Ternary phase diagrams of a thermoreversible chelating non-ionic surfactant.

The behaviour of a di-block molecule associating a diamide group and a non-ionic surfactant (C(i)E(j)) is determined in a ternary surfactant/water/oil/system. Its properties are compared to the ones of a parent non-ionic surfactant C(i)E(j) through the limits of boundaries in the phase prisms. The existence of a stable microemulsion single phase in a defined temperature and concentration range is demonstrated. The extension of the microemulsion domain is limited by the presence of a gel, containing lyotropic liquid crystals as gelling agents. Temperature dependence is observed for the curvature below the temperature of zero spontaneous curvature, but the ternary system cannot produce reverse microemulsion as observed with classical C(i)E(j). The decrease of the mean curvature with temperature is inhibited by the presence of the diamide as a grafted complexing group. Liquid-liquid extraction processes with this type of surfactant are possible, but will require the presence of at least a fourth component to enlarge the water in an oil microemulsion domain.