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  1. Book ; Conference proceedings: Proceedings of the 12th European Conference on Liquid Crystals (ECLC 2013), Rhodes, Greece, September 22 - 27, 2013

    Vanakaras, Alexandros, G

    (Molecular crystals and liquid crystals ; 615.2015)

    2015  

    Event/congress ECLC (12, 2013.09.22-27, Rhodes) ; European Conference on Liquid Crystals (12, 2013.09.22-27, Rhodes)
    Author's details guest ed.: Alexandros G. Vanakaras
    Series title Molecular crystals and liquid crystals ; 615.2015
    Language English
    Size VI, 108 S.
    Publisher Taylor & Francis
    Publishing place Philadelphia, Pa
    Document type Book ; Conference proceedings
    Database Library catalogue of the German National Library of Science and Technology (TIB), Hannover

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  2. Book ; Conference proceedings: Proceedings of the 12th European Conference on Liquid Crystals (ECLC 2013), Rhodes, Greece, September 22 - 27, 2013

    Vanakaras, Alexandros, G

    (Molecular crystals and liquid crystals ; ...)

    2015  

    Title variant Twelfth
    Event/congress ECLC (12, 2013.09.22-27, Rhodes) ; European Conference on Liquid Crystals (12, 2013.09.22-27, Rhodes)
    Author's details guest ed.: Alexandros G. Vanakaras
    Series title Molecular crystals and liquid crystals
    ...
    Language English
    Publisher Taylor & Francis
    Publishing place Philadelphia, Pa
    Document type Book ; Conference proceedings
    Database Library catalogue of the German National Library of Science and Technology (TIB), Hannover

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  3. Article ; Online: Field-induced anti-nematic and biaxial ordering in binary mixtures of discotic mesogens and spherical magnetic nanoparticles.

    Peroukidis, Stavros D / Klapp, Sabine H L / Vanakaras, Alexandros G

    Soft matter

    2020  Volume 16, Issue 47, Page(s) 10667–10675

    Abstract: Using computer simulations we explore the equilibrium structure and response to external stimuli of complex magnetic hybrids consisting of magnetic particles in discotic liquid crystalline matrices. We show that the anisotropy of the liquid crystalline ... ...

    Abstract Using computer simulations we explore the equilibrium structure and response to external stimuli of complex magnetic hybrids consisting of magnetic particles in discotic liquid crystalline matrices. We show that the anisotropy of the liquid crystalline matrix (either in the nematic or in the columnar phase) promotes the collective orientational ordering of self-assembled magnetic particles. Upon applying an external homogeneous magnetic field in an otherwise isotropic state, the magnetic particles self-assemble into linear-rodlike-chains. At the same time structural changes occur in the matrix. The matrix transforms from an isotropic to a non-conventional anti-nematic state in which the symmetry axis of the discs is, on average, perpendicular to the magnetic field. In addition, a stable biaxial nematic state is found upon applying an external field to an otherwise uniaxial discotic nematic state. These observed morphologies constitute an appealing alternative to binary mixtures of rigid rod-disc system and indicate that non-trivial biaxial ordering can be obtained in the presence of a uniaxial external stimulus.
    Language English
    Publishing date 2020-06-30
    Publishing country England
    Document type Journal Article
    ZDB-ID 2191476-X
    ISSN 1744-6848 ; 1744-683X
    ISSN (online) 1744-6848
    ISSN 1744-683X
    DOI 10.1039/d0sm01366h
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: Self-organisation of fullerene-containing conical supermesogens.

    Peroukidis, Stavros D / Vanakaras, Alexandros G / Photinos, Demetri J

    Soft matter

    2020  Volume 4, Issue 3, Page(s) 493–499

    Abstract: A molecular model of cubic building blocks is used to describe the mesomorphism of conical fullerenomesogens. Calculations based on density functional molecular theory and on Monte Carlo computer simulations give qualitatively similar results that are ... ...

    Abstract A molecular model of cubic building blocks is used to describe the mesomorphism of conical fullerenomesogens. Calculations based on density functional molecular theory and on Monte Carlo computer simulations give qualitatively similar results that are also in good agreement with the experimentally observed mesomorphic behaviour. The columnar and lamellar mesophases obtained are non-polar, and their relative stability is controlled by a single model parameter representing the softness of the repulsive interactions among the building blocks of the conical molecules.
    Language English
    Publishing date 2020-09-07
    Publishing country England
    Document type Journal Article
    ZDB-ID 2191476-X
    ISSN 1744-6848 ; 1744-683X
    ISSN (online) 1744-6848
    ISSN 1744-683X
    DOI 10.1039/b714506c
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: Dipole-dipole correlations in the nematic phases of symmetric cyanobiphenyl dimers and their binary mixtures with 5CB.

    Zavvou, Evangelia E / Ramou, Efthymia / Ahmed, Ziauddin / Welch, Chris / Mehl, Georg H / Vanakaras, Alexandros G / Karahaliou, Panagiota K

    Soft matter

    2023  Volume 19, Issue 47, Page(s) 9224–9238

    Abstract: We report on the temperature dependence of birefringence and of the static dielectric permittivity tensor in a series of binary mixtures between the symmetric, bent-shaped, 1'',9''-bis(4-cyanobiphenyl-4'-yl)nonane (CB9CB) dimer and the monomeric ... ...

    Abstract We report on the temperature dependence of birefringence and of the static dielectric permittivity tensor in a series of binary mixtures between the symmetric, bent-shaped, 1'',9''-bis(4-cyanobiphenyl-4'-yl)nonane (CB9CB) dimer and the monomeric nematogen 5CB. In the studied composition range the mixtures exhibit two nematic phases with distinct birefringence and dielectric features. Birefringence measurements are used to estimate the temperature dependence of the tilt between the axis defining the nanoscale helical modulation of the low temperature nematic phase with the (local) direction of the maximal alignment of the cyanobiphenyl units. Planar as well as magnetically and/or electrically aligned samples are used to measure the perpendicular and parallel components of the dielectric permittivity in both nematic phases. A self-consistent molecular field theory that takes into account flexibility and symmetry of the constituent mesogens is introduced for the calculation of order parameters and intra-molecular orientational dipolar correlations of the flexible dimers as a function of temperature/concentration. Utilising the tilt angle, as calculated from the birefringence measurements, and the predictions of the molecular theory, dielectric permittivity is modelled in the framework of the anisotropic version of the Kirkwood-Fröhlich theory. Using the inter-molecular Kirkwood correlation factors as adjustable parameters, excellent agreement between theory and permittivity measurements across the whole temperature range and composition of the mixtures is obtained. The importance of the orientational, intra- and inter-molecular, dipolar correlations, their relative impact on the static dielectric properties, as well as their connection with the local structure of the nematic phases of bent-shaped bimesogens, is discussed.
    Language English
    Publishing date 2023-12-06
    Publishing country England
    Document type Journal Article
    ZDB-ID 2191476-X
    ISSN 1744-6848 ; 1744-683X
    ISSN (online) 1744-6848
    ISSN 1744-683X
    DOI 10.1039/d3sm01017a
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: Homogeneous alignment of liquid crystalline dendrimers confined in a slit-pore. A simulation study.

    Workineh, Zerihun G / Vanakaras, Alexandros G

    Journal of physics. Condensed matter : an Institute of Physics journal

    2016  Volume 28, Issue 11, Page(s) 115002

    Abstract: In this work we present results from isobaric-isothermal (NPT) Monte Carlo simulation studies of model liquid crystalline dendrimer (LCDr) systems confined in a slit-pore made of two parallel flat walls. The dendrimers are modelled as a collection of ... ...

    Abstract In this work we present results from isobaric-isothermal (NPT) Monte Carlo simulation studies of model liquid crystalline dendrimer (LCDr) systems confined in a slit-pore made of two parallel flat walls. The dendrimers are modelled as a collection of spherical and ellipsoidal particles corresponding to the junction points of the dendritic core and to the mesogenic units respectively. Assuming planar uniform (unidirectional) soft anchoring of the mesogenic units on the substrates we investigate the conformational and alignment properties of the LCDr system at different thermodynamic state points. Tractable coarse grained force fields have been used from our previous work. At low pressures the interior of the pore is almost empty, since almost all LCDrs are anchored to the substrates forming two-dimensional smectic-like structures with the mesogens aligned along the aligning direction of the substrates. As the pressure grows the LCDrs occupy the whole pore. However, even at low temperatures, the smectic organization does not transmit in the interior of the pore and is preserved for distances of 2-3 mesogenic diameters from the walls. For this reason, the global orientational order decreases with increasing pressure (density). In the vicinity (2-3 mesogenic diameters) of the pore walls, mesogenic units preserve the smectic structure whose layers are separated by layers of spherical beads. In this region individual LCDrs possess a rod like shape.
    Language English
    Publishing date 2016-03-23
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 1472968-4
    ISSN 1361-648X ; 0953-8984
    ISSN (online) 1361-648X
    ISSN 0953-8984
    DOI 10.1088/0953-8984/28/11/115002
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  7. Article ; Online: A molecular theory of nematic-nematic phase transitions in mesogenic dimers.

    Vanakaras, Alexandros G / Photinos, Demetri J

    Soft matter

    2016  Volume 12, Issue 7, Page(s) 2208–2220

    Abstract: We study theoretically the molecular origins of the fascinating, and still debated, nematic-nematic phase transition exhibited by symmetric, statistically achiral, mesogenic dimers. A simple molecular model that mimics the key features and symmetry (C2V) ...

    Abstract We study theoretically the molecular origins of the fascinating, and still debated, nematic-nematic phase transition exhibited by symmetric, statistically achiral, mesogenic dimers. A simple molecular model that mimics the key features and symmetry (C2V) of this class of mesogens is presented. In the mean-field approximation, the model yields up to three positionally disordered phases, one isotropic and two nematic. The low temperature nematic phase (NX) has a local two-fold symmetry axis, which is also a direction of molecular polar ordering and is tightly twisted about a macroscopic phase axis. The onset of polar ordering generates spontaneous chiral symmetry breaking and the formation of chiral domains of opposite handedness, manifested primarily by the twisting of the polar director. Within these domains the statistical balance between the enantiomer conformations is slightly shifted and the principal axes of the ordering tensors of the molecular segments twist at constant tilt angles with the helical axis. Key experimental results on the NX phase of liquid crystalline dimers are discussed in the light of the theoretical predictions of the model, which are also contrasted with the predictions of the twist-bend nematic model.
    Language English
    Publishing date 2016-02-21
    Publishing country England
    Document type Journal Article
    ZDB-ID 2191476-X
    ISSN 1744-6848 ; 1744-683X
    ISSN (online) 1744-6848
    ISSN 1744-683X
    DOI 10.1039/c5sm02505b
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  8. Article: All Structures Great and Small: Nanoscale Modulations in Nematic Liquid Crystals.

    Samulski, Edward T / Reyes-Arango, Denisse / Vanakaras, Alexandros G / Photinos, Demetri J

    Nanomaterials (Basel, Switzerland)

    2021  Volume 12, Issue 1

    Abstract: The nature of the nanoscale structural organization in modulated nematic phases formed by molecules having a nonlinear molecular architecture is a central issue in contemporary liquid crystal research. Nevertheless, the elucidation of the molecular ... ...

    Abstract The nature of the nanoscale structural organization in modulated nematic phases formed by molecules having a nonlinear molecular architecture is a central issue in contemporary liquid crystal research. Nevertheless, the elucidation of the molecular organization is incomplete and poorly understood. One attempt to explain nanoscale phenomena merely "shrinks down" established macroscopic continuum elasticity modeling. That explanation initially (and mistakenly) identified the low temperature nematic phase (
    Language English
    Publishing date 2021-12-29
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 2662255-5
    ISSN 2079-4991
    ISSN 2079-4991
    DOI 10.3390/nano12010093
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  9. Book ; Online: The Twist Bend Nematic

    Samulski, Edward T. / Vanakaras, Alexandros G. / Photinos, Demetri J.

    A Case of Mistaken Identity

    2020  

    Abstract: We review the physics underlying Meyer's conjecture of how macroscopic-scale twist and bend conspire within the Frank-Oseen elasticity theory of nematics to create a heliconical arrangement of the uniaxial, apolar nematic director, the so-called "twist ... ...

    Abstract We review the physics underlying Meyer's conjecture of how macroscopic-scale twist and bend conspire within the Frank-Oseen elasticity theory of nematics to create a heliconical arrangement of the uniaxial, apolar nematic director, the so-called "twist bend nematic" $\rm N_{TB}$. We show that since 2011 a second, lower-temperature nematic phase observed in odd methylene-linked cyanobiphenyl dimers discovered by Toriumi and called $\rm N_X$, has been incorrectly identified as $\rm N_{TB}$. Moreover, as more quantitative data on the $\rm N_X$ emerged, Meyer's simple prediction has been distorted to accommodate those findings. In fact, the molecular organization in the $\rm N_X$ conforms to the $\rm N_{PT}$ phase, a polar, twisted arrangement of nonlinear mesogens advanced in 2016. The attributes of the $\rm N_{PT}$ are summarized and differentiated from those of the $\rm N_{TB}$ in an effort to contribute to a better understanding of the $\rm N_X$ phase and, equally important, to encourage researchers to continue to search for a liquid crystal that exhibits Meyer's pioneering theoretical suggestion, namely that form-chirality can exist in simple nematics composed of achiral molecules.

    Comment: 10 pages, 2 figures
    Keywords Condensed Matter - Soft Condensed Matter
    Subject code 612
    Publishing date 2020-05-29
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

    Full text online

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  10. Article ; Online: Polar Molecular Ordering in the N

    Kumar, Anant / Vanakaras, Alexandros G / Photinos, Demetri J

    The journal of physical chemistry. B

    2017  

    Abstract: The potential of mean torque governing the orientational ordering of prochiral solutes in the two nematic phases (N and ... ...

    Abstract The potential of mean torque governing the orientational ordering of prochiral solutes in the two nematic phases (N and N
    Language English
    Publishing date 2017-11-17
    Publishing country United States
    Document type Journal Article
    ISSN 1520-5207
    ISSN (online) 1520-5207
    DOI 10.1021/acs.jpcb.7b08319
    Database MEDical Literature Analysis and Retrieval System OnLINE

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