Vesicular dispersions of the synthetic surfactant sodium 4-(1′-heptylnonyl) benzenesulfonate (SHBS) formed by sonication change with time. Reported here are electrical conductivity and turbidity data that support the hypothesis that this dispersion ages by a process involving the diffusion of monomer from small vesicles to large ones that is akin to Ostwald ripening. Much of the change in the vesicle population immediately after sonication is due to the relaxation of a supersaturation of surfactant caused by sonication. The vesicles do not aggregate or fuse. In addition, the solubility of pure SHBS in water at 25°C is found to be 0.22 wt%, a value three times higher than that previously reported.
Bibliographical noteFunding Information:
Companies Foundation, by the National Science Foundation (Grant CBT-8351179), and by the Standard Oil Company (Ohio) with matching funds under the National Science Foundation's Presidential Young Investigator Program.