Smectic electric field effects

Optics and Electric Field Effects in Nematic and Smectic A Liquid Crystals... 

M. Hareng, S. Le Berre and L. Thirant, Electric Field Effects on Biphenyl Smectic A Liquid Crystals, Appl. Phys. Letters 25 683 (1974). 

Preceding the discussion of orientational effects in LC polymers, it is worth mentioning that for a nematic and a smectic phase A of LC polymers only the S-effect was discovered and investigated. This started with works U9,124, 137 138), that demonstrated the ability of LC polymers to orient in permanent and alternating electric fields. The structural formulas of some of the polymers and copolymers investigated are given below ... 

Independently, a highly interesting problem recently revived is that of the alignment of molecules in liquid crystals due to externally applied static and alternating electric fidds. The problem was first approached by Jezewski and Kast, and was developed by Carr, Helfrich, Wysocki et al. and many others, studying various aspects, such as dielectric loss in electric fields and anomalous alignment in the smectic phase and domains, the effect of an electric field on the temperature of mesomorphic-isomorphic phase tranritions of liquid crystals, electric... 

The structure of the smectic A phase when it is composed of optically active material (i.e., smectic A ) remains the same as that for the achiral phase. The molecules are arranged in diffuse disordered layers, and there is no long-range periodic order. However, because of the molecular chirality, the environmental symmetry is reduced to [10]. As a consequence, when an electric field is applied to a chiral smectic A= phase there will be a coupling of the electroclinic susceptibility to the field and the long axes of the molecules will tilt with respect to the layer planes. The tilt angle, for relatively low applied fields, varies linearly with the field. This linear electrooptic phenomenon is called the electroclinic effect. 

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