Ellipsoidal micelle formation of quaternary ammonium salt-based gemini surfactants: structural analysis through small-angle X-ray scattering.

Gemini surfactants exhibit better adsorption and aggregation properties than those of monomeric surfactants. However, to enhance the functional properties of gemini surfactants, the effect of spacer structures on their aggregation behavior must be elucidated. Small-angle X-ray scattering (SAXS) has been performed to study the aggregate structures of monomeric surfactants, but its application has not been expanded to the analysis of gemini surfactants.

Structural Analysis of Aggregates Formed by Linear- and Star-type Quaternary Ammonium Salt-Based Trimeric Surfactants Using Rheology and Small-Angle X-ray Scattering.

We performed a structural analysis of aggregates formed by two types of trimeric surfactants based on quaternary ammonium salts─linear-type 3Clin--Q and star-type 3Ctris--Q─featuring varying alkyl chain lengths () and spacer chain lengths () in aqueous solutions. We performed rheology, dynamic light scattering, and small-angle X-ray scattering measurements on the trimeric surfactants and investigated the effects of the alkyl chain length, spacer chain length, spacer skeleton structure, and surfactant concentration on their aggregation behavior. Linear-type 3Clin-3-Q transitioned from gel solutions to worm-like micelles at high concentrations, and 3Clin-3-Q became gel solutions over a wide range of concentrations.

Catalytic activity of gold nanoparticles protected by quaternary ammonium salt-based gemini surfactants with different spacer structures.

The protection and stabilization of metal nanoparticles with gemini surfactants can greatly improve their catalytic and reductive activities as well as stability, expanding their practical applicability. In this study, gold nanoparticles were prepared using three quaternary ammonium salt-based gemini surfactants with different spacer structures (2C(Spacer)) as protective agents, and their structures and catalytic activities were investigated. The size of the 2C(Spacer)-protected gold nanoparticles decreased as the ratio of [2C(Spacer)] to [Au] ([2C(Spacer)] : [Au]) increased from 1 : 1 to 4 : 1.

Effect of Spacer Structures on the Interfacial Adsorption and Micelle Properties of Quaternary Ammonium Salt-Based Gemini Surfactants.

In this study, we synthesized quaternary ammonium salt-based gemini surfactants, 2C(Spacer), with different spacer structures using ethylenediamine derivatives, and investigated their adsorption and aggregation properties by measuring their electrical conductivity, surface tension, fluorescence, and viscosity in conjunction with dynamic light scattering and small-angle X-ray scattering studies to investigate the effect of spacer structures on the properties of the gemini surfactants. The gemini surfactants with spacers containing nitrogen and oxygen atoms were highly soluble in water, whereas those with rigid spacers containing diethylene and triethylene chains exhibited low water solubility. The adsorption and orientation of the gemini surfactants at the air/water interface were significantly affected by the spacer length.