The Influence of Hydrophobic Counterion on the Phase Behavior of Ionic Surfactants

Abstract

Abstract This paper investigates the effects of counterion microenvironments on the phase properties of ionic surfactants. The results of different isomers of hydroxy naphthoic acids (x, y HNC) and the cationic surfactant hexadecyltrimethylammonium hydroxide (HTAOH) are included. Mixing 3,2 HNC, 2,1 HNC or 6,2 HNC with micellar solutions of HTAOH transforms the micellar microstructure into different morphologies depending on the counterion microenvironments. The vesicles at equal concentration ratio of 3,2 HNC/HTAOH and 2,1 HNC/HTAOH have been characterized by freeze fracture electron microscopy (FF-TEM) and small angle neutron scattering (SANS). 6,2 HNC/HTAOH system does not form a liquid crystalline phase (Lα-phase) at and above the equal concentration ratio. With these systems the effects that the hydrophobic counterion microenvironments have on the aggregate microstructure, rheological behavior, Krafft temperature and other physiochemical properties are discussed.