Hydration and Micellization Processes of n-Octyl β-d-Glucopyranoside in Aqueous Solution. A Thermodynamic and Fluorimetric Study in the Absence and Presence of Salts

Abstract

A thermodynamic and fluorimetric study of a nonionic surfactant widely used in the biochemical field, n-octyl β-D-glucopyranoside (OBG), has been carried out in aqueous solution at 25 °C, in the absence and presence of salts containing divalent cations. For that purpose, three highly accurate experimental techniques have been used: density, speed of sound and steady-state fluorescence. A method for the simultaneous measurement of the speed of sound and the density has been set up. With this method, quantities such as the apparent molar volume Vφ and the apparent molar isoentropic compressibility Ks,φ of the OBG, in the binary system (OBG/water) as well as in the ternary system (OBG/salt/water), have been determined. The corresponding hydration numbers nh of the monomers, either isolated or in the micellar form, have also been evaluated. The speed of sound data permit also to obtain the critical micellar concentration, cmc, of OBG aggregates, which, together with the fluorescence results, provides the aggregation number N of the micelles. Furthermore, the fluorescence data afford interesting information regarding the micropolarity of the micellar environment. With all this information, an exhaustive analysis of the hydration and micellization processes of OBG and of the effect of salts containing divalent cations, in particular Ca 2+ , on these processes has been carried out, with special emphasis on the solute-solvent and solute-solute interactions.

Microstructure and structural transition in microemulsions stabilized by aldonamide-type surfactants

“…A lower value of I 1 /I 3 indicates an increased hydrophobic nature of the microemulsion droplets stabilized by the last compound mentioned. The obtained I 1 /I 3 ratios from 1.25 to 1.40 (for water I 1 /I 3 = 1.87) indicate a higher polarity sensed by pyren (see Table 2) in respect to, for instance, n-octyl-β-Dglucopyranoside (I 1 /I 3 = 1.35) [53]. This indicates the forming of a slightly more water imbued structure in the case of studied surfactants.…”

“…Accordingly, the relative fluorescence intensities of vibronic bands in a pyrene fluorescence emission spectrum are known to be sensitive to local polarity of the solubilized site of pyrene [53]. Thus, the site polarity of the studied o/w microemulsions stabilized with N -alkyl-N -methylgluconamides (C n -MGA) was obtained from the intensity ratio of the first and the third vibration bands of the fluorescence spectrum of pyrene I 1 /I 3 .…”

Synthesis, physico-chemical properties and complexing abilities of new amphiphilic ligands from d-galacturonic acid

“…35 It may be a consequence of the fact that in the micellar state, the hydration number of such compounds is strongly reduced. 36 These discrepancies indicate that the nature of the complexing amine group plays an important role in the aqueous phase behavior of the n-octyl (galactosid)uronamide derivatives. Intermolecular hydrogen bonds of the amine groups with neighboring water molecules seems to be favored in the furanose anomers.…”

Self-assembly, hydration, and structures in N-decanoyl-N-methylglucamide aqueous solutions: Effect of salt addition and temperature

“…The structure and properties of micelles formed by sugarbased surfactants is to attract interest, especially the influence of added electrolyte and temperature has been one of the main subjects in the research of surfactant solutions [7][8][9][10][11][12][13][14][15][16]. In depth understanding of micelle formation is of obvious, direct relevance for applications where formulations with high amounts of electrolyte are used, as well as for the attempts to identify new ones.…”