The aqueous catanionic system sodium perfluorooctanoate–dodecyltrimethylammonium bromide at low concentration

Phase behavior of semifluorinated catanionic mixtures: Head group dependence and spontaneous formation of vesicles

“…In applying the RST to mixed micelles we can obtain β, the dimensionless intramicellar interaction parameter, which is related with to the molecular interactions in the mixed micelles [10,40,41]. The value of β (in k B T units) can be calculated from the equations [36]:…”

“…For the studied systems, attractive forces are associated to coulombic interactions between the head groups to hydrophobic effect. On the other hand, repulsive forces may be related to steric interactions due to the low solubility of the hydrocarbon-fluorocarbon chains [10], and to differences in chain length of both components in the mixed micelle core structure [40].…”

“…In anionic-cationic mixtures β < 0 [56], or shows a linear dependence on the fluorinated surfactant molar fraction, having an attractive behavior in the cationic rich region (negative values of β) and a repulsive behavior in the anionic rich region [10]. It is necessary to take into account the theoretical validity of using regular solution theory to describe nonideal mixing in mixed surfactant micelles.…”

“…Several reviews summarize the recent advances in catanionic surfactant mixtures and their ability to form vesicles [6,8]. However, a few investigations have been published on catanionic surfactant resulting from mixtures of hydrogenated and fluorinated surfactants [9,10]. Fluorinated surfactants, where fluorine atoms replace hydrogen atoms, show, with respect to their hydrogenated counterparts, a higher hydrophobicity, a more pronounced lowering of the water surface tension and a lower critical micelle concentration (cmc) [11][12][13][14][15].…”

Effect of alkyl chain asymmetry on catanionic mixtures of hydrogenated and fluorinated surfactants

“…In this work, we extend our earlier studies on diluted mixtures of hydrogenated and fluorinated mixtures [16][17][18] to obtain highly viscous fluids or liquid crystals at low total surfactant con- centration, focusing on the effect of the alkyl chain length, mixed ratio and the substitution of H by F atoms. The hydrogenated cationic surfactants chosen were octyltrimethylammonium and cetyltrimethyl-ammonium bromide.…”