Bowlic liquid crystal phase

There is another class of liquid crystals, the bowlic liquid crystal phase, whose molecules are bowl-like or pyramid-like, as is shown in Figure 1.13. Because of the breaking down of the up-down symmetry, the bowlic phase shows an even higher order and may be able to show ferroelectricity (Lam, 1986 Wang et al., 1989). 

Our interest in bowlic liquid crystals has arisen from the proposal that bowl shaped molecules may exhibit polar (noncentrosymmetric) organization in the liquid crystalline phases [4, 8, 9]. Indeed bowlic liquid crystals are natural noncentrosymmetric building blocks since a head-to-tail organization maximizes the interactions between bowlic cores. New methodologies for the creation of noncentrosymmetric structures in molecular solids and liquids are critical to the development of new materials with ferroelectric and second order nonlinear optical (NLO) properties [14, 15]. Liquid crystalline methods are particularly attractive since liquid crystalline materials are easily deposited for device construction and are readily aligned. 

Other liquid crystal phases composed of molecules having unusual molecular shapes are also known. Some compounds form a cone or bowl shape. These materials are often referred to as bowlic, and some typical examples are hexasubstituted tribenzocyclonones and aza-crowns (17), molecules of which stack on top of each other to form an ordered column which may have anomalous electrical conductivity. When a disklike molecule is divided by a rod-shaped spacer, the molecule (18) is referred to as a phasmid. It exhibits phases bearing some resemblance to columnar discotics. 

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