The Determination of Molecular Spatial Orientation
In this chapter, the authors determine molecular orientation of synthetic polymers in the infrared region of the spectrum serves as an example in the development of theoretical equations and experimental procedures. Internal reflection spectroscopy provides a unique complement to transmission spectroscopy since the evanescent field has electric vectors in all spatial orientations at the reflecting interface in the rarer medium. Thus, internal reflection spectroscopy (IRS) can be employed to investigate the orientation of molecules in three dimensions in a thin surface layer next to the internal reflection element. The polarized refractometry method is sensitive to the crystalline and noncrystalline phases and is surface sensitive. The agreement of the absolute values of the fractional orthogonal orientation fractions from the IRS, X-ray diffraction, and polarized refractometry methods confirms the applicability of the IRS method.