Hari Krishna Bisoyi

Carbon nanotubes in triphenylene and rufigallol-based room temperature monomeric and polymeric discotic liquid crystals

In this article, after a brief account of the work carried out in the area of dispersion of carbon nanotubes in liquid crystals, we present the dispersion of functionalized single-wall carbon nanotubes in novel room temperature liquid crystalline discotic monomers and polymers. The effect of nanotubes on phase behavior of electron-rich triphenylene derivatives and electron-deficient anthraquinone derivatives has been investigated. Mesophase behavior of the composites with nanotubes has been studied by polarizing optical microscopy, differential scanning calorimetry and X-ray diffractometry. Inclusion of carbon nanotubes into the columnar matrix does not destroy the mesophase of the host compounds but the columnar to isotropic transition temperatures decrease with increase in the quantity of carbon nanotubes in both monomeric and polymeric discotic liquid crystals.

Room-temperature electron-deficient discotic liquid crystals: facile synthesis and mesophase characterization

Two novel series of rufigallol-based room-temperature discotic liquid crystals have been designed and synthesized using microwave dielectric heating within a few minutes in good yield. The chemical structures of all the compounds have been characterized using spectral techniques and elemental analysis. The mesophase behaviors of all the compounds have been investigated by polarizing optical microscopy and differential scanning calorimetry. Columnar hexagonal structure of the mesophase of these compounds has been established with the help of X-ray diffraction studies.

Microwave-assisted facile synthesis of liquid-crystalline alkoxycyanobiphenyls and their dimers

An efficient, simple, rapid, and economically and environmentally acceptable microwave-assisted ‘green chemistry’ approach to the synthesis of various liquid crystalline alkoxycyanobiphenyls and their dimers is reported. The protocol provides high yields of all the products. While the phase transition temperatures of monomers were found to be identical with literature data, the phase transition temperatures of all the dimers were found to be slightly higher than the reported values and thus demonstrate the cleanness of the procedure.

Novel banana-discotic hybrid architectures.

Summary Here we present the design and synthesis of novel banana-discotic dimers and banana-bridged discotic dimers. The chemical structures have been characterized by spectral techniques and elemental analysis. The thermal behaviors of the compounds have been investigated by polarizing optical microscopy and differential scanning calorimetry. None of these synthesized compounds exhibit any liquid crystalline property probably because of the incompatibility of the bent-core with the discotic core.

Green Chemistry Approach to the Synthesis of Liquid Crystalline Materials

This article presents a simple, rapid, economic and environmentally acceptable microwave promoted “green chemistry” approach to the synthesis of some conventional and non-conventional liquid crystalline materials. Alkylation of 4′-hydroxy-4-biphenylcarbonitrile with various alkyl halides under microwave irradiation furnished alkoxycynobiphenyl-based calamitic liquid crystals in very high yield within one minute. Similarly, terminally-functionalized alkoxycyanobiphenyls and alkoxycyanobiphenyl dimers can also be prepared. Microwave irradiation of hexaalkoxytriphenylene in the presence of ionic liquids gives monohydroxy-pentaalkoxytriphenylene in about 30% yield. Novel imidazolium-based ionic liquid crystalline dimers can be easily prepared via quaternization reaction using microwaves. Classical reaction conditions failed to produce these dimers.