Entropy stabilized form chirality in curved rod nematics: structure and symmetries

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Main Authors: Vanakaras, Alexandros G., Samulski, Edward T., Photinos, Demetri J.
Format: Preprint
Published: 2024
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author Vanakaras, Alexandros G.
Samulski, Edward T.
Photinos, Demetri J.
author_facet Vanakaras, Alexandros G.
Samulski, Edward T.
Photinos, Demetri J.
contents Monte Carlo molecular simulations of curve-shaped rods show the propensity of such shapes to polymorphism revealing both smectic and polar nematic phases. The nematic exhibits a nanoscale modulated local structure characterized by a unique, polar, $\rm{C}_2$-symmetry axis that tightly spirals generating a mirror-symmetry-breaking orgnization of the achiral rods=form chirality. A comprehensive characterization of the polarity and its symmetries in the nematic phase confirms that the nanoscale modulation is distinct from the elastic deformations of a uniaxial nematic director in the twist-bend nematic phase. Instead it is shown that, analogous to the isotropic-to-nematic transition, entropy stabilizes the roto-translating polar director in the polar-twisted nematic phase. The conflation of macroscale form chirality in ferroelectric nematics with that in the twist-bend nematic stems from the misattribution of the nanoscale modulation in the lower temperature nematic ''$\rm{N_X}$ phase'' found in CB7CB dimers.
format Preprint
id arxiv_https___arxiv_org_abs_2408_13325
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Entropy stabilized form chirality in curved rod nematics: structure and symmetries
Vanakaras, Alexandros G.
Samulski, Edward T.
Photinos, Demetri J.
Soft Condensed Matter
Materials Science
Chemical Physics
Monte Carlo molecular simulations of curve-shaped rods show the propensity of such shapes to polymorphism revealing both smectic and polar nematic phases. The nematic exhibits a nanoscale modulated local structure characterized by a unique, polar, $\rm{C}_2$-symmetry axis that tightly spirals generating a mirror-symmetry-breaking orgnization of the achiral rods=form chirality. A comprehensive characterization of the polarity and its symmetries in the nematic phase confirms that the nanoscale modulation is distinct from the elastic deformations of a uniaxial nematic director in the twist-bend nematic phase. Instead it is shown that, analogous to the isotropic-to-nematic transition, entropy stabilizes the roto-translating polar director in the polar-twisted nematic phase. The conflation of macroscale form chirality in ferroelectric nematics with that in the twist-bend nematic stems from the misattribution of the nanoscale modulation in the lower temperature nematic ''$\rm{N_X}$ phase'' found in CB7CB dimers.
title Entropy stabilized form chirality in curved rod nematics: structure and symmetries
topic Soft Condensed Matter
Materials Science
Chemical Physics
url https://arxiv.org/abs/2408.13325