Molecular Structure of the Dioctadecyldimethylammonium Bromide (DODAB) Bilayer

Abstract

Dioctadecyldimethylammonium bromide (DODAB) is a double-chained quaternary ammonium surfactant that assembles in water into bilayer structures. This letter reports the molecular dynamics (MD) computer simulations of the DODAB bilayer at 25 °C. The simulations show that the surfactant membrane arranges spontaneously into the rippled phase (Pβ’) at that temperature. The ordering within the chain fragment closest to the hydrophilic head (carbon atoms 1−5) is relatively low. It grows significantly for the carbon atoms located in the center of the membrane (atoms 6−17). The C6−C17 chain fragments are well aligned and tilted by ca. 15° with respect to the bilayer normal