Alignment of Chromonic Liquid Crystals: A Difficult Task

We present our recent effort on chromonic liquid crystal alignment. In particular, we report the alignment behavior of chromonic molecules using different hydrophobic substrates. Different materials have been used to this purpose but in all cases ribbons textures develop, indicating a slow water evaporation and/or a strong aggregation among molecules, that, as reported in a recent paper, give rise to threads connected through salt bridge bonds. Thin films of materials usually employed for thermotropic liquid crystals alignment induce schlieren textures that after 10 days evolve into ribbon textures; thin films of materials with a low surface energy orient molecules in homeotropic configuration, but the alignment is lost after two weeks as in the case of degenerate planar alignment.