Carbonyl- and thioether-linked cyanobiphenyl-based liquid crystal dimers exhibiting twist-bend nematic phases

Tetrahedron ◽  
2020 ◽  
pp. 131870
Author(s):  
Yuki Arakawa ◽  
Kenta Komatsu ◽  
Yuko Ishida ◽  
Kazunobu Igawa ◽  
Hideto Tsuji
Keyword(s):  
Liquid Crystal ◽  
Nematic Phases

Liquid Crystal Trimers Incorporating Saturated Isosteres of Benzene and Exhibiting Modulated Nematic Phases

2019 ◽  
Author(s):  
Adam Al-Janabi ◽  
Richard Mandle
Keyword(s):  
Liquid Crystal ◽  
Helical Structure ◽  
Molecular Shape ◽  
Saturated Hydrocarbons ◽  
Fluid System ◽  
Structural Requirement ◽  
Disubstituted Benzene ◽  
Bona Fide ◽  
Nematic Phases ◽  
Bend Angles

<p>The nematic twist-bend (N<sub>TB</sub>) liquid crystal phase possesses a local helical structure with a pitch length of a few nanometres and is the first example of spontaneous symmetry breaking in a fluid system. All known examples of the N­<sub>TB­</sub> phase occur in materials whose constituent mesogenic units are aromatic hydrocarbons. It is not clear if this is due to synthetic convenience or a <i>bona fide</i> structural requirement for a material to exhibit this phase of matter. In this work we demonstrate that materials consisting largely of saturated hydrocarbons could also give rise to this mesophase. Furthermore, replacement of 1,4-disubstituted benzene with <i>trans</i> 1,4-cyclohexane or even 1,4-cubane does not especially alter the transition temperatures of the resulting material nor does it appear to impact upon the heliconical tilt angle, suggesting the local structure of the phase is unperturbed. Calculating the probability distribution of bend angles reveals that the choice of isosteric group has little impact on the overall molecular shape, demonstrating the shape-driven nature of the N<sub>TB</sub> phase. </p>

Liquid Crystal Behavior of V2O5·nH2O Gels

1998 ◽  
Vol 547 ◽  
Author(s):  
J. Livage ◽  
P. Davidson ◽  
X. Commeinhes ◽  
O. Pelletier
Keyword(s):  
Liquid Crystal ◽  
Vanadium Pentoxide ◽  
Colloidal Particles ◽  
Organic Molecules ◽  
Polarized Light ◽  
Colloidal Suspensions ◽  
Acid Dissociation ◽  
Polymeric Particles ◽  
Nematic Phases ◽  
Electrostatic Repulsions

AbstractMost liquid crystals are made of organic molecules, very few of them are based on mineral compounds. Vanadium pentoxide gels and sols have been shown to give mesophases. They are made of ribbon-like polymeric particles of vanadium pentoxide dispersed in water. Ansitropic xerogel layers are formed when these gels are deposited and dried onto flat substrates. Dehydration is reversible and fluid phases are again obtained via a swelling process when water is added to the xerogel.When observed by polarized light microscopy, colloidal suspensions of V2O5 ribbons display defects typical of lyotropic nematic phases. Dilute nematic suspensions can even be oriented by applying a magnetic field of about 0.5 Tesla. Such a liquid crystal behavior is mainly due to the highly anisotropic shape of vanadium oxide colloidal particles. Acid dissociation at the oxide/water interface gives rise to surface electrical charges and electrostatic repulsions should also be responsible for the stabilization of the nematic phase.

scholarly journals Study of Orientational Order of Liquid Crystal 8 OCB Doped with Perylene-like Dyes by Means of Polarized Optical Spectroscopy

1996 ◽  
Vol 51 (12) ◽  
pp. 1192-1196 ◽  
Author(s):  
Danuta Bauman ◽  
Eryk Wolarz
Keyword(s):  
Liquid Crystal ◽  
Fluorescence Spectra ◽  
Orientational Order ◽  
Smectic A ◽  
Orientational Distribution ◽  
Nematic Phases ◽  
Polarized Optical Spectroscopy ◽  
Parameter Values ◽  
Orientational Distribution Function ◽  
Orientation Of Molecules

Abstract Measurements of the polarized absorption and fluorescence spectra for perylene-like dyes dis-solved in a liquid crystal 8 OCB have been used to study the long-range orientational order in the smectic A and nematic phases. The temperature dependence of the order parameters <P2> and <P4> has been investigated and the orientational distribution function has been determined. On the basis of the experimental order parameter values some information about the orientation of molecules in guest-host mixtures has been obtained.

scholarly journals Methylene- and thioether-linked cyanobiphenyl-based liquid crystal dimers CBnSCB exhibiting room temperature twist-bend nematic phases and glasses

2021 ◽  
Vol 2 (5) ◽  
pp. 1760-1773
Author(s):  
Yuki Arakawa ◽  
Kenta Komatsu ◽  
Takuma Shiba ◽  
Hideto Tsuji
Keyword(s):  
Liquid Crystal ◽  
Homologous Series ◽  
Room Temperature ◽  
Nematic Phases

A homologous series of methylene- and thioether-linked cyanobiphenyl-based liquid crystal dimers, CBnSCB, was developed and found to exhibit stable twist-bend nematic (NTB) phases, which undergo vitrification to give NTB glass phases.

scholarly journals Mesomorphism Dependence on Molecular Flexibility at Constant Rigidity

2015 ◽  
Vol 50 ◽  
pp. 1-8
Author(s):  
D.T. Pidwani ◽  
G.N. Bhola ◽  
Umed C. Bhoya
Keyword(s):  
Thermal Stability ◽  
Liquid Crystal ◽  
Homologous Series ◽  
Molecular Structures ◽  
Smectic A ◽  
Crystal Properties ◽  
Smectic Mesophase ◽  
High Transition ◽  
Nematic Phases ◽  
Optical Polarizing Microscopy

A Novel homologous series of high transition temperature RO-C6H4-CH=CH-COO-C6H4-N=CH-CH=CH-C6H5 has been synthesis and studied with a view to understand establish and evaluate the relation between liquid crystal properties and the molecular structure of a substance. A series consists of thirteen homologues. All the homologues are mesogenic. Smectic mesophase commences from C12 to C18 homologues. Nematic mesophase appears from C1 to C18 homologues. The textures of a nematic phases are of threaded or schlieren and that of the smectic phase are focal conic fan shaped of smectic-A or C type. Transition temperatures and textures were determined by an optical polarizing microscopy equipped with a heating stage. The analytical and spectral data confirms the molecular structures of homologues. Thermal stability for smectic and nematic are 118.5 0C and 224.77 °C, whose total mesophase length ranger from 73.0 °C to 111 °C. The liquid crystal properties from homologue to homologue varies in the same series. Some liquid crystal properties of present series are compared with the structurally similar known homologous series. Present novel homologous series is partly smectogenic and fully nematogenic and of higher ordered melting type and high thermal stability

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