Structural changes in the 6CHBT liquid crystal doped with spherical, rodlike, and chainlike magnetic particles

Kopčanský, P.; Tomašovičová, Natália; Koneracká, M.; Závišová, V.; Τimko, M.; Džarová, A.; Šprincová, Adriana; Éber, Nándor; Fodor‐Csorba, Katalin; Tóth-Katona, Tibor; Vajda, A.; Jadżyn, Jan

doi:10.1103/physreve.78.011702

Cited by 141 publications

(114 citation statements)

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“…The mean size of the spherical particles was 10 nm, while the mean size of the nanorods and chains of magnetosomes was 400 nm. As was shown in previous studies [9,16,21], the particle size and functionalization of the particles play an important role in the coupling between the magnetic moment of the magnetic particles and the director of the liquid crystal. The obtained results indicate that orientation of the magnetic moment and the director in both the cases (nanorods and chain-like particles) is parallel.…”

Section: Resultsmentioning

confidence: 96%

“…These dilute suspensions of magnetic particles based on nematic liquid crystals are called ferronematics. They have been intensively investigated in recent years both experimentally and theoretically [3][4][5][6][7][8][9][10][11][12][13][14][15][16]. The influence of the magnetic field on ferronematics depends on the coupling energy and mutual orientation of magnetic particles and liquid crystal molecules.…”

Section: Introductionmentioning

confidence: 99%

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Phase Transitions in Liquid Crystal Doped with Magnetic Particles of Different Shapes

et al. 2010

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In this study, observations of structural transitions in ferronematics based on the thermotropic nematic 4-trans-4 -n-hexyl-cyclohexyl-isothiocyanato-benzene (6CHBT) are described. Droplets of the nematic phase in the isotropic phase were observed in solutions of nematogenic 6CHBT dissolved in phenyl isocyanate and 6CHBT dissolved in phenyl isocyanate and doped with magnetic particles of different shapes (nanorods and chain-like particles). Magneto-dielectric measurements of structural transitions in these new systems enable to estimate of the type of anchoring of the nematic molecules on the magnetic particles surface.

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Section: Resultsmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Phase Transitions in Liquid Crystal Doped with Magnetic Particles of Different Shapes

et al. 2010

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“…The fact that oriented chains of MNPs inside a nematic LC stabilizes the host's ordering has been found in several experiments [3][4][5][6], and has also been theoretically analyzed by minimizing the elastic free energy [8]. The essential idea is that the presence of long magnetic chains enhances the strength of the local director field of the rods.…”

mentioning

confidence: 99%

“…Whereas the field sensitivity has been investigated and verified in many experiments [2][3][4][5][6][7][8], new interest was stimulated by the recent discovery of spontaneous magnetic ordering in a hybrid system of large, micron-sized magnetic plates embedded in a lyotropic nematic LC [9]. A crucial ingredient for the observed behavior are the LCmediated interactions stemming from local distortions of the LC director via the presence of the plates, whose size is much larger than that of the LC molecules.…”

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confidence: 99%

Spontaneous ordering of magnetic particles in liquid crystals: From chains to biaxial lamellae

Peroukidis

Klapp

2015

Phys. Rev. E

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Using Monte Carlo (MC) computer simulations we explore the self-assembly and ordering behavior of a hybrid, soft magnetic system consisting of small magnetic nano-spheres in a liquid-crystalline (LC) matrix. Inspired by recent experiments with colloidal rod-matrices we focus on conditions where the sphere and rod diameters are comparable. Already in the absence of a magnetic field, the nematic ordering of the LC can stabilize formation of magnetic chains along the nematic or smectic director, yielding a state with local (yet no macroscopic) magnetic order. The chains, in turn, increase the overall nematic order, reflecting the complex interplay of the structure formation of the two components. Increasing the sphere diameter the spontaneous uniaxial ordering is replaced by biaxial lamellar morphologies characterized by alternating layers of rods and magnetic chains oriented perpendicular to the rod's director. These novel ordering scenarios at zero field suggest complex response of the resulting hybrid to external stimuli such as magnetic fields and shear forces.Mixtures of magnetic nanoparticles (MNP) in liquidcrystalline (LC) matrices attract attention in fundamental physics and material science since about four decades ago: in 1970, Brochard and de Gennes [1] predicted, based on free energy considerations, various new effects including spontaneous magnetization in the liquid state, "compensated" phases and giant field-induced effects. Whereas the field sensitivity has been investigated and verified in many experiments [2][3][4][5][6][7][8], new interest was stimulated by the recent discovery of spontaneous magnetic ordering in a hybrid system of large, micron-sized magnetic plates embedded in a lyotropic nematic LC [9]. A crucial ingredient for the observed behavior are the LCmediated interactions stemming from local distortions of the LC director via the presence of the plates, whose size is much larger than that of the LC molecules. Indeed, LC-mediated elastic interactions and their consequences for colloidal self-assembly and ordering have intensively studied by experiments [10] and simulations [11,12] for many (non-magnetic) colloid/LC mixtures.In the present letter we focus on the opposite case of small MNPs in LC matrices, where the sizes are comparable and distortions of the LC do not play a significant role. An example of such systems are lyotropic suspensions of colloid pigment rods and magnetite MNPs which have been recently studied to investigate field-induced ordering effects [13, 14]. However, although there is strong interest in using such hybrids as new, stimuli-responsive or even adaptive materials [9], the microscopic structure of small MNPs in LC matrices is essentially unexplored; although this is clearly a prerequisite in terms of advancing new functionalities. Experimentally, the challenge is to actually "see" the relatively small MNPs with typical diameters of 10-15 nm; a solution of this problem might be provided by recently developed tomography techniques [15]. Suprisingly, however, the...

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“…NT alone cannot always provide the required parameters of LC. For example, to achieve sensitivity to the magnetic field there is a need to introduce magnetic nanoparticles (MN), too [7,8]. The question arises whether it is possible, knowing how each impurity acts separately on properties of liquid crystal, to predict the combined effect of nanoparticles at least of two types (MWNT and MN) on the LC properties.…”

Section: Introductionmentioning

confidence: 99%

Nonadditive changes in conductivity of micro PDLC under the influence of carbon nanotubes and magnetic nanoparticles

Kopčanský¹

2013

Semicond. Phys. Quantum Electron. Optoelectron.

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Abstract. Investigated in this work has been the effect of impurities -magnetic nanoparticles (MN) and multiwall carbon nanotubes (MWNT) -separately and together on morphology and dielectric properties of nematic liquid crystal 6CHBT dispersed in polyvinyl alcohol (PDLC). It has been shown that the nanoparticles and nanotubes together change the morphology of PDLC practically in the same manner as every type of impurity singly. The impurities influence also additively on the permittivity at low frequencies and electron component of the conductivity in the polymer matrix. We have found that when MN and MWNT act jointly their ion component of the conductivity exceeds the total changes in conductivity by six times greater than when each type of impurity acts singly. The most probable reason for this nonadditive change in conductivity can be aggregation of these nanoparticles.Keywords: magnetic nanoparticle, multiwall carbon nanotube, permittivity, ion component of the conductivity, electron component of the conductivity, polymer matrix.Manuscript received 25.06.13; revised version received 28.08.13; accepted for publication 23.10.13; published online 16.12.13.

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Structural changes in the 6CHBT liquid crystal doped with spherical, rodlike, and chainlike magnetic particles

Cited by 141 publications

References 9 publications

Phase Transitions in Liquid Crystal Doped with Magnetic Particles of Different Shapes

Phase Transitions in Liquid Crystal Doped with Magnetic Particles of Different Shapes

Spontaneous ordering of magnetic particles in liquid crystals: From chains to biaxial lamellae

Nonadditive changes in conductivity of micro PDLC under the influence of carbon nanotubes and magnetic nanoparticles

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