Co-existence of rod-like and globular micelles in the ctab—ctac—H 2O system. Evidence from the fluorescence of solubilized pyrene

Abstract

The co-existence of two types of micellar structures in concentrated aqueous solutions of mixtures of CTAB and CTAC (cetyltrimethylammonium bromide and chloride) bas been confirmed by studies of the fluorescence decay of solubilized pyrene. The fluorescence decay of pyrene in these mixtures is a double exponential. the short-lived component is ascribed to pyrene solubilized by rod-like micelles with Br − as principal counter-ion, the long-lived to pyrene on globular Cl −-rich micelles. Pyrene is preferentially solubilized by the former. The co-existence is suggested to be the consequence of a higher preference for Br − as a counter-ion in the case of rod-like structures.