• B K Sadashiva

      Articles written in Pramana – Journal of Physics

    • Liquid crystals of disc-like molecules

      S Chandrasekhar B K Sadashiva K A Suresh

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      Thermotropic mesomorphism has been observed in pure compounds consisting of simple disc-like molecules, viz., benzene-hexa-n-alkanoates. Thermodynamic, optical and x-ray studies indicate that the mesophase is a highly ordered lamellar type of liquid crystal. Based on the x-ray data, a structure is proposed in which the discs are stacked one on top of the other in columns that constitute a hexagonal arrangement, but the spacing between the discs in each column is irregular. Thus the structure has translational periodicity in two dimensions and liquid-like disorder in the third.

    • Miscibility studies of disc-like molecules

      J Billard B K Sadashiva

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      The total miscibility method is applied to study the recently discovered mesophases of disc-like molecules, benzene-hexa-n-alkanoates. These compounds do not form continuous solid solutions, but are totally miscible in the liquid and mesomorphic states. The virtual mesophase-isotropic transition temperature for the hexanoate compound derived from the miscibility diagram is in excellent accord with that obtained from the previously reported pressure-temperature phase diagram. With simplifying assumptions, it is possible to predict with acceptable reliability the isobaric binary phase diagrams of any two members of the series. The real and virtual mesophase-liquid transition temperatures are linear functions of the molecular weight. On the other hand, a plot of the crystal-liquid transition temperatures versus the molecular weight exhibits a minimum. Total miscibility in the mesomorphic state is not observed for two members of different discogenic series, but the existence of different mesophase types is not proved. Lyotropic mesomorphism for a disc-like mesophase is established.

    • Paramagnetic nematic liquid crystals

      S Chandrasekhar B K Sadashiva S Ramesha B S Srikanta

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      The paper reports new nematic liquid crystals that are paramagnetic.

    • Molecular structure and chiral liquid crystalline phases

      B K Sadashiva

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      We describe briefly some results obtained on both chiral and achiral compounds exhibiting chiral mesophases. We report the first example of a single component system exhibiting the undulated twist grain boundary C* or UTGBC* phase. Preliminary results concerning a few achiral compounds composed of banana-shaped molecules exhibiting a mesophase is reported. They have been investigated by polarized light optical microscopy, differential scanning calorimetry and x-ray diffraction studies.

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