Ionic gemini surfactants are known to adopt various aggregation morphologies that depend on the structure of the surfactant, the surfactant concentration, and the structure and concentration of counterions. We are studying the transition from spherical to rodlike micelles of the cationic gemini surfactant trimethylene 1,3 bis (dodecyldimethylammonium) dibromide (12-3-12), which is sensitive to added counterions, and the similar surfactant tetramethylene 1,4 bis (dodecyldimethylammonium) dibromide (12-4-12), which is rather insensitive to the added counterions so it serves as a control. Previously, viscosity measurements inferred a sphere to rodlike phase transition with the addition of p-fluorobenzoate to 20 mM of 12-3-12, and now we seek to further describe and quantify this transition. To determine morphology and aggregate size, we measure the diffusion of the aggregates using ferrocene as an electrochemically active and NMR active probe. Due to its hydrophobic nature, ferrocene resides in the micelles, allowing diffusion of the aggregates to be determined with both electrochemistry and pulsed-field-gradient NMR.

Ferrocene probe investigations of the sphere to rod phase transition for cationic gemini surfactants

248th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.