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.

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

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.

The Dynamic Properites of Confined Antiferroelectric Liquid Crystal Investigated By Photon Correlation Spectroscopy

1999 ◽  
Vol 559 ◽  
Author(s):  
Yu.P. Panarin ◽  
C. Rosenblatr ◽  
F.M. Aliev
Keyword(s):  
Phase Transition ◽  
Porous Media ◽  
Liquid Crystalline ◽  
Photon Correlation Spectroscopy ◽  
Correlation Spectroscopy ◽  
Photon Correlation ◽  
Crystalline Materials ◽  
Liquid Crystalline Phases ◽  
Liquid Crystalline Materials ◽  
Structural Aspects

ABSTRACTDynamic light scattering was used to examine ferrielectric liquid crystalline phases in porous media. Whereas in larger pores (200 Å) ferrielectric phases were observed, they were not found in the smallest pores (200 Å). Additionally, the temperatures of SmC - SmA phase transition were found to be suppressed in the pores relative to bulk, while SmCA - SmCγ phase transition is not affected by the confinement. These observations have been explained by the structural aspects of antiferroelectric liquid crystalline materials in a confined geometry and show the importance of long range electrostatic interaction for existence of ferrielectric phases.

scholarly journals Light Propagation in Confined Nematic Liquid Crystals and Device Applications

2021 ◽  
Vol 11 (18) ◽  
pp. 8713
Author(s):  
Antonio d’Alessandro ◽  
Rita Asquini
Keyword(s):  
Liquid Crystals ◽  
Optical Switching ◽  
Liquid Crystalline ◽  
Light Propagation ◽  
Soda Lime ◽  
Significant Feature ◽  
Molecular Reorientation ◽  
Crystalline Materials ◽  
Integrated Optic Devices ◽  
Liquid Crystalline Materials

Liquid crystals are interesting linear and nonlinear optical materials used to make a wide variety of devices beyond flat panel displays. Liquid crystalline materials can be used either as core or as cladding of switchable/reconfigurable waveguides with either an electrical or an optical control or both. In this paper, materials and main device structures of liquid crystals confined in different waveguide geometries are presented using different substrate materials, such as silicon, soda lime or borosilicate glass and polydimethylsiloxane. Modelling of the behaviour of liquid crystal nanometric molecular reorientation and related refractive index distribution under both low-frequency electric and intense optical fields is reported considering optical anisotropy of liquid crystals. A few examples of integrated optic devices based on waveguides using liquid crystalline materials as core for optical switching and filtering are reviewed. Reported results indicate that low-power control signals represent a significant feature of photonic devices based on light propagation in liquid crystals, with performance, which are competitive with analogous integrated optic devices based on other materials for optical communications and optical sensing systems.

scholarly journals Artificial colloidal liquid metacrystals by shearing microlithography

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Yanqiu Jiang ◽  
Fan Guo ◽  
Zhen Xu ◽  
Weiwei Gao ◽  
Chao Gao
Keyword(s):  
Liquid Crystals ◽  
Liquid Crystalline ◽  
Molecular Size ◽  
Digital Design ◽  
Lyotropic Liquid Crystals ◽  
Colloidal Systems ◽  
Extended Form ◽  
Crystalline Materials ◽  
Liquid Crystalline Materials ◽  
External Stimuli

Abstract Meta-periodicity beyond intrinsic atomic and molecular order, such as metacrystalline and quasicrystalline lattices, exists in solids, but is usually elusive in lyotropic liquid crystals for its energetic instability. The stable meta-periodicity in lyotropic liquid crystals in the absence of external stimuli remains unexplored, and how to achieve it keeps a great challenge. Here we create lyotropic liquid crystals with stable meta-periodicity in a free state, coined as liquid metacrystals, in colloidal systems by an invented shearing microlithography. The meta-periodicity is dynamically stabilized by the giant molecular size and strong excluded volume repulsion. Liquid metacrystals are designed to completely cover a library of symmetries, including five Bravais and six quasicrystalline lattices. Liquid metacrystal promises an extended form of liquid crystals with rich meta-periodicity and the shearing microlithography emerges as a facile technology to fabricate liquid meta-structures and metamaterials, enabling the digital design of structures and functionalities of liquid crystalline materials.

scholarly journals Inexpensive, operationally simple flow reactor for rapid, chromatography free synthesis of siloxane based liquid crystals

2018 ◽  
Vol 3 (4) ◽  
pp. 515-519 ◽  
Author(s):  
Richard J. Mandle ◽  
John W. Goodby
Keyword(s):  
Liquid Crystals ◽  
Liquid Crystalline ◽  
Flow Reactor ◽  
Crystalline Materials ◽  
Terminal Alkenes ◽  
Liquid Crystalline Materials ◽  
Simple Flow

We report on the hydrosilylation of terminal alkenes in flow using a “Karstedt-like” platinum-on-silica catalyst to afford liquid-crystalline materials.

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