Field-induced oblique helicoidal cholesteric phases in mixtures of chiral and achiral liquid crystalline molecules

ABSTRACT

We present a mean field theory to describe phase transitions in mixtures of chiral and achiral liquid crystalline molecules in the presence of an external field. When a longitudinal external field is applied parallel to the pitch axis of a chiral nematic phase (N*), the director of the N* phase can lead to an oblique heliconical cholesteric () state with a twist–bend distortion, in which a bend elastic constant is smaller than a twist elastic constant . We predict that the exists between N* and nematic (N) phases and can be controlled by temperature and concentration. We find various phase transitions: the first-order (isotropic) and the second-order , transitions, on the temperature–concentration plane. We also predict the pitch and the phase diagrams, depending on temperature and concentration under the external field.

Graphical Abstract

KEYWORDS:

• Heliconical phase
• twist–bend
• cholesteric phase
• chiral nematic
• external field

Acknowledgements

This work was supported by JSPS KAKENHI Grant Number 26400435.

Disclosure statement

No potential conflict of interest was reported by the author.

Additional information

Funding

This work was supported by the Japan Society for the Promotion of Science [26400435].