AGGREGATION STUDIES IN ALKANOIC ACID-ALKYLAMINE-WATER SYSTEMS

Alkylamines show amphiphilic properties such as self-association in po lar solvents and accumulation at interfaces. However, their complexati on with alkanoic acids changes drastically their colloidal properties. Phase equilibria at different temperatures in the systems hexanoic ac id-hexylamine-water, heptanoic acid-heptylamine-water and octanoic aci d-octylamine-water were determined in order to elucidate the structure in the isotropic solution phases. Densities, surface tensions, electr ical conductivities and viscosities were measured at 298.2 K. Self-dif fusion coefficients were also determined both in the acid- and in the amine-rich part of the phase diagram in order to confirm if a componen t is confined to closed aggregates. The aim of this study was to contr ibute to a better understanding of the complexation in relation to the properties of catanionic surfactants.