INFLUENCE OF UV IRRADIATION ON UNSATURATED FATTY-ACID MONOLAYERS AND MULTILAYER FILMS - X-RAY-DIFFRACTION AND ATOMIC-FORCE MICROSCOPY STUDY

The influence of UV radiation on the state of petroselaidic acid and elaidic acid Langmuir-Blodgett (LB) films and on petroselaidic acid Langmuir monolayers has been investigated using X-ray diffraction in the low angle region and atomic force microscopy. The interlayer spacing including the inclination angle of the molecules in the LB film, the topography of the film surface, and the effect of UV radiation has been studied. Also the odd-even intensity oscillation of X-ray diffraction peaks of Y-type LB films is discussed. The change in the state of a petroselaidic acid monolayer generated by UV irradiation was monitored by a change in barrier speed under a constant surface pressure. The recorded changes are suggested to be due to a partial polymerization of the double bonds of the fatty acid chains. An apparent activation energy of reaction of petroselaidic acid monolayers was obtained from the maximum change in state at three temperatures and was found to be 192 kJ/mol.