Partial molar volumes of surface-active agents in aqueous solution

Abstract

The partial molar volumes 7 2 of some ionic and non-ionic surface-active agents have been determined above and below the critical micelle concentrations. The change AV:! in partial molar volumes on micelle formation is determined by molecular structure. Thus, additional methylene groups in the alkyl chain remote from the hydrophilic group give an increase in A G, while additional methylene groups in close proximity to a hydrophilic centre give a small decrease in AFz. These results indicate that in the process of micelle formation the hydration of the methylene groups adjacent to the hydrophilic group is retained.

The thickness, composition and structure of some lipid bilayers and natural membranes

“…It has been shown elsewhere [12,18] that the capacitance of the polar groups of the lipid and of the electrical double layers may be neglected. The justification for using bulk values of the dielectric constant of the hydrocarbon is that in the micelles of paraffinchain surfactants in water the hydrocarbon has effectively the same density as in bulk [2,11 ]; also, it has been pointed out [2] that, even if the chains in the bilayer were highly oriented (which they clearly are not [2]), the birefringence would be almost negligible. Although it is not needed for present purposes, the total thickness of the films may be obtained from Oe by appropriate allowance for the dimensions of the polar head groups.…”

“…The partial molar volume of the hydrocarbon solvent in the film was taken as the molar volume in the pure liquid. The assumption of bulk liquid properties for the hydrocarbon in the film, which, as mentioned above, was made by analogy with the interior of surfactant micelles in aqueous solution [11], is consistent with the electrical conductances of the films.…”

Study of valsartan interaction with micelles as a model system for biomembranes

“…where R is the gas constant (8.314 J K −1 mol −1 ), T the absolute temperature (298 K) and K x is calculated from K b = K xV [18] (CTAB partial molar volume isV = 0.3654 dm 3 mol −1 [22]) the standard free energy change for the transfer of VAL (C VAL = 1 mM) from bulk water to micellar phase is obtained ( G 0 x = −27.58 kJ mol −1 ).…”

Effect of the Media on the Quantum Yield of Singlet Oxygen (O2(1Δg)) Production by 9H‐Fluoren‐9‐one: Microheterogeneous Systems

“…1, a) is relatively small (ca. 12%, calculated from the partial molar volumes for SDS and CTAC micelles of 246.7 and 365.4 ml/mol, resp, [11]). The local concentration of FLU in the hydrophobic micellar cores is, therefore, more than eight-times higher than its overall concentration.…”