178758-43-5Relevant academic research and scientific papers
Room temperature helical fluids in single-component systems
Shanker,Bindushree,Chaithra,Pratap,Gupta, Ravindra Kumar,Achalkumar,Yelamaggad
, p. 849 - 858 (2019)
Technologically significant chiral nematic (N*) phase is a helicoidal superstructure, that is generally formed by the spontaneous self-assembly of entire chiral mesogens (mostly calamitics) or by the LC mixtures where a chiral dopant is being added to the
Effect of regioisomerism on the self-assembly, photophysical and gelation behavior of aroylhydrazone based polycatenars: Synthesis and characterization
Kanth, Priyanka,Singh, Hemant Kumar,Kumar, Vijay,Singh, Sachin Kumar,Rao, D.S. Shankar,Prasad, S. Krishna,Singh, Bachcha
, (2019/07/02)
In this paper we report five series of aroylhydrazone based polycatenars differing from each other in number and position of alkoxy chains on one end of the core; keeping other end the same. A systematic variation in the structures was carried out to understand the effect of position and chain length on the mesophase behavior. In the case of single alkoxy chain at 4-position, there is a transition from Smectic C to Smectic A mesophase during cooling and Smectic A to Smectic C transition in heating cycle in all the homologues except n = 6 & n = 8. In the case of two alkoxy chains at 3-, 5-positions, the compounds are non-mesogenic in nature. On changing the position of alkoxy chains from 3-, 5-positions to 3-, 4-positions, intermolecular forces weaken and these compounds become liquid crystalline and show columnar rectangular mesophase resulting from the effect of regioisomerism. Moving on to the series with three alkoxy chains, it was observed that 2-, 3-, 4-trialkoxy substituted compounds exhibit columnar rectangular mesophase except lower chain length (n = 6 & 8) while 3-, 4-, 5-trialkoxy substituted aroylhydrazones show columnar rectangular mesophase; except n = 10 which shows columnar oblique mesophase. Thus it was established that on increasing density of alkoxy chains around one terminal, mesophase changes from smectic to columnar mesophase. Temperature dependent Raman studies confirm the presence of intermolecular hydrogen bonding. Further, effect of substitution pattern did not show much influence on the photophysical properties of the mesogenic series in solid and solution state. However, the non-mesogenic series showed a different absorption and emission transition from the mesogenic series in solid and solution state. Solid state fluorescence studies show almost similar emission maxima in all the series. However, it was also noticed that non-mesogenic series show maximum red shifted emission maxima in solid state as compared to that of solution. All the series showed good gelation properties with less than 1% CGC (wt%) suggesting the strong ability of molecules to form gel. These H-bonded liquid-crystalline gels have immense potential for applications in emissive displays.
Tuning the thermotropic properties of liquid crystalline p-substituted aroylhydrazones
Singh, Hemant Kumar,Singh, Sachin Kumar,Nandi, Rajib,Singh, Madan Kumar,Kumar, Vijay,Singh, Ranjan K.,Rao, D. S. Shankar,Prasad, S. Krishna,Singh, Bachcha
, p. 44274 - 44281 (2015/06/02)
The synthesis and mesomorphic properties of forty substituted aroylhydrazones with peripheral mono-, di- and tri- alkoxy chains derived from a p-amino aroylhydrazone core are described. The compounds with two side chains exhibited a smectic A phase, while the compounds with six soft alkoxy side chains at symmetrical positions formed a rectangular columnar mesophase. The structures of these mesophases were confirmed by differential scanning calorimetry (DSC) analysis, polarized optical microscopy (POM) and powder X-ray diffraction (XRD) studies. Raman studies with the help of density functional theory on some of the mesogenic members have been performed to understand the changes in the intermolecular interactions during phase transitions. A structure-property relationship has been deduced, and mesogenic properties are found to be dependent on the chain length, density and position of the alkoxy chains around the molecular core.
Liquid-crystalline complexes of palladium(II) and platinum(II) with di- and tri-alkoxystilbazoles: Ligand control of mesomorphism
Donnio, Bertrand,Bruce, Duncan W.
, p. 2745 - 2755 (2007/10/03)
Liquid-crystalline complexes of palladium and platinum are formed when the metals are complexed to stilbazoles (4-styrylpyridines) bearing either two or three alkoxy chains. The complexes, termed polycatenar, show smectic C mesophases for most 3,4-disubstituted ligands, while the use of trisubstituted ligands leads to complexes showing columnar organisation, demonstrating that the spatial organisation of the metals in the liquid-crystal mesophase can be rather readily controlled. Complexes of these di- and tri-substituted stilbazoles with a cis-dicarbonylchloroiridium(I) fragment were not liquid crystalline.
