REFLECTANCE INFRARED SPECTROSCOPIC ANALYSIS OF MONOLAYER FILMS AT THE AIR-WATER-INTERFACE

The transition moment direction and absorbance are reported for the CH2 stretching vibrations of H(CH2) (18)-OH (I) at 2918 and 2850 cm(-1) and for the CF2 stretching vibrations of F(CF2)(10)-(CH2)(2)-OH (II) at 1151 and 1207 cm(-1) in densely packed monolayers at an air/water interface. Packing was monitored by measuring force-area relations for the two systems. Absorbance and transition moment direction parameters are given as estimated by fitting observed s-polarized reflectance spectra obtained as a function of incidence angle to calculated theoretical reflectance spectra by minimum least-squares difference. The parameters determined from s-polarized reflectance spectra were used to calculate p-polarized reflectance spectra. The results compared well with experimental observations of p-polarized reflectance spectra. The results suggest that, at the packing densities used, the chain axis orientations are 12.9 degrees and 0 degrees for I and II, respectively.