Highly Swollen Lamellar Phases in the System Calcium Dodecyl Sulfate, Pentanol or Hexanol, and Water

Calcium dodecyl sulfate (CDS) is insoluble both in water and in alcohols at room temperature. However, it can be dissolved up to high concentrations in mixtures of water and ethanol, propanol, or butanol. No liquid-crystalline phases are formed with ethanol and propanol at 25 °C but are observed with butanol at higher concentrations of CDS. With pentanol and hexanol, lamellar phases are observed, which can be swollen largely. Neutron scattering measurements of phases with a weight ratio CDS:hexanol = 1:1 show stiff lamellae in the concentration range of 1.5-25 wt % CDS. The repeat distance grows linearly with dilution. The effective thickness for the hydrocarbon part of the lamellae decreases to some extent at high CDS concentrations.