Surfactant micelles mimic the microenvironment present in biological systems and can act as a medium for antioxidant studies. Moreover, the thermodynamic profile of micellization and spectroscopic studies provides very good information about interactions in these systems. Thus, the mixed micellar behavior of sodium dodecylsulfate (SDS) and cetyltrimethylammonium bromide (CTAB) at varying mole fractions of SDS was studied in (0.01, 0.02, and 0.03) mol kg−1 ʟ‐ascorbic acid(aq) solutions with the aid of various techniques viz., conductivity, density and sound velocity, and spectroscopy. From the CMC values of the mixed surfactants, the degree of ionization (β) and thermodynamic parameters (normalΔGm°, normalΔHm°, and normalΔSm°) were evaluated at 298.15, 308.15, and 318.15 K. The UV absorption spectra were recorded in (1–3) × 10−4 mol kg−1 ʟ‐ascorbic acid(aq) solutions at various mole fractions of SDS. The proton (1H) NMR spectra of mixed (SDS + CTAB) surfactants were studied in (0.01–0.03) mol kg−1 ʟ‐ascorbic acid solutions. Hydrodynamic diameters (Dh) of mixed micellar aggregates were obtained from the dynamic light scattering (DLS) studies. The present studies suggest the predominance of ionic‐hydrophilic interactions between the ionic head groups {O‐SO3− or N+ (CH3)3} of surfactants and the polar (–OH, –C=O and –O–) sites of ʟ‐ascorbic acid.
We have examined the mixed micellar behavior of {amphiphilic drug; chlorpromazine hydrochloride (CPZ) + cationic surfactant; cetyltrimethylammonium bromide (CTAB)} at varying mole fractions of CPZ (αCPZ = 0.2, 0.4, 0.6, and 0.8) in (0.1, 0.3, and 0.5) mol kg−1 glycine(aq) solutions at 298.15, 308.15, and 318.15 K, by using conductometric, volumetric, isentropic compressibility, UV–visible absorbance, fluorescence, and dynamic light scattering (DLS) techniques. The critical micelle concentration (CMC) values obtained from above measurements have been utilized to calculate the thermodynamic parameters (ΔG°m, ΔH°m, and ΔS°m) and degree of ionization (α) at studied temperatures and concentrations. The partial specific volume (φv), partial specific isentropic compression (φκ), and isentropic compressibility (κs) have been calculated from the experimental density and speed of sound measurements and the results have been used to elucidate different interactions occurring in these systems. These results are further supported by UV–visible absorbance and fluorescence spectroscopic studies. The hydrodynamic diameters (Dh) of the mixed micellar system have been measured from the DLS studies. Thermodynamic and spectroscopic studies depict the dominance of hydrophobic/hydrophilic‐hydrophobic interactions between the alkyl (R = C16H33) chain of CTAB or hydrophobic tricyclic scaffolding of CPZ/Br−/N+‐CH3 group of CTAB or hydrophilic group i.e., tertiary amine portion of CPZ with hydrophobic group of glycine.
Studies on the interactions of surfactant molecules with watersoluble vitamins have significance in pharmaceutical, biological, and industrial processes. Their mixed micelles can be used as a model for understanding the complex behavior encountered in food and biological assemblies. In this context, self-assembling properties of hexadecyltrimethylammonium bromide, HTAB, and sodium cholate, NaC, and their mixtures at molar fractions, α HTAB = (0.02, 0.04, and 0.13), have been investigated in water as well as in (1, 2, and 3) × 10 −4 mol•kg −1 pyridoxine HCl (aq) (vitamin B 6 ) solutions by employing various techniques. Critical micelle concentration, degree of ionization (g), and standard thermodynamic entities (ΔG 0 m , ΔH 0 m , and ΔS 0 m ) of micellization which state the physicochemical properties of the studied system have been determined from the conductivity measurements at 298.15, 308.15, and 318.15 K. The partial specific volume (φ v ), isentropic compressibility (κ s ), and partial specific isentropic compressibility (φ κ ) were evaluated using the density and sound velocity data. UV−visible absorption and fluorescence emission spectra were recorded for pyridoxine HCl (aq) solutions in the presence of HTAB and NaC and mixed (HTAB + NaC) surfactants at α HTAB = (0.02, 0.04, and 0.13) and at T = 298.15 K. Through dynamic light scattering studies, the hydrodynamic diameters (D h ) of aggregates have been examined.
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