Discotic (disc-like) molecules typically comprising a rigid aromatic core and flexible peripheral chains have been attracting growing interest because of their fundamental importance as model systems for the study of charge and energy transport and due to the possibilities of their application in organic electronic devices. This critical review covers various aspects of recent research on discotic liquid crystals, in particular, molecular design concepts, supramolecular structure, processing into ordered thin films and fabrication of electronic devices. The chemical structure of the conjugated core of discotic molecules governs, to a large extent, their intramolecular electronic properties. Variation of the peripheral flexible chains and of the aromatic core is decisive for the tuning of self-assembly in solution and in bulk. Supramolecular organization of discotic molecules can be effectively controlled by the choice of the processing methods. In particular, approaches to obtain suitable macroscopic orientations of columnar superstructures on surfaces, that is, planar uniaxial or homeotropic alignment, are discussed together with appropriate processing techniques. Finally, an overview of charge transport in discotic materials and their application in optoelectronic devices is given (234 references).

Discotic liquid crystals: a new generation of organic semiconductors

Light-driven phenomena both in living systems and nonliving materials have enabled truly fascinating and incredible dynamic architectures with terrific forms and functions. Recently, liquid crystalline materials endowed with photoresponsive capability have emerged as enticing systems. In this Review, we focus on the developments of light-driven liquid crystalline materials containing photochromic components over the past decade. Design and synthesis of photochromic liquid crystals (LCs), photoinduced phase transitions in LC, and photoalignment and photoorientation of LCs have been covered. Photomodulation of pitch, polarization, lattice constant and handedness inversion of chiral LCs is discussed. Light-driven phenomena and properties of liquid crystalline polymers, elastomers, and networks have also been analyzed. The applications of photoinduced phase transitions, photoalignment, photomodulation of chiral LCs, and photomobile polymers have been highlighted wherever appropriate. The combination of photoc...

Light-Driven Liquid Crystalline Materials: From Photo-Induced Phase Transitions and Property Modulations to Applications.

Field-Cycling NMR Relaxometry

Gas-phase spectroscopy lends itself ideally to the study of isolated molecules and provides important data for comparison with theory. In recent years, we have seen enormous progress in the study of biomolecular building blocks in the gas phase. The motivation for such work is threefold: (a) It is important to distinguish between intrinsic molecular properties and properties that result from the biological environment. (b) Gas-phase spectroscopy of clusters provides insights into fundamental interactions and into microsolvation. (c) Gas-phase data support quantum-chemical calculations. This review focuses on the current status of (poly)amino acids and DNA bases. Recent results help elucidate structure and hydrogen-bonded interactions, as well as showcase a successful interplay between theory and experiment.

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Gas-phase spectroscopy of biomolecular building blocks.

Density-functional theory (DFT) and its variations provide a fruitful approach to the computational modeling of the microscopic structures and phase behavior of soft-condensed matter. The methodology takes deep root in quantum mechanics but shares a mathematical similarity with a number of classical approaches in statistical mechanics. This review discusses different strategies commonly used to formulate the free-energy functional of complex fluids for either phenomena-oriented applications or as a generic description of the thermodynamic nonideality owing to various components of intermolecular forces. We emphasize the connections among different schemes of DFT approximations, their underlying assumptions, and inherent limitations. We also address extensions of equilibrium DFT to phenomenological theories for the dynamic properties of complex fluids and for the kinetics of phase transitions. In addition, we highlight the recent literature concerning applications of DFT to diverse static and time-dependent phenomena in complex fluids.

Density-Functional Theory for Complex Fluids

Phase transitions in liquid crystals

Liquid crystals: main types and classification distribution functions and order parameters physical properties of liquid crystals nematic liquid crystals nematic liquid crystals - elastostatics and nematodynamics smectic liquid crystals liquid crystals of disc-like molecules polymer liquid crystals chiral liquid crystals lyotropic liquid crystals defects and textures in liquid crystals.

Liquid crystals : fundamentals

Carbon nanotube dispersion in nematic liquid crystals: An overview

The present study focuses on the ionic behaviour in nanoparticles (NPs) dispersed nematic liquid crystal. Dielectric spectroscopy has been used to investigate the behaviour of ions in suspension of NPs and liquid crystal (LC). Ionic concentration, diffusion coefficient, activation energy and mobility have been calculated from dielectric data. It is found that ion concentration increases initially and then it decreases with increasing concentration of NPs in suspension. The initial increase in ion concentration is attributed to the insertion of more ions due to impurities of TiO2 NPs and various other reasons. Temperature dependence of diffusion constant for different loading of TiO2 NPs is also investigated. The activation energy of NPs dispersed LC is found to be lower than the pristine one and it decreases with increasing concentration of NPs. The decreasing DC conductivity with increasing NPs concentration is attributed to the hindered or restricted motion of ions in the suspension. It is proposed that...

Shri Singh

Papers

Phase transitions in liquid crystals

Liquid crystals : fundamentals

Carbon nanotube dispersion in nematic liquid crystals: An overview

Effect of TiO2 nanoparticles dispersion on ionic behaviour in nematic liquid crystal

Tuning the photoluminescence of ferroelectric liquid crystal by controlling the size of dopant ZnO quantum dots