Mesomorphic property and orientational order in the nematic phases of nickel(II) and oxovanadium(IV) complexes of N-salicylidene-n-propylamine derivatives

1991 ◽  
Vol 30 (15) ◽  
pp. 3091-3096 ◽  
Author(s):  
Naomi. Hoshino ◽  
Akira. Kodama ◽  
Tomoko. Shibuya ◽  
Yoshio. Matsunaga ◽  
Seiichi. Miyajima
Keyword(s):  
Orientational Order ◽  
Mesomorphic Property ◽  
Nematic Phases

scholarly journals Raman scattering studies of order parameters in liquid crystalline dimers exhibiting the nematic and twist-bend nematic phases

2015 ◽  
Vol 3 (38) ◽  
pp. 10007-10016 ◽  
Author(s):  
Zhaopeng Zhang ◽  
Vitaly P. Panov ◽  
Mamatha Nagaraj ◽  
Richard J. Mandle ◽  
John W. Goodby ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Raman Scattering ◽  
Homologous Series ◽  
Liquid Crystalline ◽  
Orientational Order ◽  
Order Parameters ◽  
Polarized Raman Spectroscopy ◽  
Nematic Phases ◽  
Polarized Raman

The work deduces orientational order parameters in the nematic and twist-bend nematic phases. An homologous series of dimers is studied using Polarized Raman Spectroscopy.

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 Electro-induced orientational ordering of anisotropic pigment nanoparticles

2013 ◽  
Vol 371 (1988) ◽  
pp. 20120257 ◽  
Author(s):  
Robert J. Greasty ◽  
Robert M. Richardson ◽  
Susanne Klein ◽  
David Cherns ◽  
Michael R. Thomas ◽  
...  
Keyword(s):  
Electric Fields ◽  
Orientational Order ◽  
Optical Response ◽  
Pigment Particle ◽  
X Ray ◽  
X Ray Scattering ◽  
Orientational Ordering ◽  
Nematic Phases ◽  
High Concentrations ◽  
Ray Scattering

The response of anisotropic pigment particle suspensions to externally applied electric fields has been explored for possible application in reflective display technologies. Three different types of pigment particle were suspended in dodecane, using a polymeric stabilizer, and showed Schlieren textures between crossed polarizers at high concentrations (greater than 25–30 wt%), indicating the formation of colloidal nematic phases. Orientational order parameters were determined by X-ray scattering, and the influence of polydispersity on the values is discussed. X-ray scattering measurements also demonstrated a change in the structure factor consistent with the onset of a colloidal nematic phase. In addition, the pigment particles were dispersed into various liquid crystal hosts at low concentrations (less than 5 wt%) with and without the presence of mesogenic mimic stabilizers. However, the influence of these stabilizers on orientational ordering could not be confirmed. The electro-induced ordering determined via scattering was related to the electro-optical response of each suspension using a simple model. The particles in nematic hosts not only showed a high degree of orientational ordering at lower electric field strengths, but also showed a reduction in stability. Although these systems have shown strong orientational ordering, the optical response has been limited by the intrinsic shape of the pigment particles and the distribution of the transition dipoles moments within them. Nevertheless, the feasibility of developing materials for display applications has been demonstrated.

Orientational order of biaxial solutes in nematic phases Size and shape effects

1988 ◽  
Vol 3 (4) ◽  
pp. 485-505 ◽  
Author(s):  
M. Y. Kok ◽  
A. J. van der Est ◽  
E. E. Burnell
Keyword(s):  
Orientational Order ◽  
Size And Shape ◽  
Shape Effects ◽  
Nematic Phases

A theory of orientational ordering in uniaxial liquid crystals composed of molecules with alkyl chains

1982 ◽  
Vol 381 (1780) ◽  
pp. 117-138 ◽  
Keyword(s):  
Liquid Crystals ◽  
Orientational Order ◽  
Difficult Problem ◽  
Alkyl Chains ◽  
Cylindrically Symmetric ◽  
Good Accord ◽  
Thermotropic Liquid Crystals ◽  
Methylene Groups ◽  
Nematic Phases ◽  
Conformational Distribution

The constituent molecules of thermotropic liquid crystals invariably contain an aromatic core to which is attached one and often two n -alkyl chains. Nuclear magnetic resonance investigations have revealed that the chain does not exist entirely in an all- trans configuration and that the orientational order of the methylene groups varies markedly along the chain. In this paper we develop a theory to explain these variations for a uniaxial phase at a given temperature and pressure. Our theory contains two distinct parts: one is a model for the conformational distribution of the alkyl chains while the other is for the potential of mean torque experienced by a conformer and which is responsible for its alignment with respect to the director. We use the rotameric state model developed by Flory to describe the conformations adopted by the alkyl chain. The potential of mean torque presents a more difficult problem and we assume that it may be represented by a sum of contributions from each rigid group in the molecule. The order parameters for the methylene and methyl groups in the alkyl chains of the 4- n -pentyl and 4- n -octyl-4'-cyanobiphenyls predicted by the theory are found to be in good accord with those obtained experimentally. We have also used the theory to predict the conformational distributions for both the isotropic and nematic phases of these mesogens; the calculated distributions are contrasted with those assumed by other models. In addition we have obtained the ordering matrices for the various conformers adopted by the two 4- n -alkyl-4'-cyanobiphenyls. The results of these calculations do not support the notion that the orientational order of such molecules can be described by a single, cylindrically symmetric ordering matrix.

RECENT DEVELOPMENTS IN BIAXIAL LIQUID CRYSTALS: AN NMR PERSPECTIVE

2010 ◽  
Vol 24 (24) ◽  
pp. 4641-4682 ◽  
Author(s):  
RONALD Y. DONG
Keyword(s):  
Liquid Crystals ◽  
Nematic Phase ◽  
Orientational Order ◽  
Order Parameters ◽  
Smectic C ◽  
Recent Developments ◽  
Nmr Techniques ◽  
Biaxial Liquid Crystals ◽  
Nematic Phases ◽  
Biaxial Nematic

A survey of recent studies of biaxial liquid crystals (LCs), whose nematic and/or smectic-A phases do not possess optical uniaxiality (viz., more than one optical axis exists), is given in this review. In particular, we emphasize on how Nuclear Magnetic Resonance (NMR) spectroscopy can help to advance the understanding of phase biaxiality in general, and to examine recent debates on the existence of biaxial nematic phase reported in low molecular mass bent-core or V-shaped mesogens. A general discussion of orientational order parameters is detailed, particularly in smectic-C (SmC) and biaxial nematic phases. How these orientational order parameters can be determined by various techniques such as NMR, IR absorbance and Raman scattering studies, will be mentioned. Recent X-ray observations of SmC clusters in the nematic phase of V-shaped mesogens are highlighted and contrasted with probable theory. Moreover, deuterium and carbon-13 NMR techniques are briefly reviewed, and their possible utilization to identify phase biaxiality in these biaxial LC systems is explored.

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