Orientation of Amphiphilic Molecules on Polar Substrates

A microscopic model based on the intermolecular interactions between adsorbates and substrates is developed to calculate the orientations of amphiphilic molecules on various polar substrates. The calculated orientations of a homologous series of alkyl-cyanobiphenyl molecules on solid polar substrates and at the air-water interface and their dependence on the alkyl chain length are in good agreement with the experimental values measured by optical second harmonic generation.