Imine-based highly polar achiral unsymmetrical four-ring bent shaped liquid crystals: Design, synthesis and characterization

Abstract

Herein, we have designed and synthesized a new homologous series of polar achiral bent-shaped compounds incorporating two imines and one ester linkage in the molecular framework. It has been observed that a stable and significantly longer range of nematic phase was achieved for compound A5. The homologue A6 exhibited only nematic cybotactic and smectic A mesophase. The intermediate homologue A7 and A8 displayed nematic cybotactic as well as smectic A and an unknown smectic X phase. Compounds A10 to A14, bearing the longer alkyl chains, showed the ordered smectic A and smectic X phase. In the case of smectic A and smectic X phase limits, the number of correlated units (ξ/dSAXS) was found to be around 20, while in the case of nematics, it ranged from 1-3. However, this value has been recorded up to nine correlated units in the case of cybotactic nematic ordering. All of these materials have a significantly high dipole moment of around ∼10 Debye computed via Density Functional Theory calculations, which is essential for high dielectric materials and furthermore can stabilize the highly anticipated ferroelectric nematic phase.