Thermotropic reentrant isotropic symmetry and induced smectic antiferroelectricity in the ferroelectric nematic material RM734.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 40249786.
- Also identified by DOI 10.1073/pnas.2424917122 and PMC identifier 12036992.
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Abstract
We report a transition from the ferroelectric nematic liquid crystal (N<sub>F</sub>) phase to a lower-temperature, apolar fluid phase having reentrant isotropic symmetry (I<sub>R</sub>), in the liquid crystal compound RM734 doped with small concentrations of the ionic liquids 1-Butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF<sub>6</sub>) or 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM-TFSI). Even a trace amount of ionic liquid dopant facilitates the kinetic pathway for the transition from the N<sub>F</sub> to the I<sub>R</sub>, enabling simple cooling to produce this isotropic fluid phase rather than resulting in immediate crystallization. The I<sub>R</sub> was also obtained in the absence of specific ionic liquid doping by appropriate temperature cycling in three distinct, as-synthesized-and-purified batches of RM734, two commercial and one from our laboratory. Ionic liquid doping also stabilizes the smectic Z<sub>A</sub>, an additional birefringent antiferroelectric phase having the director parallel to fluid smectic layers, significantly increasing its temperature range between the paraelectric and ferroelectric nematic phases with increasing BMIM concentration.