Abstract
In water-soluble dye, possessing -SO3- groups and the cationic surfactant (DTAB or CTAB) system, phase separation with precipitation and redissolution of precipitation were observed to result from cooperative-way between the dye and surfactant. On adding cationic surfactant to the dye aqueous solution, insoluble sedimentation occured. With further increase in cationic surfactant, precipitation was completely redissolved in aqueous solution. Flocculation was due to the electrostatic interaction between the dye and cationic surfactant and a hydrophobic layer would be formed on the dye since the tails of surfactant were facing the water phase. Redissolution was the cause for adsorption of cationic surfactant as micelles on the dye.
Redissolved solution in dye/DTAB or CTAB/water systems showed high viscosity. The addition of short-chain alcohol (1-propanol) lead to lower viscosity and prevention of aggregation. Surface tension, electro-conductivity and static light scattering measurements clearly indicated 1-propanol to be essential to interactions between the surfactant and dye.
