Solubilization sites in micellar sodium octylsulphate solutions by ultrasonic spectroscopy

Abstract

. Can. J. Chem. 60, 279 (1982). Relaxation frequencies ,f, and amplitudes A were measured ultrasonically over the 3.5-52.5 MHz range at 25°C for the fast exchange of monomer between micelles and bulk solution in micellar sodium octylsulfate solutions with solubilizates present in small amounts. The additives were cyclohexane, pyridine-2-azo-p-dimethylaniline (PADA), benzene. toluene, andp-xylene. Only cyclohexane produced no changes in f, or A . The variations in the relaxationai parameters suggested that cyclohexane was situated within the micellar core and PADA, primarily in the surface region of the micelle. Benzene and toluene were adsorbed in minute quantities into the micelle surface but, with additive concentrations beyond a few molecules per micelle, were found principally in the micellar core. Toluene, along with p-xylene, showed an initial dip in fc that may indicate that the first few molecules of these additives were incorporated into the palisade layer of the rnicelle. Chem. 60, 279 (1982). On a mesure par ultrason a des frequences allant de 3,5 a 52,5 MHz et a 25'C les frequences de relaxation fc et les amplitudes A de I'echange rapide de monomere entre les micelles et la solution dans des solutions miceliaires d'octylsulfate de sodium ayant des petites quantites de solubilisants. On a utilise comme additifs: le cyclohexane, la pyridine-azo-2 dimethylaniline (PADA), le benzene, le toluene et lep-xylene. Le cyclohexane est le seul a ne pas influencer les frequences de relaxation et les amplitudes. Les variations des parametres de relaxation suggerent que le cyclohexane est situe dans la masse micellaire alors que la PADA se trouve de f a~o n primaire dans la region de la surface de la micelle. Le benzene et le toluene sont adsorbes en petites quantites dans la surface de la micelle mais, a des concentrations croissantes de I'ordre de quelques molecules par micelle, on les a trouve principalement dans le noyau micellaire. Le toluene ainsi que le xylene revelent une diminution initiale de f, qui indique que les quelques premieres molecules de ces additifs sont incorporees dans la couche protectrice de la micelle.[Traduit par le journal]

Micelle Structure and Hydrophobic Hydration

“…44,48,57,58 Similarly, the results in the inset of Figure 4B imply that benzene-d 6 is also solubilized in a dry oil-like environment within C 9 COONa micelles, again consistent with some previous studies. 47,57 However, our results do not appear to be consistent with other studies in SDS micelles implying that that benzene is either uniformly distributed throughout the micelle 49,58 or remains at the micelle−water interface. 45 Moreover, the inset of Figure 4D shows, unexpectedly, that the CD stretch frequency of solubilized benzene-d 6 is red-shifted to a greater degree than when it is transferred from water to liquid hexane.…”

Catalysis of the reaction between sorbic acid and thiols by surfactants

“…A current view of micelles is as dynamic entities with considerable movement of the surfactant molecules, so that the nonpolar parts of surfactant molecules are continually being exposed to the aqueous environment (Woods etal., 1986); presumably they carry to the micelle surface any solutes residing within the nonpolar part of the micelle. In any case, solutes thought to be 'dissolved' within micelles exchange rapidly (Jobe et al, 1982) with the solution and, in so doing, must pass through the micelle surface, where they would encounter adsorbed species.…”

Solubilization, Surface Active and Thermodynamic Parameters of Gemini Amphiphiles Bearing Nonionic Hydrophilic Spacers

“…The experiment was done by adding different quantities of paraffin oil to 100 mL of the surfactant solution (0.15%) and dispersed into droplets by hand. The system was then mixed using a rotary shaker at 150 rpm for different time intervals (5,10,15,20,30,40, 50, 60, 70 and 80 min) at 25°C. The solubilization behaviors of the surfactant systems were measured in NTU units.…”

“…Increasing the hydrophobic chains from C 12 up to C 18 increases the host core of the giant diquaternary aggregates [10]. Increasing the aggregate volume damages these aggregates leading to smaller spherical micelles and hence decreasing their solubilizing power [29,30].…”