Nematic and cholesteric PDLC elaborated under shear stress

The properties of nematic and cholesteric Polymer Dispersed Liquid Crystal (PDLC) with ellipsoidal droplets are reported. The shape of the droplets ar e modified by a shear stress during the preparation. Different values of th e shear stress were used which permit an ellipticity ratio modification by a factor 10. The electro-optical properties are measured for different type s of samples and compared with theoretical previsions: transmission or refl ection under voltage, threshold voltage, response times. We also describe t he preparation of the sample, the experimental apparatus used for the shear stress, and the expected theoretical quantities like response times. When the liquid crystals are nematics, we obtain an increase of the threshold vo ltages, as predicted. The relaxation time decreases with increasing deforma tion but the diminution is not as great as predicted, When the liquid cryst als are cholesterics, the high deformations induce polygonal fields, which strongly modify the electro-optical properties of the micro-composite. The threshold voltages and response time at applied voltage decrease whereas th e relaxation time is increasing.