Thermodynamically Stable Blue Phases

TL;DR

This paper demonstrates theoretically that flexoelectric effects can stabilize blue phases in chiral liquid crystals, expanding their temperature stability range by reducing elastic energy costs.

Contribution

It introduces a theoretical model showing how flexoelectricity stabilizes blue phases, explaining recent experimental discoveries and suggesting ways to further increase stability.

Findings

Flexoelectricity reduces elastic energy in blue phases.

Blue phases are stable over wider temperature ranges.

The theory aligns with experimental observations in specific materials.

Abstract

We show theoretically that flexoelectricity stabilizes blue phases in chiral liquid crystals. Induced internal polarization reduces the elastic energy cost of splay and bend deformations surrounding singular lines in the director field. The energy of regions of double twist is unchanged. This in turn reduces the free energy of the blue phase with respect to that of the chiral nematic phase, leading to stability over a wider temperature range. The theory explains the discovery of large temperature range blue phases in highly flexoelectric "bimesogenic" and "bent-core" materials, and predicts how this range may be increased further.