Molecular Orientation of Monolayers on Liquid Substrates: Optical Model and FT-IR Methods

Abstract

The primary emphasis of this work is on the development of an optical model which is descriptive of the reflection-absorption properties from an anisotropic monolayer located on an isotropic liquid substrate. The calculations of electric field intensities, phase changes, and reflection-absorptions are compared for isotropic and anisotropic monolayers in order to explore optical model predictions of chain anisotropy. Relationships are established between the average chain orientation angle, the anisotropic optical constants, and the angle of incident light for s-and p-polarized radiation. The modeling calculations predict that the optimum incident light angles for the extraction of orientation information occur close to the polarizing Brewster angle. A method is proposed whereby the orientation types of isotropy and chain alignment at the isotropic-equivalent angle can be distinguished.