MICELLAR PROPERTIES OF OMEGA-HYDROXYALKYLDODECYLDIMETHYLAMMONIUM BROMIDES IN AQUEOUS-SOLUTIONS

Three omega-hydroxyalkyldodecyldimethylammonium bromide surfactants, referred to as 12-mOH, with m = 6, 8, and 12, have been synthesized and their critical micelle concentration, micelle ionization degree, and aggregation numbers have been investigated by means of electrical conductivity, spectrofluorometry, and time-resolved fluorescence quenching. Contrary to the corresponding alkyldodecyldimethylammonium bromide surfactants (referred to as 12-m) which show extensive micellar growth at relatively low surfactant concentrations (P. Lianos, J. Lang, and R. Zana, J. Colloid Interface Sci. 91, 276, 1983), the 12-60H and 12-80H surfactant micelles remain small and probably spherical up to relatively high concentrations. This striking difference in behavior reflects the fact that the alkyl chain of the 12-m surfactants is part of the micelle hydrophobic core whereas the omega-hydroxyalkyl group remains in contact with water as part of the surfactant head group. The 12-120H homologue is soluble only at temperatures above 40 degrees C and forms small micelles at 55 degrees C. When its micellar solutions are cooled below the clarification temperature slightly bluish systems are obtained, probably revealing the presence of vesicles. (C) 1995 Academic Press, Inc.