NMR and X-ray studies of the chromonic lyomesophases formed by some xanthone derivatives

Optical microscopy, NMR and X-ray measurements are presented for four chromonic lyomesogens derived from 9-xanthone. The measurements provide details about the mesogen-water binary phase diagrams of the four compounds as well as quantitative information about the ordering and structural parameters of the mesophases. All four systems exhibit peritectic phase diagrams with a nematic (N) phase at low mesogen concentration and a hexagonal (H) phase at high concentration. The results are consistent with previously suggested models for chromonic lyomesophases in which columnar aggregates are formed by stacked mesogenic molecules. In the N phase these columns are parallel to the director but are otherwise randomly distributed in the bulk solvent, while in the H phase they form a two dimensional hexagonal array.