PHASE-DIAGRAM OF A SYSTEM OF CATIONIC SURFACTANT AND ANIONIC POLYELECTROLYTE - TETRADECYLTRIMETHYLAMMONIUM BROMIDE HYALURONAN WATER

The phase behavior of the system tetradecyltrimethylammonium bromide (TTAB)-sodium hyaluronate (NaHy)-water has been investigated. Samples giving phase separation have been equilibrated, and the compositions of the separate phases have been determined. The results are summed up in a ternary phase diagram, the major feature of which is a droplet-shaped two-phase region, hanging from the water corner of the diagram. The two-phase region is entirely enclosed by a one-phase region. Furthermore, its shape shows marked dissymmetry with respect to the bisector of the water corner. Thus, a solution concentrated in the polyelectrolyte can dissolve a quite large amount of surfactant while a concentrated surfactant solution almost immediately phase-separates upon addition of polyelectrolyte. Phase diagrams have also been calculated theoretically, using the Flory-Huggins theory. If the surfactant is treated as a second polymer, phase diagrams of the same type as the experimental one may result. Adjusting the polymerization numbers and the interaction parameters of the theoretical system, a good agreement between experiment and theory is achieved. The presented model calculations indicate that the physical origin of the observed phase behavior is a fairly strong effective attraction between the polymer and the surfactant. © 1990 American Chemical Society.