STRUCTURE-FLUORESCENCE PROPERTIES OF SOME NAPHTHOYLENE-BENZIMIDAZOLE-BASED LANGMUIR-BLODGETT-FILMS

Naphthoylene benzimidazoles (NBIs) and related polymers possess promis ing spectral properties for photonic applications. In the present stud y we focus on the possibilities of a controlled variation of molecular aggregation of NBI chromophores of various chemical compositions and symmetries in Langmuir-Blodgett (LB) films. Very different pi-A isothe rms are found for the NBI-stearic acid (SA) complexes with different N BI isomers (cis-, trans- or a 1/2-NBI chromophore units). The interfac e behavior is explained by consideration of differences in molecular c onformations at the water surface under lateral pressure, This address es also a different type of chromophore aggregation within the LB film s. Spectroscopic, atomic force microscopy (AFM), and X-ray scattering methods are used thoroughly to study mono- and multilayers of NBI:SA c omplexes. We propose a flat-on arrangement for trans-NBI molecules and an edge-on orientation for cis- and 1/2NBI chromophores at the water surface and then in the LB films, A strong tendency for aggregation in the solution leads to a formation of different types of dimers and n- mers (depending on the isomer used) in the LB films. The type of aggre gation of NBI chromophores in molecular films affects their spectrosco pic properties. J-aggregation formation is revealed from the fluoresce nce spectra.