EFFECT OF THICKNESS OF LIQUID CRYSTALLINE LAYER ON THE THERMOTROPIC AND THERMODYNAMICAL PROPERTIES OF NEMATIC-ISOTROPIC LIQUID AND ISTROPIC LIQUID-NEMATIC PHASE TRANSITIONS

In this work, effect of thickness of the liquid crystalline layer on the morphologic, thermotropic and thermodynamical properties of the nematic–isotropic liquid and isotropic liquid–nematic phase transitions in Shiff based liquid crystals has been investigated. The shift of temperatures of the nematic–isotropic liquid and isotropic liquid–nematic phase transitions to the lower temperatures and the widening of linear and temperature widths of the heterophase regions of these phase transitions by the increase in the thickness of liquid crystalline layer have been found. The effect of thickness of liquid crystalline layer on morphologic, thermotropic and thermodynamical properties of liquid crystals under investigations is connected with change of interaction energy between liquid crystalline molecules and reference surfaces.

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4-(OCTYLOXY)-N-(4-HEXYLPHENYL)-2-HYDROXYBENZALIMINE THERMOTROPIC COMPOUND: MORPHOLOGIC, MESOMORPHIC, THERMOTROPIC, THERMOOPTICAL AND THERMODYNAMICAL PROPERTIES

International Journal of Modern Physics B ◽

10.1142/s0217979208038582 ◽

2008 ◽

Vol 22 (03) ◽

pp. 281-291 ◽

Cited By ~ 3

Author(s):

ARIF NESRULLAJEV ◽

BELKIZ BILGIN ERAN ◽

ÇIDEM YÖRÜR

Keyword(s):

Phase Transitions ◽

Liquid Crystalline ◽

Crystalline Compound ◽

Reverse Phase ◽

Isotropic Liquid ◽

Thermodynamical Properties ◽

Smectic C ◽

Nematic Mesophase ◽

Liquid Crystalline Compound

In this work, the mesomorphic, morphologic, thermotropic, thermooptical, and thermodynamical properties of 4-(octyloxy)-N-(4-hexylphenyl)-2-hydroxybenzalimine thermotropic liquid crystalline compound, which was synthesized by our group, have been studied in detail. This compound displays smectic C and nematic mesophases. These mesophases are enantiotropic and exhibit specific confocal and schlieren textures, respectively. Thermotropic, thermooptical, and thermodynamical properties of the compound at direct and reverse phase transitions between smectic C and nematic mesophases and also between nematic mesophase and isotropic liquid have been investigated. The peculiarities of the bistable heterophase regions of these phase transitions have been studied.

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Order Parameters, Orientational Distribution Functions and Heliconical Tilt Angles of Oligomeric Liquid Crystals

10.26434/chemrxiv.7679864 ◽

2019 ◽

Author(s):

Richard Mandle ◽

John W. Goodby

Keyword(s):

Phase Transition ◽

Liquid Crystals ◽

Tilt Angle ◽

Order Parameter ◽

Nematic Phase ◽

Liquid Crystalline ◽

Thermal Evolution ◽

Order Parameters ◽

Distribution Functions ◽

Orientational Distribution

We compare the order parameters, orientational distribution functions (ODF) and heliconical tilt angles of the TB phase exhibited by a liquid-crystalline dimer (CB7CB) to a tetramer (O47) and hexamer (O67) by SAXS/WAXS. Following the N-TB phase transition we find that all order parameters decrease, and while 〈P2 〉 remains positive 〈P4 〉 becomes negative. For all three materials the order parameter 〈P6 〉 is near zero in both phases. The ODF is sugarloaf-like in the nematic phase and volcano-like in the TB phase, allowing us to estimate the heliconical tilt angle of each material and its thermal evolution. The heliconical tilt angle appears to be largely independent of the material studied despite the differing number of mesogenic units.

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Chromonic liquid crystalline nematic phase exhibited in binary mixture of two liquid crystals

10.1063/1.4917616 ◽

2015 ◽

Author(s):

T. N. Govindaiah ◽

H. R. Sreepad ◽

K. N. Sridhar ◽

G. R. Sridhara ◽

N. Nagaraja

Keyword(s):

Liquid Crystals ◽

Binary Mixture ◽

Nematic Phase ◽

Liquid Crystalline

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Structural studies on different types of ferroelectric liquid crystalline substances

Journal of Research in Physics ◽

10.2478/v10242-012-0001-3 ◽

2011 ◽

Vol 35 (1) ◽

pp. 3-13 ◽

Cited By ~ 5

Author(s):

D. Obadović ◽

M. Stojanović ◽

A. Bubnov ◽

N. Éber ◽

M. Cvetinov ◽

...

Keyword(s):

Phase Transitions ◽

Liquid Crystals ◽

Liquid Crystalline ◽

Molecular Conformation ◽

Large Angle ◽

Structural Studies ◽

Layer Spacing ◽

Different Types ◽

Intermolecular Distances ◽

Chiral Liquid Crystals

Structural studies on different types of ferroelectric liquid crystalline substances Structural studies of ferroelectric liquid crystalline substances of different molecular structure have been reviewed. The discussion of the results deals mainly with the structure of chiral liquid crystals forming the smectic mesophase with ferroelectric order, as the research on ferroelectric liquid crystals, due to their high potential for application in electro-optics and photonics, has recently become one of the most attractive fields. Based on data of polarizing optical microscopy and X-ray diffraction obtained for unoriented samples we have identified the type of the mesophases, the temperature of the phase transitions and outlined the phase diagrams. An analysis of the relation between the molecular conformation and different types of phase transitions has been performed. The layer spacing and the average intermolecular distances have been determined for all studied phases from the positions of the small and the large angle diffraction peaks, respectively.

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‘Quasi-Tricritical’ and Glassy Dielectric Properties of a Nematic Liquid Crystalline Material

Crystals ◽

10.3390/cryst10040297 ◽

2020 ◽

Vol 10 (4) ◽

pp. 297 ◽

Cited By ~ 1

Author(s):

Aleksandra Drozd-Rzoska

Keyword(s):

Relaxation Time ◽

Nematic Phase ◽

Liquid Crystalline ◽

Strong Electric Field ◽

Low Frequency ◽

Ionic Species ◽

Crystalline Material ◽

Isotropic Liquid ◽

The Impact ◽

Liquid Crystalline Material

Results of dielectric studies in the nematic and isotropic liquid phases of pentylcyanobiphenyl (5CB), a model rod-like liquid crystalline material, are shown. They are based on the discussion of the evolution of dielectric constant ( ε ), its changes under the strong electric field (nonlinear dielectric effect, NDE), and finally, the primary relaxation time. It is shown that changes in ε T and NDE are entirely dominated by the impact of pretransitional fluctuations (pre-nematic and pre-isotropic, respectively) which are associated with the weakly discontinuous character of the isotropic–nematic phase transition. This influence also extends for the low-frequency, ionic species dominated, region. Notable, that the derivative-based and distortions sensitive analysis revealed the tricritical nature of the I-N transition. Although the glass transition in 5CB occurs in the deeply supercooled state at T g ≈ − 68 ° C , the dynamics (changes of the primary relaxation time) follow a previtreous pattern both in the isotropic and in the nematic phase. Finally, the discussion of the ’molecular’ vs. ‘quasi-critical’ characterizations of the isotropic and nematic phases is presented. It shows the evident prevalence of the ‘quasi-critical-picture’, which offers the consistent temperature parameterization in the total tested temperature range.

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