Dye Method to Identify the Types of Cubic Phases

Cubic phases formed in surfactant or copolymer solutions are optically-isotropic and highly viscous liquid crystals. They are mainly categorized to four types; normal micellar discontinuous (I1), reverse micellar discontinous (I2), normal bicontinuous (V1), reverse bicontinuous (V2) cubic phases. We used both water- and oil-soluble dye solutions to specify the type of cubic phase by a simple dyeing method. Water-soluble dye (Tartrazine) colors I1 phase, whereas it remains on the top of I2 phase. Oil-soluble dye (Sudan III) shows the opposite phenomena. Both dyes do color the V1 and V2 phases in binary water-surfactant systems. In the presence of oil, the water-soluble dye colors the V1 phase faster than the V2 phase. The oil-soluble dye shows the opposite rate of dyeing to bicontinuous cubic phases.