Alignment of reactive LC mesogen by relief diffraction grating

Abstract

It is demonstrated experimentally that an efficient alignment of a reactive liquid crystal (LC) mesogen is achievable by employing a relief diffraction grating having a pitch smaller than the correlation length of the LC mesogen. Full alignment of the reactive LC mesogen using a 500 lines/mm diffraction grating is confirmed by polarization microscopy. A grating of 200 lines/mm exhibited partial alignment in the deepest regions of the groove. Alignment was not maintained in areas closer to the relief profile peaks of the periodic structure (which caused the spatial modulation of the alignment to occur). UV exposure of the aligned layer allowed to permanently fix the alignment due to polymerization of the unsaturated acrylate bonds. We estimate the correlation length of the reactive mesogen from this experiment to be 5 micrometers <(kappa) <2 micrometers .