Unusual formation of small aggregates by mixing giant multilamellar vesicles

• Published in: Journal of colloid and interface science Vol. 312; no. 1; pp. 108 - 113
• Main Authors: Rodríguez-Abreu, Carlos, Shrestha, Lok Kumar, López Quintela, Manuel Arturo
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 01.08.2007; Elsevier
• Subjects: Chemistry; Colloidal state and disperse state; Dynamic light scattering; Exact sciences and technology; Fluorescence spectroscopy; General and physical chemistry; Membranes; Micelles; Micelles. Thin films; Phase behavior; SAXS; Surface physical chemistry; Vesicles; Fluorescence spectroscopy; Vesicles; Dynamic light scattering; Phase behavior; Micelles; SAXS; Vesicle; Light scattering; Fluorescence; Micelle; Small angle X ray scattering; Dynamics; Aggregate
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2006.07.042

The phase behavior and structure of aggregates in a hydrophobic block copolymer (L121)/double-tailed surfactant (AOT)/water system have been studied by phase study, fluorescence spectrometry, dynamic light scattering, transmission electron microscopy, small angle X-ray scattering (SAXS) and conductivity measurements. An isotropic, one-phase region is found between two biphasic regions containing large vesicles, namely, transparent samples are formed by mixing two turbid solutions. Depending on the AOT/L121 ratio, the isotropic region can be quite stable against temperature. The phase transition between the two regions can be detected by the used techniques, and structural transitions in the aggregates are inferred. The experimental evidence indicates that mixed aggregates are formed at very low concentrations, much lower than the critical micellar concentration of AOT. These micelle-like aggregates contain a mixed hydrophobic core, are small (2–4 nm), and seem to be quasi-spherical, which is an unexpected result since the packing parameters of the single amphiphiles do not favor such small quasi-spherical shapes. This behavior might have interesting implications in the release of substances from vesicles when their structure is disrupted.