S. Chandrasekhar

Bio: S. Chandrasekhar is an academic researcher from Raman Research Institute. The author has contributed to research in topics: Liquid crystal & Biaxial nematic. The author has an hindex of 31, co-authored 124 publications receiving 3368 citations. Previous affiliations of S. Chandrasekhar include Royal Institution & University of Mysore.

A New Multicritical Point in a Single Component Liquid Crystal: High Pressure Study of DOBBCA

Abstract: We report here the results of our high pressure optical and DTA studies on the compound 4(4-n-decyloxybenzoyloxy)-benzylidene-4'-cyanoaniline. The P-T diagram shows a new kind of multicritical poin...

Near Neighbour Correlations and the Dielectric Properties of Liquid Crystals

Abstract: It is demonstrated experimentally that there can be a reversal of the sign of the dielectric anisotropy (Δϵ) with decreasing temperature in a nematic. The results are explainable in terms of the Maier-Meier mean field theory and indicate that the occurrence of the smectic phase and the consequent dipole correlations within the smectic layers is not a necessary condition for the sign reversal of Δϵ.

The temperature variation of the rotatory power of quartz from 30° to 410° C.

Abstract: The temperature variation of the rotatory power of quartz has been measured from 30° to 410° C. for a range of wavelengths extending from 6000 A to 2500 A. It is found that the temperature coefficient\(\left( {\frac{1}{{\rho _0 }} \frac{{\Delta \rho }}{{\Delta t}}} \right)\) exhibits an increase in the ultraviolet. The rotatory dispersion of quartz is accurately expressible from the visible to the extreme ultraviolet by a formula of the form\(\rho = {{av^2 } \mathord{\left/ {\vphantom {{av^2 } {\left( {v_0 ^2 - v^2 } \right)^2 }}} \right. \kern- ulldelimiterspace} {\left( {v_0 ^2 - v^2 } \right)^2 }}\), where\(v = \frac{1}{\lambda }\) Taking ‘a’ to be invariable with temperature (for which reasons have been put forward) but v0 to vary with it, the thermal variation of the rotatory power has been calculated over the whole range of wavelengths for the different temperatures. The theoretical calculation agrees very well with the observational data, the rate of shift of v0 being found to be roughly the same as that estimated from the thermal variation of the refraction. It is shown that theoretically we should expect the temperature coefficient to increase with decrease of wavelength, a fact which is confirmed by experiment.

The Topology of the P-T Diagram of DOBBCA in the Vicinity of the Reentrant Nematic—Smectic C—Smectic A Multicritical Point

Abstract: The P-T diagram of 4(4-n-decyloxybenzoyloxy)-benzylidene-4′-cyanoanihe shows a new kind of multicriticd point, viz., a reentrant nematic-smectic C-smectic A point, at 0.55 ± 0.01 kbar and 86.8 ± 0....

Relationship between elasticity and orientational order in nematic liquid crystals

Abstract: The constants of the potential energy function deduced from the statistical theory of orientational order in nematic liquid crystals are given for a few compounds and their significance in relation to the molecular structure is discussed. The dependence of the free energy of elastic deformation and the intensity of light scattering on the orientational order parameters is then investigated theoretically. Calculations show that the elastic moduli should be greater and the scattering cross-section less in p-azoxyphenetole than in p-azoxyanisole. The results are in quantitative agreement with the available experimental data. The theory is also able to account for the observed fact that though the order parameters and the elastic moduli decrease rapidly with rise of temperature, the light scattering remains practically constant throughout the nematic range.

Handbook of Optical Materials

Abstract: CRYSTALLINE MATERIALS Introduction Physical Properties Optical Properties Mechanical Properties Thermal Properties Magnetooptic Properties Electrooptic Properties Elastooptic Properties Nonlinear Optical Properties GLASSES Introduction Commercial Optical Glasses Specialty Optical Glasses Fused Silica Fluoride Glasses Chalcogenide Glasses Magnetooptic Properties Electrooptic Properties Elastooptic Properties Nonlinear Optical Properties Special Glasses POLYMERIC MATERIALS Optical Plastics Index of Refraction Nonlinear Optical Properties Thermal Properties Engineering Data METALS Physical Properties of Selected Metals Optical Properties Mechanical Properties Thermal Properties Mirror Substrate Materials LIQUIDS Introduction Water Physical Properties of Selected Liquids Index of Refraction Nonlinear Optical Properties Magnetooptic Properties Commercial Optical Liquids GASES Introduction Physical Properties of Selected Gases Index of Refraction Nonlinear Optical Properties Magnetooptic Properties Atomic Resonance Filters APPENDICES Safe Handling of Optical Materials Abbreviations, Acronyms, and Mineralogical or Common Names for Optical Materials Abbreviations for Methods of Preparing Optical Materials and Thin Films Fundamental Physical Constants Units and Conversion Factors

Dendron-Mediated Self-Assembly, Disassembly, and Self-Organization of Complex Systems

Abstract: Dendron-mediated self-assembly, disassembly, and self-organization of complex systems have been investigated. The most ideal building blocks would need to display shape persistence in solution and in the solid state, since only this feature provides access to the use of complementary methods of structural analysis. Most supramolecular dendrimers are chiral even when they are constructed from nonchiral building blocks and are equipped with mechanisms that amplify chirality. This poses additional challenges associated with the understanding of the structural origin of chirality in different supramolecular structures through combinations of structural analysis methods. While many supramolecular structures assembled from dendrimers and dendrons resemble some of the related morphologies generated from block-copolymers, they are much more complex and are not determined by the volume ratio between the dissimilar parts of the molecule.

Discotic Liquid Crystals: From Tailor-Made Synthesis to Plastic Electronics

Abstract: Most associate liquid crystals with their everyday use in laptop computers, mobile phones, digital cameras, and other electronic devices. However, in contrast to their rodlike (calamitic) counterparts, first described in 1907 by Vorlander, disklike (discotic, columnar) liquid crystals, which were discovered in 1977 by Chandrasekhar et al., offer further applications as a result of their orientation in the columnar mesophase, making them ideal candidates for molecular wires in various optical and electronic devices such as photocopiers, laser printers, photovoltaic cells, light-emitting diodes, field-effect transistors, and holographic data storage. Beginning with an overview of the various mesophases and characterization methods, this Review will focus on the major classes of columnar mesogens rather than presenting a library of columnar liquid crystals. Emphasis will be given to efficient synthetic procedures, and relevant mesomorphic and physical properties. Finally, some applications and perspectives in materials science and molecular electronics will be discussed.