Self-Assemblies

Abstract

Surfactant function is achieved by adsorption to interface and formation of molecular assemblies. Upon increasing surfactant concentration in water, micelles and lyotropic liquid crystals are formed. These phase transitions are generally presented in a phase diagram. The structures of lyotropic liquid crystals formed in a concentrated system are mainly determined by molecular packing of surfactant molecules. Poly(oxyethylene) alkyl ethers, which are a typical type of nonionic surfactant, show structural transitions of lyotropic liquid crystals by changing polymerization degree of the hydrophilic chain due to the change in repulsion between hydrophilic groups. Such structural transitions can be explained by the critical packing parameter. The lyotropic liquid crystals can be applied to the synthesis of mesoporous materials or drug carriers in DDS. The shape of micelles formed in a dilute system also changes depending on the repulsion between hydrophilic groups. Especially wormlike micelles that have an elongated shape like polymer chains increase viscosity of a micellar solution. Wormlike micelles can be applied to DR agents or foam boosters by this feature.