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 (SmC_A*) phases. Additionally, some compounds with one and two lactate groups exhibit the frustrated antiferroelectric twist grain boundary (TGB_A) 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.

Keywords:

• chiral liquid crystal
• lactate group
• chlorine substitution
• ferroelectric smectic phase
• twist grain boundary phase
• SmQ phase
• spontaneous polarisation
• dielectric properties

Acknowledgements

This work was supported by the following projects: No. IAA100100710 from the Grant Agency of the Academy of Sciences of the Czech Republic, No. 202/05/0431 from the Czech Science Foundation, AVOZ10100520 of the Academy of Sciences of the Czech Republic, No.OC175 from the Ministry of Education, Youth and Sports of the Czech Republic and bilateral Czech–Polish project No.8 (2006–07).