title: Surface activity of the triflate ion at the air/water interface and properties of N,N,N-trimethyl-N-dodecylammonium triflate aqueous solutions.
abstract: The surface activity of salts added to water is orders of magnitude lower than that of surfactants. Sodium trifluoromethanesulfonate (NaTf) produced a change in surface tension with concentration, Δγ/Δc, of -13.2 mN·L/m·mol. This value is ca. 4-fold larger than those of simple salts and that of methanesulfonate. This unexpected surface effect suggested that positively charged micelles containing Tf could exhibit interesting properties. Dodecyltrimethylammonium triflate (DTATf) had a higher Kraft temperature (37 °C) and a lower cmc (5 × 10(-3) M) and degree of dissociation (0.11) than the chloride and bromide salts of DTA. Above the Kraft temperature, at a characteristic temperature t(1), the addition of NaTf above 0.05 M to a DTATf solution induced phase separation. By increasing the temperature of the two-phase system to above t(1), a homogeneous, transparent solution was obtained at a characteristic temperature t(2). These results, together with well-known triflate properties, led us to suggest that the Tf ion pairs with DTA and that the -CF(3) group may be dehydrated in the interfacial region, resulting in new and interesting self-aggregated structures.
authors.affiliation: Instituto de Química, Universidade de São Paulo, SP, Brazil.
authors.forename: F S
authors.initials: FS
authors.lastname: Lima
authors.forename: F A
authors.initials: FA
authors.lastname: Maximiano
authors.forename: I M
authors.initials: IM
authors.lastname: Cuccovia
authors.forename: H
authors.initials: H
authors.lastname: Chaimovich