MIXED MICELLES OF THE DIMERIC SURFACTANT ETHANEDIYL-1,2-BIS(DODECYLDIMETHYLAMMONIUM BROMIDE) AND ITS CORRESPONDING MONOMER, THE DODECYLTRIMETHYLAMMONIUM BROMIDE - A NEUTRON-SCATTERING STUDY

Mixed micelles of the dimeric surfactant ethanediyl-1,2-bis(dodecyldim ethylammonium bromide), referred to as 12-2-12, and of its correspondi ng monomer dodecyltrimethylammonium bromide (DTAB) have been studied b y small angle neutron scattering using a contrast variation method, in order to obtain information on the localization of DTAB in the thread like micelles present in the mixed solutions at low DTAB mole fraction . The two surfactants are found to mix intimately, with. no evidence f or a preferential localization of the spherical micelle-forming DTAB a t the hemispherical endcaps of the threadlike micelles. Increasing DTA B mole fraction results in a decrease of the overall rigidity and mean length of the micelles. An appropriate normalization of the scatterin g curves-shows that this decreasing rigidity weakens the correlations between the micelles and suggests that this phenomenon is linked to a transition from a solution with some orientational order to a disorder ed solution.