X-ray studies of the phases and phase transitions of liquid crystals

TL;DR

This review highlights recent x-ray diffraction research on liquid crystal phases and transitions, emphasizing the technique's role in understanding complex structures and identifying open questions in the field.

Contribution

It summarizes recent advances in x-ray studies of liquid crystal phases, focusing on twist-grain-boundary, antiferroelectric, and gel-embedded smectic phases, and discusses unresolved issues.

Findings

X-ray diffraction elucidates complex liquid crystal phases.

Open questions include the nature of smectic-C and antiferroelectric phases.

Potential existence of Bragg glass states in smectic-A gels.

Abstract

This is a short review of recent x-ray diffraction studies of the phases and phase transitions of thermotropic liquid crystals. The areas covered are twist-grain-boundary phases, antiferroelectric phases studied with resonant x-ray diffraction, and smectic phases within gel structures. In all areas x-ray diffraction has played a key role. Nonetheless open questions remain: the nature of the smectic-C variant of the twist-grain-boundary phase, the origin of antiferroelectric phases, and whether novel Bragg glass states exist for smectic-A gel samples.