Metachromasy Bands of Disk-Like Guests in the Host Lyotropic Liquid Crystal Disodium Chromoglycate-Water

Electronic absorption spectra of Crystal Violet (CV), Malachite Green (MG) and Methylene Blue (MB) have been investigated in the 500–700 nm region using lecithin-water and disodium chromoglycate (DSCG)-water lyotropic liquid crystals as hosts. Metachromasy bands of CV and MG, indicative of associations of guest molecules, are observed even in the mesophase of the DSCG-water system, in spite of the suppression effect of the host which tends to reduce the degree of association of guest molecules with increasing host concentration. This contrasts with the case of a rod-like guest such as MB, where no indication of association of guest molecules is observed in the DSCG lyotropic mesophase. These spectral observations on the guests in the host DSCG lyotropic liquid crystal are explained in terms of some crucial structural parameter of the guests and a lyotropic columnar structure of the host such as that proposed by Attwood et al.