Molecular organization in the twist-bend nematic phase by resonant X-ray scattering at the Se K-edge and by SAXS, WAXS and GIXRD

TL;DR

This study uses resonant X-ray scattering and SAXS/WAXS techniques on Se-labelled dimers to elucidate the molecular organization and helix structure in the twist-bend nematic phase, revealing a helix with a 9-12 nm pitch.

Contribution

It introduces a novel Se-labelled dimer approach combined with advanced X-ray scattering methods to analyze the Ntb phase's molecular and helix structure.

Findings

Identified a helix with a 9-12 nm pitch in the Ntb phase.

Achieved high helix orientation enabling detailed order parameter analysis.

Developed a modified model of the Ntb phase consistent with molecular conformations.

Abstract

Using a novel Se-labelled dimer mixed with DTC5C7 aligned by magnetic field, the twist-bend nematic phase (Ntb) in dimers was studied by hard X-ray resonant scattering and by small and wide angle X-ray scattering (SAXS, WAXS). Resonant diffraction spots indicated a helix with a 9-12 nm pitch in the Ntb phase. Unprecedentedly high helix orien-tation enabled deconvolution of global and local order parameters. This, combined with simultaneous resonant and non-resonant SAXS and WAXS data, allowed us to construct a modified model of the Ntb phase matching twisted molecular conformations and the local heliconical director field.