Surface Activity of the Triflate Ion at the Air/Water Interface and Properties of N,N,N-Trimethyl-N-Dodecylammonium Triflate Aqueous Solutions

Autor(es)

Lima, F. S. ^[1] ; Maximiano, F. A. ^[1] ; Cuccovia, I. M. ^[1] ; Chaimovich, H. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Quim, BR-05508 Sao Paulo - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Langmuir; v. 27, n. 8, p. 4319-4323, APR 19 2011.
• Citações Web of Science: 15

Resumo

The surface activity of salts added to water is Air orders of magnitude lower than that of surfactants. Sodium trifluoromethanesulfonate (NaTf) produced a change in surface tension. with concentration, Delta gamma/Delta c, 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 degrees C) and a lower cmc (5 x 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. (AU)

• Processo FAPESP: 07/50970-5 - Reatividade química e biológica em interfaces
• Beneficiário: Hernan Chaimovich Guralnik
• Modalidade de apoio: Auxílio à Pesquisa - Temático