Temperature Variation Of Optical Anisotropy Research Articles

Studies on temperature-dependent optical and electro-optical molecular characterization of terephthal-bis 4, n-decylaniline and cholesteryl oleate

ABSTRACTA binary system of terephthal-bis 4, n-decylaniline (TBDA) and cholesteryl oleate (CO) exhibits a twisted grain boundary (TGB) and induced smectic phases at different concentrations and at different temperatures. Mixtures with higher concentrations of TBDA exhibit I-N*-TGB-SmC-SmA-SmB phases sequentially when the specimen is cooled from its isotropic melt. The temperature variation of optical anisotropy has been discussed. Electro-optical and X-ray studies have also been discussed.

Nano Molecular Self Assembly in the Formation of Induced Mesomorphism in Mixture of ChCl, DTAC, and EG

ABSTRACTThe multi-component system of cholesteryl chloride (ChCl), dodecyl trimethylammonium chloride (DTAC), and ethylene glycol (EG) exhibits very interesting liquid crystalline mesophases like cholesteric and SmA, SmC, and SmB phases sequentially when the specimen is cooled from its isotropic phase. These phases have been characterized by employing optical and X-ray studies. Pitch of the cholesteric phase has been calculated and discussed. Variation of pitch from the cholesteric phase to smectic phase is smooth and continuous. The temperature variation of optical anisotropy and electrical-conductivity has also been discussed. It has been found that wherever there is a phase transition, the value of electrical susceptibility changes appreciably.

Phase transition and thermal stability of reentrant smectic phase in mixture of liquid crystalline materials

ABSTRACTIn the present work, our investigation is to study the optical and thermal properties of the binary mixture of cholesteric and nematic compounds namely, decyloxy benzoic acid (DBA), and cholesteryl chloride (ChCl), which exhibits different liquid crystalline phases with reentrant smectic-A phase. The reentrant smectic-A phase has been observed at different concentrations and at different temperatures. The existence of reentrant smectic-A phase has been observed by optical microscopic studies. The temperature variation of optical anisotropy, X-ray and helical pitch of the cholesteric (N*) phase has also been discussed.

Studies on Optical Characterization and Nano-Aggregation of Molecules in Ternary Mixture of Liquid Crystalline Materials

Two or more multicomponents system of cholesteryl ethyl corbonate, didodecyl dimethyl ammonium bromide, and ethylene glycol exhibits liquid crystalline phase of cholesteric and induced smectic phases, such as SmA, SmC, SmC*, and SmE, sequentially when the specimen is cooled from isotropic liquid phase. These phases have been characterized by using X-ray and optical texture studies. The temperature variation of optical anisotropy and electrical conductivity has also been discussed.

Phase Diagram Involving Induced Smectic Phases in Binary Mixture of Two Liquid Crystals

The binary mixture of cholesteryl oleate (CO) and 4′-n-octyl-4-cyanobiphenyl (8CB) exhibits interesting liquid crystalline mesophase cholesteric and induced smectic phases, such as SmA, SmC, SmB, and SmE, sequentially when the specimen is cooled from its isotropic liquid phase. These phases have been characterized by using differential scanning calorimetric and optical texture studies. The temperature variation of optical anisotropy and electrical conductivity has also been discussed.

Study on Optical Characterization of Binary Mixture of Two Thermotropic Liquid Crystals

In the present work, our investigation is to study the optical and thermal properties of the binary mixture of cholesteric and nematic compounds, namely, cholesteryl oleate (CO) and p-Methoxybenzylidene-p-Ethylaniline (MBEA), which exhibits a very interesting liquid crystalline cholesteric and induced smectic phases like SmA, SmC*, SmC, and SmE phases sequentially when the specimen cooled from isotropic phase. The temperature variation of optical anisotropy is also discussed. X-ray studies have been carried out to understand the intermolecular interactions in the mixture. With the help of phase diagram, the phase behavior has also been discussed.

Induced Polymorphism of Smectic Phases in Binary Mixture of Non-Mesogenic Compounds

We report the results of our studies on the optical and thermal properties of the mixture of sodium dodecyl sulfate (SDS) and orthophosphoric acid (H3PO4), which exhibits very interesting induced polymorphic smectic phases such as smectic-A, smectic-D, smectic-B, and smectic-E phases, sequentially when the specimen is cooled from its isotropic liquid phase. Different liquid crystalline phases observed in the mixture were studied using differential scanning calorimetry (DSC), X-ray, and optical microscopic techniques. The temperature variation of optical anisotropy has also been discussed. Helfrich potential and elastic moduli have been estimated in the smectic phase using Helfrich model.

Chromonic liquid crystalline phase transition involving a biphasic region of nematic and hexagonal phases

We report the results of our studies on the optical and thermal properties of binary mixture of two compounds viz. abietic acid and poly ethylene glycol (PEG). The mixture shows a very interesting co-existent biphasic region of lyotropic nematic (N + I) and intermediate hexagonal (M + I) phases, sequentially when the specimen is cooled from its isotropic phase at different concentrations of abietic acid in PEG. The aggregated molecular size has been confirmed by X-ray studies. The temperature variation of optical anisotropy, electrical conductivity, ultrasonic velocity, and molar and adiabatic compressibility has also been discussed.

Induced Thermotropic Smectic Phases in Binary/Ternary Mixture of Nonmesogenic Compounds

We report the results of our studies on the optical and thermal properties of the mixture of Sodium Lauryl Sulfate (SLS) and Dodecyl trymethyl ammonium bromide + Ethylene glycol (DTAB + EG) exhibits very interesting induced thermotropic smectic phases such as smectic-A, smectic-D, smectic-B, and smectic-E phases, sequentially when the specimen is cooled from its isotropic liquid phase. Different liquid crystalline phases observed in the mixture were studied using DSC, X-ray, and Optical microscopic techniques. The temperature variation of optical anisotropy has also been discussed. Helfrich potential and elastic moduli have been estimated in the smectic phase using Helfrich model.

Thermal Characterization of Induced Mesomorphism in Binary Mixture of Cholesteryl and Poly Ethylene Glycol

We report the results of our studies on optical and thermal properties of two compounds viz., cholesteryl linolenate and poly ethylene glycol exhibits very interesting liquid crystalline-induced lamellar smectic phases at large range of concentrations and temperature. The mixture with lower and higher concentrations of poly ethylene glycol (PEG) exhibits an Iso-N*-SmA-SmE-Cry, sequentially when the specimen is cooled from its isotropic phase. But concentrations from 20% to 40% of the mixture exhibit a SmC* phase. Different phases were observed in the mixture and are identified using X-ray and microscopic techniques. The temperature variation of optical anisotropy and helical pitch measurements are also discussed.

Twisted Grain Boundary Phase in Binary Mixture of Liquid Crystals

In the present work, our investigation is to study the optical and thermal properties of the binary mixture of cholesteric and nematic compounds, namely, cholesteryl chloride and 4,4′-hexyloxy azoxy benzene, which exhibits a very interesting liquid crystalline twisted grain boundary (TGB) phase and induced smectic phases like SmA, SmC*, SmE, and SmB phases. The chiral liquid crystalline TGB phases have been observed at different concentrations and at different temperatures. The mixture with concentration from 26% to 37% of shows I-Ch-TGB-SmA-SmC*-SmE-SmB phases sequentially when the specimen cooled from isotropic phase. The existence of TGB phase is confirmed by DSC and optical microscopic studies. The temperature variation of optical anisotropy is also discussed. X-ray studies have been carried out to understand the intermolecular interactions in the mixture. With the help of phase diagram, the phase behavior has also been discussed.

Optical and Thermal Characterization of Binary Mixtures of Liquid Crystals

We report the results of our studies on the optical and thermal properties of the mixture of cholesteryl nanonate, cetyl-dimethyl-ethylammonium bromide, and ethylene glycol, which exhibits very interesting liquid crystalline mesophases like cholesteric (N*) and induced smectic phases, such as SmA, SmC*, SmE, and SmB, sequentially when the specimen is cooled from its isotropic liquid phase. These phases have been characterized by using differential scanning calorimetric, X-ray diffraction, and optical texture studies. The pitch of the cholesteric phase is discussed. The temperature variation of optical anisotropy, electrical conductivity, ultrasonic velocity, molar, and adiabatic compressibility has also been discussed.

Induced Reentrant Smectic-A Phase in Binary Mixtures of Liquid Crystals

We report the results of our studies on the optical and thermal properties of the mixture of cholesteryl chloride (ChCl) and sodium dodecyl sulphate/water (SDS/water), which exhibits very interesting liquid crystalline mesophases, such as cholesteric (N∗) phase and induced reentrant smectic-A phase, sequentially when the specimen is cooled from its isotropic liquid phase. Different liquid crystalline phases observed in the mixture were studied using DSC, X-ray, and optical microscopic techniques. The pitch of the cholesteric phase and the temperature variation of optical anisotropy have also been discussed.

Thermotropic Liquid Crystalline Phases in Binary Mixture of Nonmesogenic Compounds

The binary mixture of two nonmesogenic compounds viz., Tetradecyl Trimethyl Ammonium Bromide (TTAB) and Orthophosphoric acid (H3PO4) exhibits very interesting liquid crystalline smectic phases at large range of concentrations and temperature. The mixture with lower and higher concentrations of TTAB exhibits Sm A, Sm D, Sm B, and Sm E phases, sequentially when the specimen is cooled from its isotropic phase. Different liquid crystalline phases observed in the mixture were studied using DSC, X-ray, and Optical microscopic techniques. The temperature variation of optical anisotropy has also been discussed. Helfrich potential and elastic moduli have been estimated in the smectic phase using Helfrich model.

Mesomorphic Phases in the Mixtures of the Two Non-Mesogenic Compounds

We report here on the optical and thermal properties of liquid crystalline phases observed in the mixtures of Cetyl pyridinium chloride (CpCl) and Ethylene glycol (EG) at lower concentration of CpCl. The concentration between 10 to 40% of CpCl exhibits I- Sm A - Sm B - Sm E - Cr sequentially, when the specimen is cooled from isotropic phase. The spectroscopic studies like IR and 1 NMR have been carriedout to understand the chemical structure in these mixtures. The phases are identified by the optical, X-ray and DSC studies. Temperature variation of optical anisotropy in these mixtures is also discussed. Helfrich potential and Elastic modulus are estimated in the lamellar Phase using Helfrich model.

Theory of nematic comb-like polymers

Comb polymers with semi-flexible main chains and rod-like nematogenic side chains form interesting nematic phases, largely as a consequence of competition between polymer entropy and rod order. The authors model this competition taking main chains of various stiffness and side groups of various length. Depending on volume fractions, temperature, nematic coupling and stiffness they get one of three nematic phases which they call NI, NII or NIII. They find that at least one component, main or side chain, must be ordered toward a direction, i.e. have a positive order parameter, and the order parameter can be positive or negative. They identify the molecular trends leading to each possibility. The theory, in addition to complex phase diagrams, also predicts unusual properties such as anomalous temperature variation of optical anisotropy and molecular conformational changes. The latter, amenable to small angle neutron scattering, shows a prolate (rod-like) form for the main chain dimension in the NII and NIII phases where the main chain order parameter is positive. The oblate (disk-like) form, the NI phase, is examined in some detail.