Time-Dependent Structural Transitions in Ternary Mixture of TTAB/PBSS/TX-100

The vesicles formed from the binary mixture of 2-phenylbenzimidazole 5-sulfonic sodium salt (PBSS) and cationic surfactant, cetyltrimethylammonium bromide (CTAB), are different from common catanionic vesicles. After time, they spontaneously transform to thin and long nanotubes. In this study, we explored the transition of the vesicles in the presence of nonionic surfactant polyethylene glycol tert-octylphenyl ether (Triton X-100) to examine the stability of the vesicles. At different concentrations, the addition of TX-100 induced two novel time-dependent structural transitions, which are from small vesicles to branched nanotubes and from micelles to small vesicles, respectively. The mechanism was analyzed to be related to the flat structure of PBSS molecule and the electric attraction, which is different than large vesicle-nanotube transition. It suggests that some aggregates are not stable enough when flat-structured molecules are included. More attention should be paid in such studies of self-assembly.