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

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.

Main text: 5 pages, 4 figures Supporting information: 27 pages, 9 figures, 5 tables

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• Soft modes of the dielectric response in the twist-bend nematic phase and identification of the transition to nematic splay bend phase in the dimer CBC7CB
• Polar molecular ordering in the Nx phase of bimesogens and enantiotopic discrimination in the NMR spectra of rigid prochiral solutes
• Dipole-dipole correlations in the nematic phases of symmetric cyanobiphenyl dimers and their binary mixtures with 5CB
• Structure of the twist-bend nematic phase with respect to the orientational molecular order of the thioether-linked dimers
• Rapid Conformational Analysis of Semi-Flexible Liquid Crystals