Alignment of molecules in Langmuir and Langmuir-Blodgett films of binary mixtures of 3,4,9,10-tetra-(n-alkoxy-carbonyl)-perylenes with a liquid crystal

Langmuir (L) and Langmuir-Blodgett (LB) films of 3,4,9,10-tetra-(n-alkoxy-carbonyl)-perylenes (nZ4–8) and their binary mixtures with 4-octyl-40-cyano-biphenyl (8CB) and 4-pentyl-400-cyano-p-terphenyl (5CT) have been studied. The surface pressure-mean molecular area isotherms of L films have been recorded, and the alignment of the molecules at the air-water interface has been estimated. The L films were transferred onto the quartz plates at surface pressures below the collapse point. The absorption and fluorescence studies of LB films by using unpolarized and linearly polarized light have been performed. The results obtained have allowed conclusions to be drawn about the arrangement of the dye and liquid crystal molecules at the air-solid substrate interface. The influence of the alkyl chain length substituted to the perylene core of the dye molecules on the molecular organization in L and LB films has been determined. The fluorescence spectra of LB films have revealed the formation of excimers. q 2005 Elsevier B.V. All rights reserved.