Multi-level Chirality in Liquid Crystals Formed by Achiral Molecules

TL;DR

This study demonstrates a simple achiral molecular system that exhibits complex multi-level chirality, revealing hierarchical structural organization and coupling mechanisms similar to biological materials.

Contribution

It introduces a new achiral liquid crystal system with four distinct levels of structural chirality and explores their hierarchical coupling.

Findings

Identification of four levels of chirality in the system

Coupling between different levels of chirality observed

Structural analysis using diffraction and optical methods

Abstract

In many biological materials with a hierarchical structure there is an intriguing and unique mechanism responsible for the 'propagation' of order from the molecular to the nano- or micro-scale level. Here we present a much simpler molecular system built of achiral mesogenic dimeric molecules that shows a similar complexity with four levels of structural chirality (i) layer chirality, (ii) helicity of a basic 4-layer repeating unit, (iii) a helix with a pitch of several layers and (iv) mesoscopic helical filaments. As seen in many biological systems, there is a coupling between chirality at different levels. The structures were identified by a combination of hard and soft x-ray diffraction measurements, optical studies and theoretical modelling.