Entropy stabilized form chirality in curved rod nematics: structure and symmetries.
basic_science · Level V
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- Record sourced from PubMed, PMID 39847047.
- Also identified by DOI 10.1039/d4sm01229a.
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Abstract
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, <i>C</i><sub>2</sub>-symmetry axis that tightly spirals generating a mirror-symmetry-breaking organization 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 "N<sub>X</sub> phase" found in CB7CB dimers.