A POSSIBLE SIMILARITY BETWEEN LYOTROPIC CUBIC PHASES AND CHOLESTERIC BLUE PHASES

The common features in structures and properties of lyotropic cubic phases (LCP) and cholesteric blue phases (BP) are discussed. In both systems the cubic phases have nontrivial structures governed by frustrations. The frustration is connected with the double-twist in BPs and with the layer curvatures in LCPs. The structure of BP can be quantitatively described using the minimization of the Landau free energy with tensor order parameter. The order parameter of LCP is unknown till now; however, some minimization procedure can also be used for the solution of the phase problem. It is noted that in both systems the stable amorphous phases are observed (the fog phase or BPIII in BPs and L 3 phase in lyotropic crystals). The importance of the observation of «forbidden» reflections for the unequivocal identification of the space groups is emphasized. © 1990 Società Italiana di Fisica.