Dodecyltrimethylammonium bromide in water-urea mixtures: volumes, heat capacities, and conductivities

Fluorescence of 8-Anilinonaphthalene-1-sulfonate and Properties of Sodium Dodecyl Sulfate Micelles in Water–Urea Mixtures

“…It can be seen that the absence or the presence of urea (see below), Eq. [6] urea strongly decreases the partitioning of ANS and slightly reduces to increases the emission intensity of ANS bound to the micelles. At first, these effects could be due to urea-induced…”

Tl+/Na+Competitive Binding at the Surface of Dodecylsulfate Micelles in Water–Urea Mixtures

“…Among them can be mentioned the increase in the solvent dielectric constant of the medium (34) (indirect mechanism of urea action) and the replacement of water by urea at the surfactant heads (direct mechanism of urea action), with a concomitant decrease in the magnitude of the short range forces that control the specific interactions. The combination of these effects could also explain the increase in the degree of counterions dissociation associated to the presence of urea both in cationic (7,8,17) and anionic (5) micelles. Furthermore, a decrease in the structure of water associated to the presence of urea could also contribute to the decrease in selectivity, particularly when hydrophobic FIG.…”

“…Miyaghisi et al (11) performed a study of proteins (15) and alters several properties of micellar of the alteration in properties of micelles induced by pertursolutions: (A) it increases the critical micelle concentration bation in the external environment and used urea as an addiof ionic (1,5,7,9) and nonionic (1,2,6,9) surfactants; tive assumed to be unable to penetrate the micelles. Simi-(B) it decreases the micellar size of ionic (8,14) and non-larly, urea was assumed to be a nonpenetrating agent in a ionic (6) surfactants; (C) it increases the counterion dissoci-study performed by Gonzalez et al (12) regarding the effect ation degree of ionic micelles (5,7,8); (D) it increases the of additives on the solubility of naphthalene derivatives in cloud point of nonionic (2,6) and decreases the cloud point micellar solutions. Alternatively, results from recent studies of zwitterionic (10) surfactants; (E) it increases the local have been interpreted to favor a direct mechanism of urea viscosity and decreases the local polarity at the micellar action upon properties of micelles.…”

“…As a consequence of the difference in ANS emission quantum yield in water and in a hydrophobic medium and hence (Na / ) f Å (Na / ) total 0 bC D . [7] K(Tl / /Na / ) will then be given by …”

Enthalpies of dissolution of long chain-length alkyltrimethylammonium bromide salts in water at temperatures from 278.15 to 308.15 K

“…Not surprisingly therefore, the thermodynamic and transport properties of the RMe 3 NX salts in water have been studied extensively. Measurements have included molar volumes [1][2][3][4][5][6][7], electrical conductivities [4,5,[7][8][9], heat capacities [3,4,7,10], osmotic coefficients [7,11] and dilution enthalpies [12,13]. Studies relating to the micellar behaviour of RMe 3 NX salts in water and other solvents have also been reported [14,15].…”