Effect of substrate hydrophobicity on surfactant surface-aggregate geometry

Surface aggregates of the zwitterionic surfactant dodecyldimethylammoniopropanesulfonate (DDAPS) have greater curvature on mica and silicon nitride than on graphite. This supports the hypothesis that surface aggregates will be less curved on hydrophobic solids. Lower aggregate curvature reduces the area of interaction between the hydrophobic solid and water for a given surfactant surface concentration. A zwitterionic surfactant was examined on neutral surfaces to reduce the influence of charge-charge interactions.