title: Interaction of sodium ions with cationic surfactant interfaces.
abstract: The thermodynamically stable microemulsion and lamellar phases in the didodecyldimethylammonium bromide/water/n-decane ternary system were explored in the presence of NaBr to gain information on sodium ion-interface interactions. Experimental results, obtained by different NMR techniques, strongly suggest accumulation of sodium ions at the cationic interface. This apparently counterintuitive result is explained by invoking the dispersion potential experienced by the ions near the interface. A mechanism is proposed that can account for the dramatic shrinkage of the microemulsion phase region when an electrolyte is added.
authors.affiliation: Dipartimento di Scienze Chimiche, Università di Cagliari - CSGI Cittadella Monserrato, S.S. 554 Bivio Sestu, 09042 Monserrato, Italy.
authors.forename: Sergio
authors.initials: S
authors.lastname: Murgia
authors.forename: Filippo
authors.initials: F
authors.lastname: Portesani
authors.forename: Barry W
authors.initials: BW
authors.lastname: Ninham
authors.forename: Maura
authors.initials: M
authors.lastname: Monduzzi