- Synthesis, liquid crystalline properties and photo switching properties of coumarin-azo bearing aliphatic chains: Application in optical storage devices
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A series of novel azo-coumarin derivatives with different aliphatic chain length (3a-e) have been synthesized and characterized for liquid crystal properties and their photoswitching behavior. The incorporation of coumarin along with azobenzene was prepared via esterification reaction and differ in the length of alkyl group, CnH2n+1, where n = 6, 8, 10, 12 and 14. Azo-coumarin bearing C14 alkyl chain shows Smectic–A phase while azo-coumarin bearing rest of long alkyl chain exhibited Nematic phase. The incorporation of natural product moieties into azobenzene network has increased electron delocalisation and liquid crystal properties. The photoswitching properties of said molecules were tested and the coumarin-azo compounds 3a-e took ~46 s to reach photostationary state during UV illumination and exhibited long thermal back relaxation time (~16 h) in solutions. Device is also fabricated to see the performance of the device with respect to the alkyl chain length. Presented studies show the importance of azo-coumarin derivatives with different chain length for the application of optical storage devices.
- Madiahlagan, Eswaran,B N, Sunil,Ngaini, Zainab,Hegde, Gurumurthy
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- Columnar self-assembly of bowl shaped fluorescent liquid crystals based on calix[4]arene with Schiff base units
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A new family of bowl-shaped molecules with a calix[4]arene rigid core and appended on four-sides, that display a wide range of hexagonal columnar phases, has been synthesised and well characterized. The thermal behaviours of the present compounds were established using a combination of polarising optical microscopy (POM), differential scanning calorimetry (DSC) and a high-temperature powder X-ray diffraction method (XRD). It is found that all of the synthesised materials show an enantiotropic hexagonal columnar liquid crystal phase. The structural and conformation characterization of these newly synthesised compounds was achieved by FT-IR, 1H NMR, and 13C NMR spectroscopy. All of the synthesised compounds exhibited good blue luminescence in solution under long wavelength UV light. To explore the structure property correlations, the alkoxy side chain group was varied from a lower alkyl spacer to a higher alkyl spacer on the lower rim of the calix[4]arene. The present research specified that the introduction of linking groups on the lower rim with an n-alkoxy side group is an influential approach to obtaining a supramolecular bowl shape liquid crystal which has good thermal and photophysical behaviour.
- Sharma, Anuj S.,Sharma, Vinay S.,Vekariya, Rajesh H.
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supporting information
p. 15044 - 15051
(2018/09/29)
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- Designer ionic liquid crystals based on congruently shaped guanidinium sulfonates
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Ionic liquid crystals are mesogenic compounds that consist of cations and anions, usually rod-like cations and spherical anions. Herein we report a new method for the synthesis of ionic liquid crystals by using cations and anions of the same molecular shape with oppositely charged head groups. Thus, 4-alkoxyphenylpentamethylguanidinium 4-alkoxyphenylsulfonate ion pairs have been synthesised. 4-Alkoxyphenylpentamethylguanidinium iodides were also prepared to determine the influence of congruently shaped anions, in comparison with their spherical counterparts, on mesophase behaviour, which was investigated by differential scanning calorimetry (DSC), polarising optical microscopy (POM) and X-ray diffraction (XRD). All the liquid crystalline salts exhibit smectic A mesophases with strongly interdigitated bilayer structures. The guanidinium sulfonate ion pairs show mesomorphic properties from shorter alkyl chain lengths (≥C9) and lower melting points (≈10 K), whereas the corresponding guanidinium iodides are liquid crystalline for longer alkyl chain lengths (≥C14). For chains with ≥C18, however, the mesophase range decreases for the sulfonate ion pairs, but not for the iodide salts. Tuning mesophase stability: Guanidinium sulfonate ion pairs with congruently shaped anions and cations with short alkyl chains R (see scheme) have favourable mesogenic properties with respect to mesophase stability in comparison with their guanidinium counterparts with spherical iodide anions. Copyright
- Butschies, Martin,Frey, Wolfgang,Laschat, Sabine
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supporting information; experimental part
p. 3014 - 3022
(2012/04/10)
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- A molecular insight on the supramolecular assembly of thiophene polymers
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Herein, the relationship between supramolecularly self-assembled microstructures and the chemical structures of photoluminescent molecules is discussed. A series of non-amphiphilic molecules with different length alkyl chains (4-14), central mesogenic groups, and chemical linkers were designed and synthesized. Intricate analysis shows that the supramolecular assembly varies with change in torsion angle of the thiophene linking group on elongation of the alkyl chain. Small angle X-ray scattering measurement shows long range molecular interaction for lower alkyl chain length, AFM reveals circular domains for octyl and decyl alkyl group polymers. UV-Visible and photoluminescence studies in solution and thin-film show that the J-aggregate patterns for the circular domain of the polymer backbone has a major effect on the polymer absorbance, and produces a larger shift for the photoluminescence signals at higher wavelengths. Excitation polarisation studies show a change in molecular ordering in various colour regions with change in aggregation by means of maximum dichroic ratio for the circular domain assembly. Charge carrier mobility and cyclic voltammetry studies show higher mobility and reduced band gap for these circular domain polymers. Dynamic light scattering studies of octyl alkyl chain polymers show a bimodal distribution, which shows the apparent nature of anisotropy in solution. The Royal Society of Chemistry.
- Suryanarayanan, Chandrasekaran,Ravindran, Ezhakudiyan,Ananthakrishnan, Soundaram Jeevarathinam,Somanathan, Narayanasastri,Mandal, Asit Baran
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p. 18975 - 18982
(2012/10/29)
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- Studies of calamitic liquid crystalline compounds involving ester-azo central linkages with a biphenyl moiety
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Two mesogenic homologous series involving ester-azo central linkages with a biphenyl moiety have been synthesized, such as 4'-[(4-n-alkoxyphenyl)diazenyl] biphenyl-4-ol (series I) and 4'-[(4-n-alkoxyphenyl) diazenyl]-4-butoxy phenyl biphenyl-4-carboxylate (series II). Azobiphenyl of series I having a free hydroxyl group with strong hydrogen bonding exhibits a high-temperature enantiotropic smectic phase. Whereas in series II, compounds containing C 1-C8 carbon atoms exhibit only a monotropic smectic phase and compounds with C10, C12, C14, and C 16 atoms show an enantiotropic smectic phase. These compounds were characterized by elemental analysis, FT-IR, 1H-NMR, and mass spectral studies. The phase transition and mesogenicity of these substances were studied by polarizing optical microscopic and differential scanning calorimetric techniques. Their thermal stabilities and other characteristics are discussed. Copyright Taylor &Francis Group, LLC.
- Thaker,Dhimmar,Patel,Solanki,Patel,Chothani,Kanojiya
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experimental part
p. 172 - 191
(2012/07/27)
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- Role of terminal heterocyclic ring on mesomorphic properties of homologous series
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Two new homologous series of compounds with a heterocyclic ring having sulfur and oxygen as a hetero atom derived from p-hydroxy acetophenone and alkoxy aniline containing cinnamate-azomethine as central linkages have been synthesized. viz. 4(furalacryloxy) α-methyl benzylidine-4′-alkoxy aniline and 4(thianylacryloxy) α-methyl benzylidine-4′-alkoxy aniline. The compound of both the series have been characterized by elemental analysis, FT-IR, 1H-NMR, and mass spectrometry method. Their liquid crystalline properties have been investigated by optical polarizing microscopy and differential scanning calorimetry (DSC) studies. All the derivatives are mesomorphic in nature showing the nemetic phase. The mesomorphic properties of the present two series are compared with other structurally related series to evaluate the effect of thiophene and furan on mesomorphism. Copyright Taylor & Francis Group, LLC.
- Thaker,Patel,Solanki,Dhimmer,Dave
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experimental part
p. 63 - 80
(2010/09/05)
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