The N_TB phase in an achiral asymmetrical bent-core liquid crystal terminated with symmetric alkyl chains

ABSTRACT

The characteristics of the twist-bend nematic (N_TB) phase of an achiral asymmetrical rigid bent-core liquid crystal (LC), the ends of which are terminated by symmetric alkyl chains, are reported. The nematic–nematic phase transition and its properties are studied by differential scanning calorimetry (DSC), polarising microscopy and the electro-optic techniques. Large domains of opposite handedness are observed in the absence of the external field in the N_TB phase. Another set of periodic striped pattern consisting of domains with sharp boundaries is formed when a high-frequency electric field with a magnitude above its threshold is applied across a planarly aligned cell. The neighbouring domains are of opposite chirality. The temperature dependence of the heliconical angle θ₀ is determined from the birefringence measurements using Haller’s extrapolation technique. This material shows lower values of the heliconical angle (~9.3° at a temperature of 155°C within the N_TB phase) when compared with the previously reported dimer-based twist-bend nematic LCs (31°±3°).

GRAPHICAL ABSTRACT

KEYWORDS:

• Bent-core liquid crystals
• twist-bend nematic phase
• birefringence
• textures

Acknowledgements

G Shanker thanks Dr C V Yelamaggad et al. of the Centre of Nano-science and soft matter research (CeNS), Bangalore for using their laboratory facilities.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work is supported by 13/US/I2866 from the Science Foundation Ireland as part of the US–Ireland Research and Development Partnership programme jointly administered with the United States National Science Foundation under Grant Number NSF-DMR-1410649.