Structure Study of Supermonomolecular Layers in Langmuir–Blodgett Films. Surface Active Squarylium Dye–Fatty Acid Binary Mixed System

Abstract

The structures of the Langmuir–Blodgett (LB) films of the ordinary mixed monolayer (LPF) and the supermonomolecular layer (HPF) of a surface active squarylium dye-icosanoic acid binary mixed system were examined by absorption spectroscopy. The absorption spectra of one unit layer of LPF with a molar mixing ratio ranging from 1/10 to 1/1 were almost the same, strongly suggesting that each component exists separately in the films. The LB films of two unit layers of LPF showed two peaks at 590 and 560 nm ascribed to intralayer and interlayer aggregates, respectively, besides the monomeric peak at 640 nm. The absorption spectra of one unit layer of HPF indicated a critical value of the mixing ratio 1/3.5 above which the 700-nm peak is observed. This peak is an indication of a multilayer consisting of pure 1 due to the interlayer interaction. The 560-nm peak observed for LPF is caused by a hindered interlayer interaction of the chromophores between the mixed monolayers.