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 i n the system consisting of calcium dodecyl sulfate (CDS), octanol, and wate r was investigated at 25 degreesC. Highly dilute, iridescent lamellar phase s could be obtained with CDS/sodium dodecyl sulfate (SDS) weight ratios abo ve 85/15. There is no continuous transition from the swollen lamellar phase to the more highly dilute iridescent phase, instead, there is a miscibilit y gap with coexisting lower iridescent and upper swollen lamellar phases wh ich is more pronounced in systems containing sodium counterions. Also, the CDS/decanol/water system was investigated, in which we found a novel, highl y swollen lamellar and even an iridescent phase in an extremely narrow regi on in the phase diagram at 25 degreesC. In contrast to the pentanol-octanol systems, the decanol system displays an L-3 phase at elevated, but not at room temperature. (C) 2001 Elsevier Science B.V. All rights reserved.