Carbon nanotubes doped liquid crystals: Robust composites with a function of electro-optic memory

Yaroshchuk, O.; Tomylko, S.; Dolgov, L.; Semikina, T.V.; Koval’chuk, A. V.

doi:10.1016/j.diamond.2010.01.022

Cited by 19 publications

(5 citation statements)

References 24 publications

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“…Subsection 4.2 is based on our original results concerning the irreversible electro-optical response of the LC-CNTs systems named as electro-optic memory Dolgov et al, 2008a). At last, subsection 4.3 describes enhancement of the memory effect in the systems with induced chirality (Yaroshchuk et al, 2010).…”

Section: Electro-optic Studies Of Lc-cnts Compositesmentioning

confidence: 99%

Liquid Crystal Dispersions of Carbon Nanotubes: Dielectric, Electro-Optical and Structural Peculiarities

Dolgov¹,

Koval’chuk²,

Lebovka³

et al. 2010

Carbon Nanotubes

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A present chapter is focused on remarkable dielectric, electro-optical and micro-structural peculiarities of LC-CNTs dispersions, their correlation and mutual influence. It is mainly based on authors' original results obtained within recent years. The structure of this chapter is the following. The introductory part (section 1) gives short introduction to LC-CNTs composites and elucidates benefit of combination of LC and CNTs. It also outlines a field of questions further considered. A section 2 gives details of our samples and experimental methods. The next three sections correspondingly consider dielectric, electro-optical and structural peculiarities of LC-CNTs composites. Each of these topical sections starts with a short review and lasts with the authors' original results. The final, conclusion part (Section 6), summarizes most interesting properties of LC-CNTs suspensions, their application perspectives and mention some exciting problems for further investigations. www.intechopen.com Liquid crystal dispersions of carbon nanotubes: dielectric, electro-optical and structural peculiarities 453 power of 150 W. The concentration of CNTs, c, was varied in the range 0-2 wt %. Doping of CNTs has not influenced essentially the phase transition temperatures of LC-CNTs composites. 2.4 Cells The cells for electro-optical and dielectric measurements were made from glass substrates containing patterned ITO electrodes and aligning layers of polyimide. The polyimides AL2021 (JSR, Japan) and SE5300 (Nissan Chemicals, Japan) were used for homeotropic alignment of LC EBBA, MLC6608 and MLC6609, while the polyimide SE150 (Nissan Chemicals, Japan) was utilized for planar alignment of LC 5CB. The polyimide layers were rubbed by a fleecy cloth in order to provide a uniform planar alignment of LC in either fieldon state (EBBA, MLC6608 and MLC6609) or a zero field (5CB). The cells were assembled so that the rubbing directions of the opposite aligning layers were antiparallel. A cell gap was maintained by the glass spacers of appropriate size (16 m, if not otherwise stated). Finally, these cells were filled capillary with neat or CNTs doped liquid crystals heated to isotropic state. In some dielectric measurements the cells without alignment layers were utilized. The structure of LC-CNTs composites was monitored by observation of the filled cells placed between crossed polarizers, both by naked eye and in an optical polarizing microscope. 2.5 Electro-optical measurements The electro-optical measurements were carried out using the experimental setup described in (Koval'chuk et al., 2001a). The cell was set between two crossed polarizers so that the angle between the polarizer axes and the rubbing direction was 45°. The sinusoidal voltage 0-60 V (at frequency f=2 kHz) was applied to the cell. The voltage was stepwise increased from 0 to 60 V and then decreased back to 0; the total measuring time, i.e., time of voltage application, was about 1 min. The transmittance of the samples was calculated as =(I out /I in)*100%, where I in and ...

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Section: Electro-optic Studies Of Lc-cnts Compositesmentioning

confidence: 99%

Liquid Crystal Dispersions of Carbon Nanotubes: Dielectric, Electro-Optical and Structural Peculiarities

Dolgov¹,

Koval’chuk²,

Lebovka³

et al. 2010

Carbon Nanotubes

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“…The efficiency of electro-optical memory was depended on the concentration of MWCNTs, C, and reached its maximum at C = 0.02-0.05 wt%. This effect was even stronger when the nematic matrix was additionally doped with a small quantity of chiral dopant, which stabilized the planar texture [189]. The observed data were explained accounting for possible stabilization of the planar state of LC by the network of CNTs formed upon the disintegration of aggregates under the action of electro-hydrodynamic fluxes [188].…”

Section: Electro-optical Applications and Memory Effectsmentioning

confidence: 82%

Carbon Nanotubes in Liquid Crystals: Fundamental Properties and Applications

Lisetski

Soskin

Lebovka

2015

Springer Proceedings in Physics

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The structure and properties of liquid crystalline suspensions filled by carbon nanotubes (CNTs) are critically reviewed. Special attention is paid to interactions between CNTs and molecules of the liquid crystals (LC), which lead to formation of ordered supramolecular structures. These structures, in turn, determine unique physical properties of LC + CNT suspensions, including electrical conductivity, dielectric permittivity, phase transitions, optical transmission, memory effects that can be used in electrooptic and optoelectronic devices, etc. Great variety of LC phases are considered as a host media, such as nematics, cholesterics, smectics of different types (including ferroelectrics), lyotropic, chromonic, ionic and hydrogen-bonded liquid crystals. Alongside multi-and single-walled carbon nanotubes, the suspensions can also contain the platelets of organoclays used for facilitation of CNT dispersing. Recent practical applications of LC + CNT suspensions and nanomaterials based thereon are also outlined.

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“…The use of carbon nanotubes (CNTs) as LC dopant has improved their switching responses, nonvolatile memory effects, diffractive properties and threshold voltage. [7][8][9][10][11] Their use is also found in protein biosensors, biocatalysts, bio separators and for drug storage and delivery. [12] It has been reported that a small amount of CNT doping effectively reduces optical flicker, image sticking, parasitic backflow and associated optical bounce which are usually perceived as chronic problems with the LC cells.…”

Section: Introductionmentioning

confidence: 99%

Memory effects in chiral nematic liquid crystals doped with functionalised single-walled carbon nanotubes

2015

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Octadecylamine-functionalised single-walled carbon nanotubes (SWCNTs) were dispersed into nematic liquid crystals (LCs) doped with chiral molecules. The collective orientation of nematic LC molecules in helical layers was manipulated by varying dopant concentration. Highly anisotropic nature of SWCNTs enhanced the anisotropy of the LC as confirmed by polarised fluorescence spectroscopy. The π-π interaction of SWCNTs present in the planar alignment layers and twisted nematic LC molecules affects the molecular relaxation process. An irreversible electro-optic memory in the material has been observed.

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Carbon nanotubes doped liquid crystals: Robust composites with a function of electro-optic memory

Cited by 19 publications

References 24 publications

Liquid Crystal Dispersions of Carbon Nanotubes: Dielectric, Electro-Optical and Structural Peculiarities

Liquid Crystal Dispersions of Carbon Nanotubes: Dielectric, Electro-Optical and Structural Peculiarities

Carbon Nanotubes in Liquid Crystals: Fundamental Properties and Applications

Memory effects in chiral nematic liquid crystals doped with functionalised single-walled carbon nanotubes

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