Counter Anion Effect on the Self-Aggregation of Dimethyl-di-N-octylammonium Cation: A Dual Behavior between Hydrotropes and Surfactants

Abstract

Self-aggregation of eight dimethyl-di-N-octylammonium salts ([DiC(8)]) has been investigated as a function of the nature of the counteranion. Tensiometry, conductimetry, and [DiC(8)]-selective electrode measurements highlighted three different behaviors and led to a rationalization of the aggregation process depending on the counteranion: "hydrophilic" anions (MoO(4)(2-), WO(4)(2-), SO(4)(2-), F(-)) give only unimers and micelles, whereas less hydrated anions form unimers, dimers, and either one micelle-like structure (NO(3)(-), Br(-)) or two micelle-like structures (CH(3)SO(3)(-), Cl(-)). Small-angle neutron and dynamic light scattering confirms the unusual behavior of [DiC(8)][Cl], which forms two types of aggregates: (i) disk or vesicles between 10 and 30 mM and (ii) ellipsoidal micelles above 30 mM. For [DiC(8)][MoO(4)(2-)], the formation of ellipsoidal micelles is supported between 10 and 300 mM. Finally, shapes and sizes of the aggregates are confirmed by molecular dynamic experiments.

Characterization and stability of catanionic vesicles formed by pseudo-tetraalkyl surfactant mixtures

“…The hypothesis of a stepwise association for 8-SHS is realistic and has been shown to occur in surfactant with short hydrophobic chains. 34 At 6% wt/wt in 8-SHS, giant vesicles are formed (see ESI, Fig. S5 †).…”

The DODAB–AOT–water system: vesicle formation and interactions with salts or synthetic polyelectrolytes

“…A more complex phase behavior was recently described. 28 Accordingly, DODAB self-aggregation occurs above z20.0 mmol kg À1 . Below the CAC, DODAB forms dimers and pre-micellar aggregates, depending on the overall surfactant content.…”

Amphiphile nanoarchitectonics: from basic physical chemistry to advanced applications

“…298 This cavitation bubble exerts a thermocapillary stress that sets the liquid into motion and amplifies the displacement and flow. 299,300 By compressing the rigid monolayer, lipid folds are created and used to partially block the flow. When the flow passes the fold for a vortex with streamlines circling around the centre.…”