Molecular Orientation of Langmuir-Blodgett Films of .BETA.-Carotene.

Abstract

Well-ordered ultrathin β-carotene films were successfully fabricated using Langmuir-Blodgett (LB) method. Molecular orientation of the films was also investigated. Surface pressure-area isotherm suggested that β-carotene oriented perpendiculaly at the air-water interface by compression, and thus enabled to form two-dimensional film. X-ray diffraction indicated the tilt orientations of 55 and 40 degrees in the five and nine layers, respectively. Fourier-transform infrared reflection-absorption spectroscopy revealed ionone rings of β-carotene perpendicular to the substrate. The molecular orientation of the β-carotene LB films greatly depends upon the cohesive force between the conjugated chains. LB films of a mixture of β-carotene and arachidic acid were ill-defined. This is due to the fact that β-carotene thrusts up to the hydrophobic group of arachidic acid.