title: 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.
authors: Université Lille Nord de France, F-59000 Lille, France.
authors: Marion
authors: M
authors: Collinet-Fressancourt
authors: Loïc
authors: L
authors: Leclercq
authors: Pierre
authors: P
authors: Bauduin
authors: Jean-Marie
authors: JM
authors: Aubry
authors: Véronique
authors: V
authors: Nardello-Rataj