Structural transitions and materials synthesis in self-assembled systems
Description
The goal of this research is to study the structural transitions in self-assembled surfactant systems and the use of such systems for materials synthesis. The anionic surfactant AOT, when contacted with an acidic phenol at a stoichiometric ratio in a non polar solvent, spontaneously forms an organogel. This system, mainly intervened by hydrogen bonding between the phenol and the surfactant, is strictly organic with low water tolerance. The organogel consists of entangled fibers when formed in the bulk. This dissertation explores the process of gel growth and presents a method to generate straight, unidirectional, densely packed gel fibers. The use of the organogel as a reverse template to synthesize porous polymerized divinylbenzene films is also discussed A second study describes the addition of a series of phenols of different hydrophobicities to a solution of CTAB micelles, which alters the shape of the surfactant assemblies from spherical micelles to elongated micelles, discs and later vesicles at progressively higher phenol concentrations. These different surfactant assemblies are exploited as templates for inorganic silica synthesis to create novel nanostructured phenolic silica composites. The shape changes of the surfactant assemblies have tremendous implications on membrane selection and design for micellar enhanced ultrafiltration A preliminary cryo-SEM study of a rigid AOT+Lecithin surfactant mesophase formed in isooctane is also presented. This surfactant mesophase allows incorporation of significant amounts of water and transforms from hexagonal columnar structure to lamellar structure as the water content is progressively increased. Through cryo-SEM, several interesting microstructural features of the surfactant mesophase are reported