Nematic liquid crystal/clay mineral composites

Novel liquid crystalline composites composed of a nematic low molar mass liquid crystal and a few percents of organized clay minerals have been prepared. The affinity of the organized clay minerals for the liquid crystal, which was evaluated by measuring their contact angles, was highly dependent on the kind of organic ammonium cations used for the organization of the clap. In the case of an organized clay having good affinity for the liquid crystal, the organized clay was dispersed homogeneously in the liquid crystal in the size of several micron meters. The composites exhibited so-called multidomain textures composed of a few micron meters domains of the liquid crystal. The composites were sandwiched between transparent conductive ITO coated glasses with 12 mu m polymer beads as a spacer and their electro-optical properties were measured. The composite cells exhibited a bistable and reversible electro-optical effect between a light scattering state and transparent state. Both the states including intermediate states between them could be selected by changing the frequency and voltage of applied electric fields. The memory effect exhibited by the composites based on the nematic liquid crystal is rather unusual since most of conventional nematic liquid crystals do not exhibit such a memory effect due to their low viscosity. The memory mechanism exhibited by the composites was proposed. (C) 1998 Elsevier Science S.A. All rights reserved.