Showing papers by "S. Chandrasekhar published in 1988"
TL;DR: In this paper, optical studies have been carried out on a nematogenic copper complex, which incorporates the features of both rod-like and disk-like molecules, and conoscopic figures have been presented demonstrating the occurrence of a biaxial nematic phase in the pure complex, the uniaXial-biaxial (Na-Nb) transition in binary mixtures, and the temperature variation of the biaaxiality near this transition.
Abstract: Optical studies have been carried out on a nematogenic copper complex, which incorporates the features of both rod-like and disk-like molecules. Conoscopic figures are presented demonstrating (i) the occurrence of a biaxial nematic phase in the pure complex, (ii) the uniaxial-biaxial (Na-Nb) transition in binary mixtures, and (iii) the temperature variation of the biaxiality near this transition. The I-Na-Nb phase diagram has been studied for the binary system.
105 citations
TL;DR: In this paper, a biaxial nematic liquid crystal was found in a simple thermotropic system, where the liquid crystal is a bao-nematic liquid.
Abstract: We report a biaxial nematic liquid crystal in a simple thermotropic system.
51 citations
TL;DR: In this article, 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, and 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.
Abstract: 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.
14 citations
TL;DR: In this article, a method of improving the accuracy of determination of enthalpies of liquid crystalline transitions by differential scanning calorimetry is presented, which involves measurements at different heating rates and interpolation to zero heating rate.
Abstract: We demonstrate a simple practical method of improving the accuracy of determination of enthalpies of liquid crystalline transitions by differential scanning calorimetry. The method involves measurements at different heating rates and interpolation to zero heating rate.
5 citations
TL;DR: In this paper, the nematic-isotropic (NI) and crystalnematic (KN) transition temperatures were measured from atmospheric pressure to 1 kbar for a homologous series of thermotropic polyesters based on regularly alternating 2,2'-dimethylazoxybenzene mesogen and alkanedicarboxylic acid spacer.
Abstract: Abstract. The nematic-isotropic (NI) and crystalnematic (KN) transition temperatures were measured from atmospheric pressure to 1 kbar for a homologous series of thermotropic polyesters based on regularly alternating 2,2'-dimethylazoxybenzene mesogen and alkanedicarboxylic acid spacer. The values of (dP/dT) for the NI transitions show an odd-even alternation with n, consistent with the previously reported alternation of TNI and (ΔH)NI. The characteristic temperature T* calculated for n = odd is approximately 300 K, similar to the values for noncybotactic nematics. On the other hand, for n =even, T* could not be reliably calculated, perhaps due to the existence of cybotactic ordering. At the KN transition there is no such clear alternation in (dP/dT). The specific volume changes (ΔV)KN at melting are very small and comparable in magnitude with (ΔV)NI. They are much smaller than the corresponding values for low molar mass liquid crystals and conventional polymers. This suggests that the crystals of...
3 citations