FORMATION OF VESICULAR BILAYERS IN AQUEOUS-SOLUTIONS CONTAINING MIXTURES OF DIALKYLDIMETHYLAMMONIUM BROMIDES

DSC scans for vesicles in aqueous systems produced by mixtures of dihe xadecyldimethylammonium (DHAB where R = C16H33 in R2N+Me2Br-) and dioc tadecyldimethylammonium bromides (DOAB where R = C18H37 in R2N+Me2B-) show for most mixtures two melting points corresponding to gel to liqu id-crystal transitions which depend on the composition of the vesicula r system. The gel to liquid-crystal transitions occur over a wider tem perature range than for vesicular systems prepared using a single dial kyldimethylammonium surfactant. The resulting temperature-mole fractio n diagram is similar to that observed for continuous solid solutions. The overall pattern shows that in a given solution two types of domain s in the vesicular bilayer systems can co-exist having slightly differ ent compositions and hence melting temperatures. (C) 1998 Elsevier Sci ence B.V.