Neutron Spin Echo Studies on Dynamical Structures of Microemulsion

Abstract

Oil and water are naturally separated with each other due to large interfacial tension between them. By adding surfactants involving hydrophilic and hydrophobic parts, the mixtures accommodate water and oil with intervening surfactant layers. When the characteristic size of those mixtures is below 100 nm, the mixtures are transparent and called microemulsion. The system forms preferred aggregation geometries such as globular or cylindrical micelles, bicontinuous, lamellar, or hexagonal structure. Dynamical properties of the surfactant layers between oil and water play an important role in the phase behavior of these structures. Since neutron spin echo (NSE) method covers suitable space and time ranges, much attention has been paid to microemulsion system in order to observe thermal fluctuations of surfactant layers. In this review, we explain the analysis of NSE results in a microemulsion system.