Structures of lyotropic-cholesteric disk-like phases induced by prednisolon in lyotropic-nematic host phases

In the tenary system hexadecyl dimethylethylammonium bromide (C(16)Me(2)EAB r)/water/n-decanol, lyotropic-cholesteric disk-like phases (Ch(D)) were ind uced in a lyotropic-nematic matrix by addition of prednisolon. They were ch aracterised by their structural parameters obtained by X-ray measurements. In these studies, both the concentration of the prednisolon and the composi tion of the matrix were varied. The effect of the prednisolon concentration on the structural formation of the Ch(D) phase is manifested in a decrease in helix length. By orientation in a magnetic field and the use of microsl ides, separation of the spaces between the micelles was achieved as Bragg v alues perpendicular to and parallel with the optical axis. With increasing content of prednisolon in the matrix of the N-D phase, two different effect s on the anisotropy of the periodicity volume are observed. At first, the r adial extension of the micelles of the Ch(D) phase increased with constant micellar space in the normal direction. Further increase in the prednisolon concentration exceeding c(1) > 1% w/w resulted in the formation of an isot ropic periodicity volume. The effect of the composition of the N-D phase on the properties of the Ch(D) phase crucially depends on the mole ratio betw een prednisolon and the surfactant. The diminution of micellar volumes and decreasing anisotropy of the periodicity volume with increasing surfactant concentration can be understood in terms of a transition from the disk-like to the spherical micelle.