Abstract
The double-chain cationic surfactant (dioctadecyl dimethyl ammonium chloride; DODAC) is used as a fabric-softener or for hair rinsing. The morphologies of DODAC agregates adsorbed on a hydrophilic surface was investigated by electron and atomic force microscopy.
An aqueous DODAC dispersion was dropped on a hydrophilic nitrocellulose membrane and was observed by transmission electron microscopy by using of negative-staining method. Multilayer vesicles (250 nm in mean diameter) were adsorbed on the hydrophilic surface. Following ultrasonication, small unilamellar vesicles could be observed on the surface.
The texture and thickness of vesicles on the mica surface was measured by an atomic force electron microscopy. The thickness of ultrasonicated vesicles after drying was 4 nm. Interior water of vesicle is eleminated by drying, thus causing the closed-shell structure to collapse, and this may have caused the bilayer to take on an interdigitated structure.
DODAC molecules do not form monolayers on a hydrophilic surface, but are adsorbed as a vesicular state.
