Liquid crystal/clay mineral composites

Novel liquid crystalline composites composed of a nematic two-frequency addressing liquid crystal (TFALC) and a few percents of various types of organized clay minerals (LCC) 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 clay. 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. Also, the LCCs were stable enough against sedimentation or aggregation under an electric field. The LCCs were sandwiched between transparent conductive In/SnO2 (ITO)-coated glasses with 12 mu m polymer beads as a spacer and their electro-optical properties were measured. The LCC cells exhibited a bistable and reversible electro-optical effect between a light scattering state and transparent state. The contrast between the light scattering and transparent memory states is highly dependent on the kind of the organized clays. The LCCs based on the organized clays with better affinity for the liquid crystal exhibited relatively higher contrast. The memory effect exhibited by the LCCs is rather unusual since most of conventional nematic liquid crystals do not exhibit such a memory effect due to their low viscosity. Their memory mechanism was proposed. (C) 1999 Elsevier Science B.V. All rights reserved.