Langmuir, Vol.29, No.11, 3538-3545, 2013
Balance of Coordination and Hydrophobic Interaction in the Formation of Bilayers in Metal-Coordinated Surfactant Mixtures
Metal-ligand coordination and hydrophobic interaction are two significant driving forces in the aggregation of mixtures of Mn+ surfactants and alkyldimethylamine oxide (C(n)DMAO) in aqueous solutions. The coordinated systems exhibit rich aggregation behavior. This study investigated the effect of Mn+ ions (Zn2+, Ca2+, Ba2+, Al3+, Fe3+, La3+, Eu3+, and Tb3+) and hydrophobic chains (hydrocarbon and fluorocarbon) on the formation of metal-coordinated bilayers. We found that fluorocarbon chains and branched hydrocarbon chains are preferable to the corresponding linear hydrocarbon chains for the formation of an L-alpha phase. Moreover, L-alpha phases formed by fluorocarbon chains exhibited higher viscoelasticity than ones formed by the hydrocarbons, and the bilayers formed by branched chains were rather flexible, revealing obvious undulation. The construction of bilayers was also strongly affected by metal ions due to their variable coordination ability with C(n)DMAO. Our results contribute to the understanding of the formation of metal-coordinated bilayers, which is driven by the interplay of noncovalent forces.