The nature of the coacervate formed in the aqueous dodecyltrimethylammonium bromide–sodium 10-undecenoate mixtures

The formation of a coacervate in mixtures of dodecyltrimethylammonium bromide (DTAB)–sodium 10-undecenoate (SUD) aqueous mixtures was studied by light scattering, ζ potential measurements, and electronic microscopy. The coacervate appears when the ζ potential goes to zero, and the energy barrier against agglomeration disappears, promoting the agglomeration of micelles. Rod-like micelles agglomerate in bundles in the DTAB-rich side of the phase diagram, while spherical or globular micelles agglomerate in clusters in the SUD-rich side. This difference explains the differences in the transition micelles–coacervate in the opposite sides of the two-phase region.