Vesicle formation of disodium lauryl sulfosuccinate

Abstract

Disodium lauryl sulfosuccinate (diSLSS) is an anionic surfactant, wherein a dodecyl chain and sodium sulfosuccinate are ester-bonded. The surfactant has two hydrophilic groups—sulfonic and carboxylic acid. The diSLSS reduced the surface tension of water to 26 mN m−1. However, an inflection point indicating the critical micelle concentration in the surface-tension curve was not observed. According to dynamic light scattering measurements, the diSLSS formed ca. 160 nm of aggregates, and its zeta potential changed from − 80 to − 55 mV in the concentration range of 0.1–15 mmol L−1. The aggregate exhibited a vesicle shape when imaged with a transmission electron microscope. In general, single-chain hydrocarbon-based surfactants rarely form vesicles in aqueous solutions. Therefore, the vesicle membranes were analyzed via small-angle X-ray scattering. The interlayer distance with the water layer for multilamellar vesicles was estimated to be 3 nm in a 15 mmol L−1 diSLSS solution. Because the molecular length of diSLSS is approximately 2.2 nm, the molecular membrane for multilamellar vesicles is considered as an alternate layer, rather than an extended bilayer structure. Additionally, the strong electrostatic repulsion between the large hydrophilic groups indicates the existence of an alternate layer. The diSLSS has the merit that vesicles can be easily formed with the one component of surfactant from low concentration to 17 mmol L-1.