Interaction of rigid Schiff base amphiphiles with water structure modifiers at air/water interface

Organized assemblies of Langmuir monolayers of 3-methoxy-6-nitro-N-benzilidene octadecylamine (MNBA), a novel rigid Schiff base amphiphile at air/water interface have been studied using various water structure modifiers like glycine (GLY), urea (UR) and melamine (MEL) in the subphase. Surface pressure–molecular area (π–A), reflection spectra at air/solution interface and FTIR, X-ray photoelectron (XPS) elemental analysis and atomic force microscopy (AFM) of the Langmuir–Blodgett films (LB films) have been carried out on the films of MNBA bound to GLY, UR and MEL. Depending on the number of available amino groups, direct hydrogen bonding induced two dimensional grid architecture in the amphiphile occurs in the monolayers of at air/water interface with MEL in the subphase, characterized by periodic non-dense-packing of the molecules while GLY and UR show organization which are less tightly bound. Binding of MNBA to the three compounds have been analysed using the Langmuir isotherm to give a saturation guest/amphiphile ratio (α) of 0.53 indicating that the binding site of one MEL molecule was formed co-operatively with two MNBA molecules.