Polarized light emission from aligned luminescent liquid crystal films based on 4,7-disubstituted-2,1,3-benzothiadiazoles

The physical properties of a series of light emitting liquid crystal compounds based on 4,7-disubstituted-2,1,3-benzothiadiazoles were investigated in thin solid films. The films were produced on glass plates via spin-coating and then heated to give their liquid crystal mesophases leading to an anisotropic organization of the molecules inside the films after subsequent cooling down to the room temperature. An important finding was that the induced film anisotropy exhibited photo-emission of polarized light. The absorption and fluorescence spectra of the heated films had significant differences compared to the non-heated ones and interesting differences in the organization of the molecules were observed when the films were deposited on anisotropic substrates. Optical microscopy and atomic force microscopy (AFM) measurements were performed to investigate the texture and morphology of the films.