A Room-Temperature Discotic Nematic Liquid Crystal

Kumar, Sandeep; Varshney, Sanjay K.

doi:10.1002/1521-3773(20000901)39:17<3140::aid-anie3140>3.0.co;2-g

Cited by 124 publications

(57 citation statements)

References 21 publications

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“…Hexakis(4-nonylphenylethynyl)benzene (6) was prepared following the procedure reported earlier [9], and the scheme is shown in Fig. 1.…”

Section: Synthesismentioning

confidence: 99%

“…Several hexaalkynylbenzenes have been prepared and studied extensively. Efforts have been made to stabilize the discotic nematic phase of these materials at ambient temperature by changing peripheral substitutions [9][10][11]. Hexakis(4-nonylphenylethynyl)benzene (6) is a unique substance that forms a discotic nematic phase at moderate temperatures ranging from 68 to 83 C [12].…”

Section: Introductionmentioning

confidence: 99%

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Effect of Slow Cooling on a Discotic Nematic Liquid Crystal: Evidences for Nematic–Nematic Transitions

Vijayaraghavan

Kumar

2006

Molecular Crystals and Liquid Crystals

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There is considerable interest in discotic liquid crystals because of their possible applications in liquid crystal displays and in one-dimensional conductors. In view of these applications, knowledge and control of their phase behavior and transition temperatures are crucial. We have studied a discotic nematic liquid crystal, namely, hexakis(4-nonylphenylethynyl)benzene. The phase sequence reported for this sample on cooling is isotropic (I) 81.8 C discotic nematic (N D ) and 39 C crystal (Cr). The phase sequences were obtained using differential scanning calorimetry (DSC) and optical polarizing microscopy (OPM) studies while varying the sample temperature rapidly (5 C=min). However, on slowly cooling the sample (0.36 C=min), we observed anomalous optical textures and DSC peaks in the nematic region at 75 C and 52 C. We also find discontinuous changes in the optical transmission intensity and diamagnetic anisotropy in the vicinity of these temperatures on slow cooling. Further, the XRD pattern showed small but distinct shifts in the lateral (100) peaks in the vicinity of these transitions. We infer that the variations in the lateral distance between the discotic molecules may be responsible for these observed nematic-nematic (N-N) transitions.

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“…Hexakis(4-nonylphenylethynyl)benzene (6) was prepared following the procedure reported earlier [9], and the scheme is shown in Fig. 1.…”

Section: Synthesismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of Slow Cooling on a Discotic Nematic Liquid Crystal: Evidences for Nematic–Nematic Transitions

Vijayaraghavan

Kumar

2006

Molecular Crystals and Liquid Crystals

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“…In order to achieve this apposite isotropisation as well as melting temperature, various methods have been suggested in the literature, which include branching [23,24,[25][26][27][28][29][30][31][32][33][34][35], unsaturation [24], heteroatom substitution [36][37][38] etc. Assorted examples in the literature have shown the effect of branching on melting and isotropic temperatures.…”

Section: Introductionmentioning

confidence: 99%

“…The introduction of branched chains not only softens these C 60 -based materials but also enables the formation of thermotropic LCs and liquids that are nonvolatile at room temperature [32]. Kumar et al synthesised several branched chain substituted benzene hexa-and penta-alkynes which show very broad range of discotic nematic mesophase, stable well below and above the room temperature [33,34]. The decrease in transition temperatures could be due to the steric effect of the branch (disorderness) and the reduction in symmetry associated with them.…”

Section: Introductionmentioning

confidence: 99%

Microwave-assisted synthesis of novel mixed tail rufigallol derivatives

et al. 2013

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Microwave-assisted syntheses of five new series of rufigallol-based mesogens are reported with branched alkyl chains at the peripheral positions. The chemical structures of these newly synthesised compounds were determined by 1 H nuclear magnetic resonance (NMR), 13 C NMR, infrared spectroscopy, ultraviolet spectroscopy and elemental analysis. The thermotropic liquid crystalline properties were investigated by polarising optical microscopy (POM), differential scanning calorimetry and X-ray diffractometry. Most of the derivatives were found to be liquid crystalline over a wide temperature range.

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“…For these compounds, the rotational freedom of the ethynyl linkers results in non-planar conformations, which reduce interdisc interactions and efficient stacking of the discs, thus preventing the formation of columnar phases. Nematic discotic materials are used as compensating films that find application for improving the viewing angle of liquid crystalline displays [10].…”

Section: Introductionmentioning

confidence: 99%

A columnar mesophase with high lateral order from a triphenylene-hexa(3,5-dialkoxy)benzoate

et al. 2010

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This paper describes the synthesis of triphenylene-2,3,6,7,10,11-hexayl hexakis(3,5-dialkoxy)benzoates, bearing hexyloxy (1a) and dodecyloxy tails (1b). These benzoate esters were synthesised in high yields by employing a DCC coupling of the (3,5-dialkoxy) benzoic acid to 2,3,6,7,10,11-hexahydroxytriphenylene. The 3,5-dihexyloxy benzoate 1a, forms a highly ordered columnar mesophase with extensive lateral and very limited columnar order, whereas no mesomorphic phases were observed for the 3,5-didodecyloxy benzoate 1b. In contrast with most benzoate esters of triphenylene, nematic mesophases were not observed for 1.

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A Room-Temperature Discotic Nematic Liquid Crystal

Cited by 124 publications

References 21 publications

Effect of Slow Cooling on a Discotic Nematic Liquid Crystal: Evidences for Nematic–Nematic Transitions

Effect of Slow Cooling on a Discotic Nematic Liquid Crystal: Evidences for Nematic–Nematic Transitions

Microwave-assisted synthesis of novel mixed tail rufigallol derivatives

A columnar mesophase with high lateral order from a triphenylene-hexa(3,5-dialkoxy)benzoate

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