Fast-response halogenated 4-alkyl-4′′-cyano-p-terphenyls as dual frequency addressing nematics

Abstract

Twenty-two compounds belonging to halogenated 4-alkyl-4′′-cyano-p-terphenyls have been synthesized and mesomorphic properties using polarizing optical microscope and differential scanning calorimetry have been determined. The birefringence of the compounds using prism coupling technique was determinated. The multicomponent eutectic mixture consisted of synthesised compounds was prepared and investigated. The prepared mixture exhibits very broad nematic phase range, over 140 °C, with the melting point below 0 °C. Dielectric studies revealed that prepared mixture is very useful for dual frequency adressing system, because it posses large positive dielectric anisotropy (above 22) and becomes negative above the relatively low cross-over frequency (14 kHz). The total response time of the prepared mixture measured at room temperature at low operating voltage (24 V) is short (6.5 ms) which is suitable for fast switching optical applications.