Aggregate Formation and Gelation Behavior ofAmidoamine Oxide Surfactants in Water

Abstract

Amidoamine oxide surfactants (AAOs), in which multiple amide groups are introduced as hydrogen bonding sites into long-chain alkylamine oxides, which are general-purpose surfactants also used in kitchen detergents, form polymer-like aggregates in water or electrolyte solutions and act as low-molecular-weight gelators. AAO thickens and gels water at concentrations as low as 3%. Its gelation temperature is strongly influenced by its chemical structure. The authors investigated how the number of amide groups and the methylene chain length of each moiety affect the aggregate structure using AAOs with systematically varied chemical structures, and found the conditions that control the aggregate structure (rod-like or ribbon-like structure). It was also found that the viscoelasticity of a gel-like aqueous solution strongly depends on the aggregate structure. That is, the viscoelasticity of aqueous gel-like solutions was successfully controlled by appropriately adjusting the chemical structure of AAOs.