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
arXiv:1812.06838 · doi:10.1039/C9CP04952E
Abstract
The dielectric spectra of the twist bend nematic phase of the bent shaped achiral liquid crystal dimer are studied for the determination of the different relaxation modes. The two molecular processes were assigned one to the precessional rotation of the longitudinal components of the cyanobiphenyl groups and the second to the spinning rotation of the transverse component of the dimer. The low frequency peak shows a peculiar temperature behavior at the twist bend nematic to nematic transition. This peak can be assigned to a collective fluctuation of the tilt angle of the coarse grained director N with respect the pseudo layer normal. This corresponds well with the electro clinic effect observed as a response to an electric field in electro optic experiments. The low frequency relaxation process can be identified as a Goldstone mode, related to long-scale fluctuation of the cone phase. The birefringence data in the presence of strong bias fields in the temperature range where the twist bend nematic phase is formed is interpreted as unwinding of a helix and an indication of the formation of a field induced nematic splay bend phase.
arXiv comment14 pages, 4 figures
References in corpus (13)
- Nematic twist-bend phase with nanoscale modulation of molecular orientation
- A Twist-Bend Chiral Helix of 8nm Pitch in a Nematic Liquid Crystal of Achiral Molecular Dimers
- Twist-bend heliconical chiral nematic liquid crystal phase of an achiral rigid bent-core mesogen
- Resonant carbon K-edge soft x-ray scattering from lattice-free heliconical molecular ordering: soft dilative elasticity of the twist-bend liquid crystal phase
- Statistical mechanics of bend flexoelectricity and the twist-bend phase in bent-core liquid crystals
- Elastic and viscous properties of nematic dimer CB7CB
- Molecular organization in the twist-bend nematic phase by resonant X-ray scattering at the Se K-edge and by SAXS, WAXS and GIXRD
- Nematic twist--bend phase in an external field
- Landau theory for helical nematic phases
- Nature of nematic to twist bend nematic phase transition
- Electric field distortions in structures of the twist bend nematic (NTB) phase of a bent-core liquid crystal
- Anomalous increase in nematic-isotropic transition temperature in dimer molecules induced by magnetic field
- Light scattering study of the "pseudo-layer" compression elastic constant in a twist-bend nematic liquid crystal