nan Nagappa

Optical behavior of natural oils and fats of plant origin.

Abstract The paper describes and discusses the results of the observations made on the optical textures exhibited by sixteen naturally occurring oils and fats of plant origin. The textures observed here consist of spherulites, drops, batonnets and maltese crosses which are characteristic of liquid crystals. The refractive indices and the average isotropic polarizabilities of these substances are also discussed. Often it is found that the mesomorphic nature is more pronounced with oils and fats with a high component of saturated triglycerides and with high molecular weights. The paper is illustrated by numerous striking photographs.

Micellar Nematic Phase in a Binary Mixture of Two Nonmesogenic Compounds

We report the results of our studies on the optical and thermal properties of two nonmesogenic compounds, namely, tetradecyl trimethyl ammonium bromide (TTAB) and glacial acetic acid (GAA). The mixture exhibits very interesting schilieren texture of micellar nematic lyophase, smectic A (SmA), and SmG phases for all concentrations of TTAB sequentially when the specimen is cooled from its isotropic phase. The order parameter (S) of the micellar nematic phase is estimated with the help of temperature dependence of optical anisotropy from the measured refractive index and density data. The temperature variation of order parameter of the experimental curve is very well fitted with the Mayer–Saupe theoretical curve. The temperature variation of electrical conductivity is also discussed. The formation of above phases has been confirmed by optical X-ray and differential scanning calorimetry studies.

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.

Mesophase Formation in Binary Mixtures of Berberine and Glacial Acetic Acid

We report the results of our studies on the optical and thermal properties of binary mixture of compounds, viz., Berberine (BBE) and Glacial acetic acid (GAA). The mixture shows very interesting coexistent nematic biphase (N+I) and nematic phase for different concentrations of BBE sequentially when the specimen is cooled from its isotropic phase. The order parameter (S) of the coexistent nematic biphase is estimated with the help of optical anisotropy from the measured refractive index and density data. The temperature variation curve of experimentally found order parameter is well fitted with the Maier–Saupe theoretical curve. The temperature variation of electrical conductivity is also discussed. Formation of above molecular orientations has been confirmed by optical studies.

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 the binary mixture of nematic and cholesteryl compounds

Abstract The binary mixture of cholesteryl nonanoate(CN) and 4,4′-hexyloxy azoxy benzene (HOB) exhibit a very interesting sesophases like blue phase, twisted grain boundary (TGB) phase, induced smectic A, smectic C and smectic B phases at different temperatures when the mixture is cooled from isotropic phase. The existence of TGB phase is confirmed by DSC and optical microscopic studies. The mixtures with concentration 30 to 45% of CN exhibit TGB phase at higher temperature. The optical anisotropy of cholesteric phase is estimated. Numerous interesting optical textures are also illustrated.

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.

Induced Chiral Smectic Phase in Mixtures of Mesogenic and Non-Mesogenic Compounds

The mixture of cholesteryl chloride (CCl), cetyl pyridinium chloride, and ethylene glycol exhibits very interesting liquid crystalline mesophase cholesteric (N*) and induced smectic phases, such as Sm A, Sm C*, and Sm E, sequentially when the specimen is cooled from its isotropic liquid phase. These phases have been characterized by using differential scanning calorimetric (DSC), X-ray diffraction, nuclear magnetic resonance (NMR), infrared (IR), and optical texture studies.

Non Linear Optical Properties of Banana Shaped Liquid Crystals

We report the nonlinear absorption and refraction of banana shaped liquid crystal, namely 1,3-phynelyne bis [N-(2-hydroxy-4-n-decyloxy-benzylidene)-4′-aminobenzoate] using Z-scan technique. The measurements were carried out using a Q-switched, frequency doubled Nd:YAG laser producing 7 nanosecond laser pulses at 532 nm. The Z-scan result shows that the compound exhibits negative non-linearity. The nonlinear refractive index and nonlinear absorption coefficient of this compound were found to be −1.283 × 10−11 esu and 2.232 cm/GW, respectively. The real and imaginary parts of the third-order nonlinear optical susceptibility were of the order of 10−13 esu. The results suggest that these molecules are potential nonlinear optical materials for device applications.

Anisotropic Molecular Orientation of Micellar Nematic Phase in a Binary Mixture of Two Nonmesogenic Compounds

We report the results of our studies on the optical and thermal properties of two nonmesogenic compounds, namely, Cetyl-dimethyl-ethylammonium bromide (CDEAB) and Glacial acetic acid. The mixture exhibits very interesting schilieren texture of micellar nematic phase, SmA, SmC*, and SmE phases, respectively, at different concentrations of CDEAB sequentially when the specimen is cooled from its isotropic phase. The order parameter (S) of the micellar nematic phase is estimated with the help of temperature dependence of optical anisotropy from the measured values refractive index and density data. The temperature variation of order parameter of the experimental curve is very well fitted with the Mayer–Saupe theoretical curve. X-ray studies have been discussed. The formation of above phases has been confirmed by optical and DSC studies.