scholarly journals Determination of the temperature dependence of the helical pitch in 1.m.7(HH) liquid crystalline compounds

2018 ◽  
Vol 67 (2) ◽  
pp. 49-61
Author(s):  
Paulina Zieja ◽  
Marzena Tykarska ◽  
Katarzyna Strójwąs
Keyword(s):  
Liquid Crystals ◽  
Temperature Dependence ◽  
Liquid Crystalline ◽  
Helical Pitch ◽  
Antiferroelectric Phase ◽  
Left Handed ◽  
Helical Twist ◽  
Phase Transition Temperatures ◽  
The Right

Homologous series 1.m.7(HH) of liquid crystalline compounds, varying in the chiral chain length m (m=4-9), were studied. These compounds are characterized by a long helical pitch in an antiferroelectric phase, which is higher than the measuring range of the available instruments. The temperature dependence of the helical pitch of these compounds was determined by the extrapolation of the results obtained for the mixtures of 1.m.7(HH) compounds with 1.4.7(HF) compound of a known helical pitch value. The helical pitch measurements were made by spectrophotometry and phase transition temperatures were measured by polarizing thermomicroscopy. Extrapolation of the results let established that the investigated liquid crystals are characterized by the helical pitch increasing and then decreasing upon heating, which is accompanied by the helical twist sense inversion from the right-handed structure to the left-handed one. Keywords: liquid crystals, antiferroelectric phase, helical pitch, miscibility study

scholarly journals Regiospecific synthesis of tetrasubstituted phthalocyanines and their liquid crystalline order

2015 ◽  
Vol 44 (12) ◽  
pp. 5569-5576 ◽  
Author(s):  
Petru Apostol ◽  
Ahmed Bentaleb ◽  
Mbolotiana Rajaoarivelo ◽  
Rodolphe Clérac ◽  
Harald Bock
Keyword(s):  
Liquid Crystals ◽  
Liquid Crystalline ◽  
Crystalline Order ◽  
Size And Shape ◽  
The Right

The right place, size and shape of substituent make the cyclotetramerisation of alkoxy-phthalonitriles regiospecific and yield columnar liquid crystals with attainable clearing points.

scholarly journals ARS leptogenesis

2018 ◽  
Vol 33 (05n06) ◽  
pp. 1842002 ◽  
Author(s):  
M. Drewes ◽  
B. Garbrecht ◽  
P. Hernández ◽  
M. Kekic ◽  
J. Lopez-Pavon ◽  
...  
Keyword(s):  
Bayesian Analysis ◽  
Parameter Space ◽  
Kinetic Equations ◽  
Lepton Number ◽  
Current Status ◽  
Mass Eigenstates ◽  
Left Handed ◽  
Theoretical Approaches ◽  
The Right

We review the current status of the leptogenesis scenario originally proposed by Akhmedov, Rubakov and Smirnov (ARS). It takes place in the parametric regime where the right-handed neutrinos are at the electroweak scale or below and the CP-violating effects are induced by the coherent superposition of different right-handed mass eigenstates. Two main theoretical approaches to derive quantum kinetic equations, the Hamiltonian time evolution as well as the Closed-Time-Path technique are presented, and we discuss their relations. For scenarios with two right-handed neutrinos, we chart the viable parameter space. Both, a Bayesian analysis, that determines the most likely configurations for viable leptogenesis given different variants of flat priors, and a determination of the maximally allowed mixing between the light, mostly left-handed, and heavy, mostly right-handed, neutrino states are discussed. Rephasing invariants are shown to be a useful tool to classify and to understand various distinct contributions to ARS leptogenesis that can dominate in different parametric regimes. While these analyses are carried out for the parametric regime where initial asymmetries are generated predominantly from lepton-number conserving, but flavor violating effects, we also review the contributions from lepton-number violating operators and identify the regions of parameter space where these are relevant.

Synthesis of New Chiral Disubstituted Binaphthol Derivatives and their use as the Chiral Dopants

1996 ◽  
Vol 425 ◽  
Author(s):  
H.-J. Deussen ◽  
P. V. Shibaev ◽  
R. A. Vinokur ◽  
K. Schaumburg ◽  
T. Bjornholm ◽  
...  
Keyword(s):  
Liquid Crystals ◽  
Temperature Dependence ◽  
Liquid Crystalline ◽  
Molecular Conformation ◽  
Molecular Model ◽  
Nematic Liquid Crystals ◽  
Spatially Extended ◽  
Chiral Dopants ◽  
Helical Twisting Power

AbstractA number of new chiral binaphthol (BN) derivatives with different substituents in the 6,6'-positions in open and bridged forms have been synthesized. Their possible liquid crystalline properties and their helical twisting power (B) of three different nematic liquid crystals (LCs) were investigated. Derivatives with spatially extended substituents in the 6,6'-positions (e.g. styryl or vinil) show unusual high helical twisting power (up to 120 μm–1). A direct correlation between the magnitude of β and the length of the substituents was found.From the different temperature dependence of β of the open and bridged BNs, a molecular model was developed relating the molecular conformation and twisting power

Bestimmung elastischer Konstanten von MBBA und EBBA mit der elektrischen Leitfähigkeitsmethode / Determination of the Elastic Constants of MBBA and EBBA by Electric Conductivity Measurements

1975 ◽  
Vol 30 (4) ◽  
pp. 515-518 ◽  
Author(s):  
M. Greulich ◽  
G. Heppke ◽  
F. Schneider
Keyword(s):  
Magnetic Susceptibility ◽  
Liquid Crystals ◽  
Temperature Dependence ◽  
Electric Conductivity ◽  
Elastic Constants ◽  
Nematic Liquid Crystals ◽  
Elastic Behaviour ◽  
Conductivity Measurements

Abstract Several methods of studying the elastic behaviour of nematic liquid crystals by means of measuring the electric conductivity are discussed. The temperature dependence of the ratio of the splay and bend elastic constants to the anisotropy of the magnetic susceptibility is determined for N-(p-methoxybenzylidene) -p-n-butylaniline (MBBA), N-(p-ethoxybenzylidene) -p-n-butylaniline (EBBA) and mixtures of both.

scholarly journals PHASE TRANSITION STUDIES OF CHOLESTERYL PALMITATE, CHOLESTERYL DECANOATE AND THEIR MIXTURES USING DIELECTRIC, EPR AND DTA TECHNIQUES

2021 ◽  
Vol 9 (11) ◽  
pp. 210-223
Author(s):  
Sanjai Misra ◽  
Keyword(s):  
Phase Transition ◽  
Liquid Crystals ◽  
Order Parameter ◽  
Liquid Crystalline ◽  
Paramagnetic Resonance ◽  
Crystalline Materials ◽  
Phase Transition Temperatures ◽  
Cholesteryl Palmitate ◽  
Liquid Crystalline Materials ◽  
Electron Paramagnetic

The phase transition of two liquid crystalline materials, namely cholesteryl palmitate and cholesteryl decanoate and their mixtures (by weight)are studied using dielectric, Electron paramagnetic resonance (EPR) and differential thermal analysis (DTA) techniques. From the dielectric measurements, the phase transition temperatures were determined from the discontinuities in the curve between dielectric constant and temperatures for all the samples investigated. Further, since mixing of two liquid crystals modifies the transition of phases, the measurements were carried out on the mixtures of the two liquid crystals. Order parameter for each sample was calculated at varying temperatures by measuring the hyperfine splitting of three line EPR spectrums. The discontinuities in the curve between order parameter and the temperature again indicated the phase transition of the liquid crystals and their mixtures. A DTA study on these samples was also carried out in order to probe further their transitional behaviour. The DTA records of both the liquid crystals and their mixtures support the transition behaviour observed from the dielectric and EPR measurements.

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