New chlorine‐substituted liquid crystals possessing frustrated TGB_A and SmQ phases

Abstract

Several series of chlorine‐substituted rod‐like liquid crystalline compounds have been synthesised containing a different number of lactate units in the chiral chain. Sequences of phases and phase transition temperatures were determined by differential scanning calorimetry, polarising optical microscopy and X‐ray diffraction studies. Depending on the molecule structure, the materials possess a rich variety of mesophases, i.e. the paraelectric chiral smectic A (SmA*), ferroelectric chiral smectic C (SmC*) and antiferroelectric smectic C (SmCA*) phases. Additionally, some compounds with one and two lactate groups exhibit the frustrated antiferroelectric twist grain boundary (TGBA) and smectic Q (SmQ) phases, respectively. The existence of the SmQ phase ordered in two directions was confirmed by X‐ray diffraction on a non‐oriented sample. The effects of the non‐chiral chain length and number of the chiral lactate groups on the mesomorphic properties, spontaneous polarisation, spontaneous tilt angle and complex permittivity have been studied and discussed.