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Thermal hysteresis shown by polymer dispersed cholesteric liquid crystals

Anita Kanwar, Sureshchandra J.Gupta

We present a comprehensive study on the mixtures of Polymer Dispersed Cholesteric Liquid Crystal (PDCLC) samples made using polymer PN393, nematic liquid crystal mixture TL205 doped with Cholesteryl material in different proportions. The phase transition temperatures of the samples thus prepared were studied using Fabry Perot Scattering Studies (FPSS) and Optical PolarizationMicroscopy (OPM). These temperatures were verified by Differential Temperature Analysis (DTA). We found that thermal response of the sample strongly depends upon the amount of the chiral dopant added to the sample. The thermal hysteresis effect shown by the samples depends on the heating and cooling rates. Concentration of the Cholesteric material and type of polymer used plays an important role in the variation of the width of the hysteresis curve. These temperature effects are completely reversible making them useful as switching devices.