Infrared External Reflection Spectra of Langmuir Films of Stearic Acid and Cadmium Stearate

Abstract In situ FT-IR external reflection spectra of spread monolayers (Langmuir films) of stearic acid and Cd stearate on the water surface were recorded at various surface areas. In the stearic acid monolayer, the trans-gauche conformational change upon monolayer compression was observed, while only the all-trans conformer was observed in the Cd stearate monolayer. Even in largely expanded monolayers of Cd stearate, present is the rigid crsytalline island instead of the rather flexible island in the acid monolayer.