Vesicle formations at critical vesicle concentration in a polyoxyethylene type nonionic surfactant system

In a nonionic polyoxyethylene type surfactant CiEj aqueous solution below the Krafft temperature, multilamellar vesicles which have a hollow including excess water are formed (Kawabata et al., 2009). In this study, we surveyed the critical vesicle concentration, CVC, and the formation of the vesicles by means of fluorescence microscopy and light scattering. We have found that disk-like layers are formed below the CVC, and they are transformed to vesicles via a coexisting region of vesicles and disks with increasing surfactant concentration. Furthermore, by varying temperature, the transformations are induced reversibly. These phenomena could be interpreted by taking into account the elastic energy of unilamellar vesicle formation.