Phase behavior of iridescent phases with calcium dodecyl sulfate, octanol or decanol, and water, and the effect of the presence of sodium ions

The influence of sodium counterions on the highly swollen lamellar phases in the system consisting of calcium dodecyl sulfate (CDS), octanol, and water was investigated at 25°C. Highly dilute, iridescent lamellar phases could be obtained with CDS/sodium dodecyl sulfate (SDS) weight ratios above 85/15. There is no continuous transition from the swollen lamellar phase to the more highly dilute iridescent phase, instead, there is a miscibility gap with coexisting lower iridescent and upper swollen lamellar phases which is more pronounced in systems containing sodium counterions. Also, the CDS/decanol/water system was investigated, in which we found a novel, highly swollen lamellar and even an iridescent phase in an extremely narrow region in the phase diagram at 25°C. In contrast to the pentanol-octanol systems, the decanol system displays an L3 phase at elevated, but not at room temperature.