About Supramolecular Assemblies of π-Conjugated Systems

Charge-Transfer and Energy-Transfer Processes in π-Conjugated Oligomers and Polymers: A Molecular Picture

Graphenes as potential material for electronics.

羟氨苄青霉素引起大疱性类天疱疮样疹

: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

The hierarchical self-assembly of disc-shaped molecules leads to the formation of discotic liquid crystals. These materials are of fundamental importance not only as models for the study of energy and charge migration in self-organized systems but also as functional materials for device applications such as, one-dimensional conductors, photoconductors, light emitting diodes, photovoltaic solar cells, field-effect transistors and gas sensors. The negative birefringence films formed by polymerized nematic discotic liquid crystals have been commercialized as compensation foils to enlarge the viewing angle of commonly used twisted nematic liquid crystal displays. To date the number of discotic liquid crystals derived from more than 50 different cores comes to about 3000. This critical review describes, after an in-depth introduction, recent advances in basic design principles and synthetic approaches towards the preparation of most frequently encountered discotic liquid crystals.

Self-organization of disc-like molecules: chemical aspects

Liquid crystals are finding increasing applications in a wide variety of fields including liquid-crystal display technology, materials science, bioscience, etc., apart from acting as prototype self-organizable supramolecular soft materials and tunable solvents. Recently, keeping in pace with topical science, liquid crystals have entered into the fascinating domains of nanoscience and nanotechnology. This tutorial review describes the recent and significant developments in liquid-crystal nanoscience embracing contemporary nanomaterials such as nanoparticles, nanorods, nanotubes, nanoplatelets, etc. The dispersion of zero-, one- and two-dimensional nanomaterials in liquid crystals for the enhancement of properties, liquid-crystalline phase behavior of nanomaterials themselves, self-assembly and alignment of nanomaterials in liquid-crystalline media, and the synthesis of nanomaterials by using liquid crystals as ‘templates’ or ‘precursors’ have been highlighted and discussed. It is almost certain that the ‘fourth state of matter’ will play more prevalent roles in nanoscience and nanotechnology in the near future. Moreover, liquid-crystal nanoscience reflects itself as a beautiful demonstration of the contemporary theme “crossing the borders: science without boundaries”.

Liquid-crystal nanoscience: an emerging avenue of soft self-assembly

Triphenylene-based discotic liquid crystals, which have already been used commercially in phase compensation films to improve the viewing angle of liquid crystal display devices, also have application potential as one-dimensional charge carrier systems useful in electrical conduction, photoconduction, electroluminescence, photovoltaic solar cells, gas sensing, optical data storage and other devices. Over the past 25 years, more than 500 triphenylene derivatives have been synthesized to explore these possibilities. Cammidge and Bushby reviewed the chemistry and physical properties of about 100 triphenylene-based discotic liquid crystals prepared up to 1995. This review summarizes advances in the chemistry of triphenylene-based discotic liquid crystals since late 1995.

Recent developments in the chemistry of triphenylene-based discotic liquid crystals

The nematic phase of discotic liquid crystals, although rarely observed, has made very significant progress over the past three decades since their discovery. It has made its way from a mere scientific curiosity to application in commodities. The negative birefringence films formed by polymerized nematic discotic liquid crystals have been commercialized as compensation films to enlarge the viewing angle and enhance the contrast ratio of commonly used twisted nematic liquid-crystal displays. High strength and high performance carbon fibers for industrial applications have been obtained from the carbonaceous mesophase and a liquid-crystal display device with wide and symmetrical viewing angle has been demonstrated by using discotic nematic liquid crystals. Discotic films with patterned colours have been obtained from cholesteric lyo-mesophases of discotic liquid crystals. Various molecular architectures have been designed and synthesized to exhibit the discotic nematic phase over a wide range of temperature. This critical review focuses on the synthesis and physical properties of these fascinating materials. It deals with the structure of various nematic phases, different discotic cores exhibiting the nematic phase, novel designing and transition temperature engineering principles, alignment and physical properties, and finally the application of discotic nematic LCs as the active switching component and as optical compensation films for widening the viewing angle and contrast ratio of liquid-crystal display devices (98 references).

Discotic nematic liquid crystals: science and technology

Discotic liquid crystals are unique nanostructures with remarkable electronic and optoelectronic properties. Triphenylene derivatives play a major role in the research on discotic liquid crystals. Following recent reviews of the chemistry of triphenylene‐based monomeric liquid crystals, this article now reviews the chemistry and physical properties of triphenylene‐based discotic dimeric, oligomeric and polymeric liquid crystals.

Sandeep Kumar

Papers

Self-organization of disc-like molecules: chemical aspects

Liquid-crystal nanoscience: an emerging avenue of soft self-assembly

Recent developments in the chemistry of triphenylene-based discotic liquid crystals

Discotic nematic liquid crystals: science and technology

Triphenylene‐based discotic liquid crystal dimers, oligomers and polymers