Theoretical Studies Of Chiral Smectic Phases In Antiferroelectric Liquid Crystals

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Date
2015-02
Authors
TENG YONG, TAN
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Abstract
Antiferroelectric liquid crystals (AFLCs) are materials which are made up of chiral elongated molecules. The molecules tilt around the azimuthal direction from layer to layer and exhibit a number of smectic (Sm) tilted structures. These chiral smectic structures have a variety of crystallographic unit periodicities which vary from a few ( * SmC ), two ( * SmCA ), three ( * 1 SmCFI ), four ( * 2 SmCFI ), and six ( * 6 SmC d ) smectic layers. In the first part of the project, the prerequisites for the formation of the sixlayer structures are investigated theoretically using the discrete phenomenological model. Such possible structures can be obtained when the sign of the coefficients for the interactions of the nearest neighbor, third nearest neighbor, and quadrupolar coupling are considered explicitly. For the second part of the project, the dependence of the polarization direction on the structures of the * SmC ,  * 2 SmC , FI and * 1 SmCFI phases are analyzed within the framework of the clock model. The influence of the flexoelectric coefficient  and the deviation angle  on these chiral smectic structures are shown as well. In the third and last part of this project, the discrete phenomenological model is applied to study theoretically the dielectric response of chiral smectic phases, particularly in * SmC and * SmCA phases, under the influence of external harmonic electric field. The numerical results of frequency dependence of dielectric loss as well as the variation of dielectric loss in quadrupolar coupling strength for the * SmC and * A SmC phases are obtained and presented.
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Theoretical Studies Of Chiral Smectic Phases , In Antiferroelectric Liquid Crystals
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