvent at room temperature was also investigated. From the conductivity measurements, the critical micelle concentration and the degree of counterion dissociation of CTAB were obtained as a function of 1,3-butanediol. Standard free energy of micellization, as a function of 1,3-butanediol contents, was also estimated and discussed. Gibbs energies of micellization were found to have a good correlation with dielectric constant and Gordon parameters.

Surface Tension, Density and Viscosity Studies on the Associative Behaviour of Oxyethylene-Oxybutylene Diblock Copolymers in Water at Different Temperatures

The associative properties of methoxy (CH3O-) ended E58B11 and hydroxyl (-OH) ended E56B19 oxyethylene-oxybuty- lene diblock copolymers in aqueous solution at different temperature are reported in this paper. For both copolymers, E represents an oxyethylene (-[CH2CH2O]-) unit and B an oxybutylene (-[CH(C2H5)CH2O]-) unit while the subscripts denote the number average block length. Surface tension measurements were used to find out surface excess concentrations (Γm), area per molecule (αs1 ) at air/water interface and Gibbs free energy for adsorption (△G0ads ) for the pre-micellar region at four temperatures. Likewise thermodynamic parameters of micellization such as, critical micelle concentrations (CMC), enthalpy of micellization (△H0mic ), standard free energy of micellization (△G0mic) and entropy of micellization (△S0mic ), were also obtained using surface tension measurements. Solution densities were used to deter-mine the partial specific volume of micelle ( Vmic) and micellar density (ρmic). Dilute solution viscosities have been used to estimate the intrinsic viscosities [η], solute-solvent interaction parameter (KH) and hydration value of micelle (Wh) at various temperatures. The effect of temperature on the micelle properties is also discussed.

Novel ionic liquid-type Gemini surfactants: Synthesis, surface property and antimicrobial activity

Novel quaternary ammonium Gemini surfactants, which turned out to be ionic liquids due to the intermolecular hydrogen bonding formed from hydroxyl groups in the spacers, were synthesized and characterized by IR, 1H NMR, 13C NMR and mass spectra. The surface properties of the Gemini surfactants were investigated by means of surface tension measurements. Surface tension parameters including surface excess concentration, Г cmc, surface area demand per molecule, A cmc, efficiency in surface tension reduction, pC 20, the effectiveness of surface tension reduction, γ cmc, critical micelle concentration, CMC, and standard free energy of micellization, Δ G a d s 0 and Δ G m i c 0 were obtained. The results indicated that compared with those of their corresponding conventional single-chain surfactant counterparts, these novel Gemini surfactants exhibited lower CMC values and greater efficiency in lowering the surface tension of water. The foamability and foam stability of these Gemini surfactants decreased with the increase in the length of the spacer chain. Gemini surfactants with alkyl chains of moderate length (C 12 or C 14) showed the best foamability and the highest foam stability. Some of the Gemini surfactants exhibited antimicrobial activity against Gram-negative bacteria Escherichia coli.

Synthesis and physicochemical properties of nonionic Gemini surfactants with a sulfonate spacer

We have prepared a series of novel nonionic Gemini surfactants, featuring sulfonate spacers, from maleic anhydride (MA), polyethylene glycol (PEG400), sodium hydrogen sulfite, and various fatty acids (C8–C18). We measured the surface activities of these compounds in terms of the critical micelle concentration (CMC), the surface tension at the CMC ( γ cmc), the surface excess concentration ( Γ cmc), the surface area occupied per molecule ( A cmc), and the standard free energy of micellization per mole of monomer unit (Δ G° m). We used pyrene fluorescence spectroscopy to characterize the hydrophobicity of the aggregates of nonionic Gemini surfactants. We measured the CMCs from the intensity ratio of the emission of pyrene in the nonionic Gemini surfactant solutions. In addition, we studied the surface activity in terms of the emulsification of 10% (w/w) olive oil in nonionic Gemini surfactant solutions. Shorter hydrophobic chains provided more-stable emulsions.