Aggregation properties of tetrachloroperylene-tetracarboxylic acid in binary Langmuir and Langmuir-Blodgett films

The Langmuir and Langmuir-Blodgett films formed of tetra-n-butyl-1,6,7,12-tetrachloroperylene-3,4,9,10-tetracarboxylate and its binary mixtures with 4-octyl-4′-cyanobiphenyl and arachidic acid have been studied. The Langmuir films were characterized by surface pressure versus mean molecular area isotherms and the films morphology observations were made by means of a Brewster angle microscope. The miscibility of the compounds was determined. Subsequently, the Langmuir films were transferred onto hydrophilic quartz substrates forming the monolayer Langmuir-Blodgett films. The electronic absorption and fluorescence spectra reveal aggregation of the chromophores in ground state driven by π-π molecular orbitals interactions. Perylene-like dye aggregation depends upon the dye concentration in the dye/liquid crystal mixed films and is concentration-independent in dye/arachidic acid one.