About Supramolecular Assemblies of π-Conjugated Systems

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

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Handbook of Optical Materials

Big is beautiful--"aromaticity" revisited from the viewpoint of macromolecular and supramolecular benzene chemistry.

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.

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

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.

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

It is shown that the essential features of Helfrich’s permeation model for flow along the helical axis of a cholesteric liquid crystal can be derived approximately on the basis of the Ericksen-Leslie theory

Flow of cholesteric liquid crystals—I: Flow along the helical axis

Some of the more recent advances in the field of liquid crystals are summarized, with emphasis on the experimental developments rather than their theoretical implications. A major part of the discussion is devoted to newly discovered phases and phase transitions, particularly those that are of special interest to condensed matter physicists. Observations are also described of two new phenomena, which, although predicted by the continuum theory, have eluded experimentalists for many years: (a) the appearance of a regular network of singular points at the nematic-isotropic interface and (b) the Lehmann rotation effect in cholesteric liquid crystals under the action of a d.c. electric field.

Recent developments in the physics of liquid crystals

The pressure-temperature diagram of N-(4-n-pentyloxybenzylidene)-4′-n-hexylaniline has been investigated up to 8 kbar. The smectic C-smectic A and smectic A-nematic phase boundaries converge and nearly meet, indicating that a Lifshitz point is likely to occur at a higher pressure.

The Search for a Lifshitz Point in a Single-Component Liquid Crystalline System: A High Pressure Study of 50.6

The refractivity and the dispersion of vitreous silica are shown to be calculable from those of quartz by considering the diminished density. The temperature variation of its refractive indices over the entire range of wavelengths is in quantitative accord with the hypothesis that the characteristic absorption frequencies in the ultra-violet fall with rise of temperature. The rate of change of these frequencies has been traced from −160° to 1000°C. and shows remarkable variations in the vicinity of the temperature at which theα-β transformation in crystalline quartz occurs.

The dispersion and thermo-optic behaviour of vitreous silica

We report high pressure studies on a binary system of 4-(2′-methyl butyl)phenyl 4′-n-octyl biphenyl-4-carboxylate (CE8 from BDH) and 4-n- dodecyloxy biphenyl-4′-(2′-methyl butyl)benzoate (C12). For the concentration range 0.32<X<0.62, where X is the weight fraction of C12, the system shows the following sequence of transitions at room pressure: Isotropic- Cholesteric (Ch)-Twist Grain Boundary (TGB)-Smectic A (A)Smectic C− (C*). For X=0.25, the Ch phase transforms directly to the A phase at 1 bar, but there is an induced TGB phase between the Ch and A phases at elevated pressures. Analysis of the topology of the pressure-temperature diagram in the vicinity of the Ch-TGB-A meeting point indicates that is a critical end point rather than a bicritical point as expected from the mean field theory. At X=0.64 there is a direct TGB-C* transition at 1 bar, but there appears a pressure induced A phase between the TGB and C* phases. The topology of the phase diagram suggests that the TGB-A-C* meeting point ...

S. Chandrasekhar

Papers

Flow of cholesteric liquid crystals—I: Flow along the helical axis

Recent developments in the physics of liquid crystals

The Search for a Lifshitz Point in a Single-Component Liquid Crystalline System: A High Pressure Study of 50.6

The dispersion and thermo-optic behaviour of vitreous silica

Pressure Induced Twist Grain Boundary Phase