S.S. Shah

Micellization parameters and electrostatic interactions in micellar solution of sodium dodecyl sulfate (SDS) at different temperatures

Abstract The effect of concentration on electrical conductance of SDS solution from 293.15–313.15 K above and below the CMC was studied. The micellization parameters, i.e. degrees of counterion binding (β) and aggregation numbers (n) were determined at different temperatures. The mass action model (MAM) was applied to calculate other micellization parameters like number of counterions per micelle (m) and micellization constant (Kc), and was also used to obtain concentration changes of counterions [Na+], surfactant ions [DS−] and micelles [Mn] with respect to total surfactant concentration. The ionic conductance changes of the counterions λ Na + , surfactant ions λ DS − and micelles (λMn) with respect to total ionic strength were evaluated by using Debye–Huckel–Onsager equations. The ionic conductivity and CMC of ionic micellar solutions and consequently all micellization parameters are influenced by temperature. The parameters like m, n and β decline, whereas ionic concentrations [Na+], [DS−] and [Mn] and ionic conductances λ Na + , λ DS − and (λMn) increase with rise in temperature.

Hydrophobic interaction of amphiphilic hemicyanine dyes with cationic and anionic surfactant micelles

The hydrophobic interaction of amphiphilic hemicyanine dyes, i.e. (dimethylamino)stilbazolium butyl sulphonate (I) and (dihexylamino)stilbazolium butyl sulphonate (II) with cetyltrimethyl ammonium bromide (CTAB), a cationic surfactant and lithium dodecyl sulphate (LDS), an anionic surfactant, was studied through absorption spectra as a function of the concentration of surfactants above and below their critical micelle concentrations. The different lengths of dialkyl chains present on these dyes exhibited hydrophobic interaction with micelles of CTAB and LDS; as a result visible spectra of both the dyes exhibited red shifts of different magnitudes when the dye molecules were solubilized into micelles. The approximate number of dye molecules per micelle was also estimated at a particular concentration of each surfactant. The solubilization depends on the dilakyl chain length of the dye together with the nature of surfactant head groups.

Differential absorbance measurements of amphiphilic hemicyanine dyes, solubilization study in anionic surfactant

Abstract The solubilization of trans -amphiphilic hemicyanine dyes by the micelles of an ionic surfactant was studied by differential spectroscopic method. The critical micelle concentration (CMC) of sodium dodecylbenzenesulfonate (SDBS) with and without hemicyanine dyes was determined by conductivity measurements. The partition coefficient between the bulk water and micelles of SDBS, K x , was calculated using both differential spectroscopic and conductance data at 25.0°C. The standard free energy change of solubilization, Δ G ° p , of these amphiphilic hemicyanine dyes was determined from the partition coefficient values. The linear dependence of the free energy change on the length of dialkyl hydrocarbon chains of the dyes on solubilization predicted the contribution of a methylene group to the free energy change, i.e. −1.091 kJ mol −1 . The increase in K x values with the hydrophobicity of the dyes indicated that the solubilization was controlled mainly by the hydrophobic interaction between the dyes and the micelles. The interaction coefficient ( θ ) and relative solubility ( S t / S o ) of dyes within the SDBS micelles has also been evaluated and discussed.

A STUDY OF MICELLIZATION PARAMETERS AND ELECTROSTATIC INTERACTIONS IN MICELLAR SOLUTION OF SODIUM DODECYL SULFATE

Abstract The electrical conductivity of sodium dodecyl sulfate (SDS) in aqueous solution was determined up to a concentration of 10 times the critical micelle concentration. The effects of solution concentration on the various interaction parameters of SDS have been studied. The mass action model was applied to micelle formation to calculate the micellization parameters: micellization constant, K c ; aggregation number, n ; and number of counterions per micelle, m . The micellization parameters also made it possible to evaluate the concentration change of monomeric surfactant ion with total surfactant concentration. The Debye–Huckel–Onsager equations have been applied to the experimental data for aqueous solution of SDS. An average degree of counterion binding to a micelle ( m / n ) and aggregation number ( n ) were determined to be 0.72 and 64, respectively. As aggregation number decreases monotonously with increase in concentration, this trend has been employed to calculate the electrical conductivity of the micelle ( λ M ).

SYNTHESIS OF CATIONIC HEMICYANINE DYES AND THEIR INTERACTIONS WITH IONIC SURFACTANTS

Abstract Cationic hemicyanine dyes, 1-methyl-4[4-(di-n-alkylamino)styryl] pyridinium betaines containing dialkyl chains in the range C1 to C4 were synthesized and characterized. The interactions of dyes with cationic surfactant, cetyltrimethylammonium bromide (CTAB) and an anionic surfactant, sodium dodecyl sulfate (SDS) were studied by measuring their visible absorption spectra as a function of surfactant concentration below and above their critical micelle concentrations. Owing to lower hydrophobicity of the dyes, the electrostatic interactions between the dyes and the surfactants seemed to play an important role in the penetration of the dyes into the surfactant micelles.

Microemulsions in Enhanced Oil Recovery: A Review

Abstract Microemulsions have recently made advances in enhanced oil recovery processes in which chemicals, especially surfactants, are used to recover the oil from natural oil reservoirs. This technique relies on the knowledge of interfacial properties among oil, water, and solid rock reservoirs in the occasional presence of natural gas under extreme conditions. Surfactant-based chemical systems have been reported in many academic studies and their technological implementation is a potential candidate in enhanced oil recovery (EOR) activities. For instance, it was determined that a mobilized buffer (polymer) with viscosity either equal to or greater than the mobilized oil enhanced the recovery efficiency considerably. However, EOR based on chemicals like alkaline–surfactant–polymer (ASP) is a complex technology requiring a high level of expertise for its industrial implementation. The surfactant–polymer interaction is a rapidly growing research area for efficient oil recovery by improving slug integrity, adsorption, and mobility control. This review article evaluates the injecting fluid system to highlight some recent advances in the use of chemicals in EOR, especially with microemulsions. It further reveals the current status and future outlook for EOR technology in oil fields and describes the opportunities for strategic utilities and load growth in petroleum industry.

Partition Coefficient of Amphiphilic Hemicyanine Dyes between the Aqueous and the Micellar Phase of Sodium Dodecyl Sulfate by Differential Absorbance Spectroscopy

Abstract Solubilization in terms of hydrophobic interactions of amphiphilic hemicyanine dyes by micelles of the anionic surfactant sodium dodecyl sulfate was studied. The critical micelle concentration was determined by a specific conductivity method. The water–micelle partition coefficient ( K x ) of these dyes was determined using a differential absorbance technique. The standard free energy change of solubilization (Δ G ° p ) and free energy change per methylene group of the dyes, Δ G °(CH 2 ) at 25°C was also calculated. K x , Δ G ° p , and Δ G °(CH 2 ) were also calculated using both conductivity and differential absorbance data. Lengthening of the dialkyl chains of the hemicyanine dyes led to greater hydrophobic interaction and consequently enhanced solubility within micelles of sodium dodecyl sulfate.

SOLUBILIZATION OF SHORT CHAIN PHENYLALKANOIC ACIDS BY A CATIONIC SURFACTANT, CETYLTRIMETHYLAMMONIUM BROMIDE

Abstract The solubilization of short chain phenylalkanoic acids by the aqueous micellar solution of cetyltrimethylammonium bromide (CTAB) has been studied as a function of surfactant concentration. The micelle-water partition coefficient, Kx, and the standard free energy change of solubilization, ΔG°p, of these additives in the CTAB micelles was determined by using both differential spectroscopic and conductance data at 25.0°C. The critical micelle concentration (CMC) of CTAB in the presence of small amount of these additives was determined by conductivity method. The relative solubility and approximate number of additive molecules per micelle was also estimated at a particular concentration of the surfactant.

Solubilization of phenol and benzyl alcohol by cationic and anionic surfactant micelles

Abstract The solubilization of phenol and benzyl alcohol by the micelles of a cationic surfactant, cetyltrimethyl ammonium bromide (CTAB), and an anionic surfactant, lithium dodecyl sulfate (LDS), was studied as a function of surfactant concentration. The critical micelle concentrations (CMCs) of the two surfactants in the presence of small amounts of these additives were determined by a conductivity method at 25°C. The micelle-water partition coefficient, K x , and the standard free energy change of transfer, ΔG p 0 , of each additive from water to micelles were also calculated. K x and ΔG p 0 of phenol and benzyl alcohols between bulk water and CTAB micelles were also determined by a differential spectroscopic method at 25°C.

Interaction of flavonoids, the naturally occurring antioxidants with different media: A UV–visible spectroscopic study

Quantitative parameters for interaction of flavonoids-the naturally occurring antioxidants, with solvents and surfactants are determined using UV-visible absorption spectroscopy. The availability of flavonoids; kaempferol, apigenin, kaempferide and rhamnetin in micelles of sodium dodecyl sulfate (SDS) is reflected in terms of partition coefficient, K(c). Thermodynamic calculations show that the process of transfer of flavonoid molecules to anionic micelles of SDS is energy efficient. A distortion in flavonoids morphology occurs in case of kaempferol and apigenin in surfactant and water, exhibited in terms of a new band in the UV region of electronic spectra of these flavonoids. The partition coefficients of structurally related flavonoids are correlated with their antioxidant activities.