Conventional and unconventional ionic phenomena in tunable soft materials made of liquid crystals and nanoparticles

Garbovskiy, Yuriy

doi:10.1088/2632-959x/abe652

Cited by 38 publications

(34 citation statements)

References 225 publications

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“…To achieve a comparable screening charge 𝜌 𝑓 ~𝑒𝑛~(0.2 − 0.9) × 10 4 𝐶/𝑚 3 , where 𝑒 = 1.6 × 10 −19 𝐶 is the elementary charge, the concentration of ions at the DW should be 𝑛~(10 22 − 10 23 )/𝑚 3 . A high ion concentration 𝑛~10 23 /𝑚 3 has been reported as a volumeaveraged value for ferroelectric smectics 32 , although conventional nematics usually yield smaller values 33 , 𝑛~(10 20 − 10 22 )/𝑚 3 . It is reasonable to assume that even when the volume-averaged 𝑛 is less than 𝑛~(10 22 − 10 23 )/𝑚 3 , mobile charges could move from the uniform regions of the material and accumulate at local concentrations sufficient to screen the splay-induced polarization charge.…”

Section: Resultsmentioning

confidence: 99%

Soliton walls paired by polar surface interactions in a ferroelectric nematic liquid crystal

et al. 2022

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Surface interactions are responsible for many properties of condensed matter, ranging from crystal faceting to the kinetics of phase transitions. Usually, these interactions are polar along the normal to the interface and apolar within the interface. Here we demonstrate that polar in-plane surface interactions of a ferroelectric nematic NF produce polar monodomains in micron-thin planar cells and stripes of an alternating electric polarization, separated by $${180}^{{{{{{\rm{o}}}}}}}$$ 180 o domain walls, in thicker slabs. The surface polarity binds together pairs of these walls, yielding a total polarization rotation by $${360}^{{{{{{\rm{o}}}}}}}$$ 360 o . The polar contribution to the total surface anchoring strength is on the order of 10%. The domain walls involve splay, bend, and twist of the polarization. The structure suggests that the splay elastic constant is larger than the bend modulus. The $${360}^{{{{{{\rm{o}}}}}}}$$ 360 o pairs resemble domain walls in cosmology models with biased vacuums and ferromagnets in an external magnetic field.

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Section: Resultsmentioning

confidence: 99%

Soliton walls paired by polar surface interactions in a ferroelectric nematic liquid crystal

et al. 2022

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“…Regardless the type of application, information about ions in thermotropic liquid crystals is very important. This information can be obtained by performing electrical characterization of liquid crystal materials [27,28,29 and references therein]. The obtained experimental results can be used to evaluate DC electrical conductivity, ion mobility and ion concentration in liquid crystals [30,31,32].…”

Section: Introductionmentioning

confidence: 99%

Steady-State and Transient Electrical Properties of Liquid Crystal Cells

Garbovskiy

Webb

2022

The 3rd International Online Conference on Crystals

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Rapidly expanding and new applications of liquid crystal materials cover a wide range of technology products. A very incomplete list includes conventional and miniature high-resolution displays, AR/VR glasses, smart windows, dynamic lenses, tunable filters and retarders, electrically controlled sensors, reconfigurable antennas for wireless and space communications, and many other commercially available devices. The aforementioned devices are enabled by the collective reorientation of thermotropic molecular liquid crystals under the action of applied electric fields. The reorientation effects in liquid crystals can be altered by ionic contaminants typically present in mesogenic materials in small quantities. Therefore, information about ions in liquid crystals is very important because it allows for a proper selection of liquid crystal materials and uncompromised performance of liquid crystal devices. This information can be obtained by performing electrical measurements of liquid crystal materials. Measurements of basic electrical parameters (DC conductivity, charge mobility and ion density) are carried out using sandwich-like liquid crystal cells of finite thickness. Once a cell is filled with liquid crystal materials, interactions between ions and the cell substrates will result in the time dependence of the ion density and DC electrical conductivity until a steady state is reached. In this paper, we show how complementary information about ionic processes in liquid crystal cells can be obtained by analyzing their transient and steady state electrical properties.

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“…Based on their ordered structure, carbon nanotubes (CNTs) offer many fascinating properties like polarization, high dielectric constant, etc., that could be utilized in various mechanical and electronic devices [11][12][13][14]. During the last two decades, the physical interactions between the LCs and CNTs has obtained an immense research interest worldwide [15][16][17][18][19][20]. The addition of small amount of CNTs into the LCs could lead to some fascinating phenomena.…”

Section: Introductionmentioning

confidence: 99%

Carbon Nanotubes Blended Nematic Liquid Crystal for Display and Electro-Optical Applications

Singh

Sikarwar

Pandey³

et al. 2021

Electronic Materials

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In this paper, we investigate a commercial nematic liquid crystal (LC) mixture namely E7 dispersed with small concentrations of multi-walled carbon nanotubes (MWCNTs). The dielectric and electro-optical characterizations have been carried out in the homogeneously and vertically aligned LC cells. The electro-optical response of LC molecules has been enhanced by 60% after the addition of MWCNTs, which is attributed to the reduced rotational viscosity in the composites. MWCNTs act like barricades for ionic impurities by reducing them up to ∼34.3% within the dispersion limit of 0.05 wt%. The nematic–isotropic phase transition temperature (TNI) of the E7 LC has also been shifted towards the higher temperature, resulting in a more ordered nematic phase. The enhanced birefringence and orientational order parameter in the LC-MWCNTs are attributed to π-π electron stacking between the LC molecules and the MWCNTs. The outlined merits of the LC-MWCNTs composites evince their suitability for ultrafast nematic-based electro-optical devices.

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Conventional and unconventional ionic phenomena in tunable soft materials made of liquid crystals and nanoparticles

Cited by 38 publications

References 225 publications

Soliton walls paired by polar surface interactions in a ferroelectric nematic liquid crystal

Soliton walls paired by polar surface interactions in a ferroelectric nematic liquid crystal

Steady-State and Transient Electrical Properties of Liquid Crystal Cells

Carbon Nanotubes Blended Nematic Liquid Crystal for Display and Electro-Optical Applications

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