Small-Angle Neutron Scattering Investigation of Supramolecular Assemblies in Ternary Systems of Alkyldimethylamine Oxide/Cinnamic Acid/Water

Abstract Supramolecular assemblies in ternary systems of alkyldimethylamine oxide (C n DAO, n = 12, 16)/cinnamic acid/D 2 O were investigated by small-angle neutron scattering. In the C 12 DAO/cinnamic acid/D 2 O system, prolate ellipsoidal micelles with axial ratios of 1.3 and 2.4 were formed at mixing molar ratios X ([cinnamic acid]/[C n DAO]) of 0 and 0.2, respectively. For the C 16 DAO/cinnamic acid/D 2 O system, lamellar layers with a bilayer thickness of 30 A existed in a solution at X = 0, while rodlike micelles with a cross-sectional diameter of 50 A were constructed at X = 0.2. Vesicles in solutions at X = 0.5–1 had multilamellar layers. The bilayer thickness was 23–30 and 35–36 A for C 12 DAO/cinnamic acid and C 16 DAO/cinnamic acid vesicles, respectively. The thinner bilayer thickness suggests that the tilt or random orientation of alkyl chains may occur in lamellar bilayers and membrane bilayers. The comb-shaped arrangement is also possible in membrane bilayers by C n DAO/cinnamic acid complex.