Heliconical smectic phases formed by achiral molecules

TL;DR

This paper reports the discovery of various heliconical smectic phases formed by achiral molecules, revealing complex twisted structures and hierarchical organization confirmed by resonant x-ray measurements.

Contribution

It introduces new achiral molecules that form diverse heliconical smectic phases with hierarchical structures, expanding understanding of liquid crystal phase behavior.

Findings

Formation of heliconical nematic (NTB) and smectic C (SmCTB) phases.

Presence of nano-scale helices and mesoscopic helical filaments in smectic phases.

Confirmation of short pitch helical structures via resonant x-ray measurements.

Abstract

A series of asymmetric dimers with an odd number of atoms in the spacer were found to form different types of twisted structures despite being achiral. The formation of a variety of helical structures is accompanied by a gradual freezing of molecular rotation. The tight pitch heliconical nematic (NTB) phase and heliconical tilted smectic C (SmCTB) phase are formed. In the lowest temperature smectic phase, HexI, the twist is expressed through the formation of hierarchical structure: nano-scale helices and mesoscopic helical filaments. The short pitch helical structure in smectic phases is confirmed by resonant x-ray measurements.