Observation of a uniaxial ferroelectric smectic A phase.
basic_science · Level V
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- Record sourced from PubMed, PMID 36375062.
- Also identified by DOI 10.1073/pnas.2210062119 and PMC identifier 9704750.
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Abstract
We report the observation of the smectic A<sub>F</sub>, a liquid crystal phase of the ferroelectric nematic realm. The smectic A<sub>F</sub> is a phase of small polar, rod-shaped molecules that form two-dimensional fluid layers spaced by approximately the mean molecular length. The phase is uniaxial, with the molecular director, the local average long-axis orientation, normal to the layer planes, and ferroelectric, with a spontaneous electric polarization parallel to the director. Polarization measurements indicate almost complete polar ordering of the ∼10 Debye longitudinal molecular dipoles, and hysteretic polarization reversal with a coercive field ∼2 × 10<sup>5</sup> V<i>/</i>m is observed. The SmA<sub>F</sub> phase appears upon cooling in two binary mixtures of partially fluorinated mesogens: 2N/DIO, exhibiting a nematic (N)-smectic Z<sub>A</sub> (SmZ<sub>A</sub>)-ferroelectric nematic (N<sub>F</sub>)-SmA<sub>F</sub> phase sequence, and 7N/DIO, exhibiting an N-SmZ<sub>A</sub>-SmA<sub>F</sub> phase sequence. The latter presents an opportunity to study a transition between two smectic phases having orthogonal systems of layers.