SURFACE ACTIVITY AND PHASE BEHAVIOUR OF POTASSIUM HEPTYLENE DECYL SUCCINATE / WATER BINARY SYSTEM

The surface activity of potassium heptylene decyl succinate (PHDS) at water-air interface was studied. The obtained results showed a very good correlation between the surface activity of PHDS and concentration of surfactant solutions and temperature of the system. The phase behaviour and structure of aggregates in PHDS)/water binary system were investigated. The phase diagram of the PHDS/water binary system was obtained depending on the concentration of components and temperature of the system. It was established that due to the double hydrocarbon chain of the PHDS molecule, the lamellar liquid crystalline phase exists across a wide range of the phase diagram. It was shown that upon the addition of water, the cross-sectional area of the PHDS molecules in lamellar liquid crystals is changed insignificantly. This result was associated with the invariability of the distance of the lipophilic layers of formed lamellar liquid crystals by PHDS molecules. On the basis of video-enhanced microscopic studies, it was established that in two-phase region of the phase diagram, lamellar liquid crystals coexist with water in the form of vesicles.