Infrared determination of the orientation of molecules in stearamide monolayers

Abstract

The orientation of molecules in the monomolecular stearamide monolayers has been studied by infrared linear dichroism. By comparing the transmission absorption spectra carried out at different angles of incidence with the reflection absorption spectra obtained by depositing the monolayers on a metal substrate, the orientation of the dipole transition moments for a great number of normal vibration modes of the molecules may be determined to within a few degrees accuracy. Given certain assumptions, the orientation of the molecules themselves can then be deduced.

Determination of Molecular Orientation in Biaxially Oriented Ultrathin Films

“…These methods, utilizing polarized attenuated total reflectance (ATR), reflectance at grazing incidence (IRRAS), and transmittance spectra either alone or in combination, are usually not suited to the study of biaxially oriented films. [15][16][17][18][19][20][21][22][23][24][25][26][27] The only methods that can be applied to the study of such films are generally limited to the use of bands having their transition moment perpendicular or parallel to the main molecular axis. [28][29][30][31][32][33] The most promising method for studying the molecular orientation in biaxially oriented films has recently been introduced by Buffeteau et al 34 This method, which uses the anisotropic optical constants of a film to calculate its molecular orientation, has already been applied to the study of different ultrathin films.…”

Studying interfacial bonding at buried polymer–zinc interfaces

“…Each of these additives may influence the metal-polymer interfacial bonding properties. Adhesives are the functional groups determining the interfacial bonding characterizations [8][9][10]. Carboxylic functional groups such as polyesters are often used in industrial polymer coatings because of their desirable structural and interfacial performances [11,12].…”

Infrared spectroscopic study of the molecular orientation in LB-multilayers of an amphiphilic oxadiazole

“…As an example, Chollet derived an approximated formula for the determination of the angle j between the transition moment of a vibration and the surface normal using the ratio of the absorbances of the corresponding band in the transmission and in the reflection experiment, respectively [13]:…”

“…Since transmission spectroscopy at normal incidence is sensitive to transition moments within sample plane, whereas reflection spectroscopy at grazing incidence using layers on metal substrates is sensitive nearly exclusively to transition moments perpendicular to sample surface (the transversal component of the electric vector of the incident wave approximately vanishes ) [12], the combination of the results of these experiments is well suited to study molecular orientation. Evaluation of reflection spectra at grazing incidence must take into account, that due to electromagnetic theory the intensities of absorption bands for these spectra are enhanced by certain factors (m-factors) [13,14], thus increasing sensitivity. These enhancement factors summarize all the influences to the reflection process at grazing incidence caused by the interference of incident and reflected wave, the refractive indices involved and the enlarged sample area measured.…”