- EFFECT OF THE REVERSAL OF THE CENTRAL SCHIFF'S BASE LINKAGE ON LIQUID CRYSTAL PROPERTIES: THE 4-PHENYLBENZYLIDENE-4 prime -n-ALKOXYANILINES AND 4-(4 prime -n-ALKOYXBENZYLIDENEAMINO)-BIPHENYLS.
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Twelve 4-phenylbenzylidene-4 prime -n-alkoxyanilines were prepared and their liquid crystal phases categorized. The properties of these compounds are compared with those of the analogous Schiff's bases, the 4-(4 prime -n-alkoxybenzylideneamino)biphenyls,
- Byron,Keating,O'Neill,Wilson,Goodby,Gray
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- Synthesis and mesomorphic properties of 2,4-bis(4′-n-pentyloxybenzoyloxy)- benzylidine-4″- n-alkoxyaniline
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The synthesis and mesomorphic properties of a new series of 2,4-bis(4′-npentyloxybenzoyloxy)- benzylidine-4″ -n-alkoxyaniline (DC5An) are reported. The molecular structure of compounds was confirmed by FTIR, 1H-NMR, 13C-NMR, mass spectroscopy and elemental analysis. The mesomorphic properties were studied by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM) measurements. All compounds of the series exhibit nematic (N) and smectic C (SmC) phases. The first four homologues (DC5A1-DC5A4) display a N mesophase, whereas the highest homologues (DC5A5-DC5A10) exhibit an enantiotropic dimorphism N and SmC phases. The mesomorphic properties of the present series are compared and discussed with other structurally related series.
- Hamad, Wali M.,Azeez, Hashim J.,Al-Dujaili, Ammar H.
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- Quinolines by three-component reaction: Synthesis and photophysical studies
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The synthesis of five quinolines 8-octyloxy-4-[4-(octyloxy)phenyl]quinoline and 6-alkoxy- 2-(4-alkoxyphenyl)-4-[(4-octyloxy)aryl]quinolines are described by three-component coupling reaction mediated by Lewis acid FeCl3 and Yb(OTf)3. 4-n-octyloxybenzaldehyde, anisaldehyde, 4-n-octyloxyaniline p-anisidine, and 1-ethynyl-4-heptyloxybenzene, 1-ethynyl-4-octyloxybenzene and 2-ethynyl-6-heptyloxynaphthalene are the reagents in this protocol. A Yb3+ catalyst resulted in higher yields of quinolines than Fe3+. Polarizing optical microscopy (POM) revealed that none of the quinolines were liquid crystals, even the more anisotropic. UV-Vis measurements of one of the quinolines in polar solvent show two absorption bands at 280 and 350 nm related to π,π?and n,π?transitions. No changes were observed to lower-energy absorption band (ε 4 mol L-1 cm-1) related to n,π?transition. A laser flash photolysis study for one of the quinolines relates a main transient band at 450 nm with a lifetime of 2.6 μs in ethanol, which is completely quenched in the presence of oxygen. This transient band was assigned to triplet-triplet absorption of one of the quinolines, which is semi-oxidised in the presence of phenol. Radiative rate constants have been determined along singlet and triplet excited state energies (3.39 and 3.10 eV, respectively). The chemical structure of one of the quinolines was also unequivocally confirmed by single-crystal X-ray analysis.
- Sales, Eric S.,Schneider, Juliana M. F. M.,Santos, Marcos J. L.,Bortoluzzi, Adailton J.,Cardoso, Daniel R.,Santos, Willy G.,Merlo, Aloir A.
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p. 562 - 571
(2015/03/14)
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- Liquid crystalline properties of dimers having o-, m- and p- positional molecular structures
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With the objective to design and synthesis of Schiff's base symmetrical liquid crystal dimmers and to study the effect of molecular structure variation (o-ortho, m-meta, p-para) and change in alkoxy terminal chain length on mesomorphic properties of liquid crystals, We have synthesized Schiff base dimers from dialdehyde derivative containing 2-hydroxy-1,3-dioxypropylene as short spacer with aniline derivatives having different lengths of terminal alkoxy chains (n = 5, 7, 9). The chemical structure of the final products was characterized by proton nuclear magnetic resonance (1H NMR) spectroscopy and fourier transform infrared (FT-IR) spectroscopy. The mesomorphic properties and optical textures of the resultant dimers were characterized by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The existence of smectic A phase transition was confirmed by the observation of batonnets and fan shaped textures in optical microscopy when compound were heated from crystalline phase. All of the dimers of this series, with the exception of 2S5 -ortho, -meta, -para, were thermotropic liquid crystal. The compound 2S9 -meta was monotropic, while the rest were enantiotropic. It was found that the change in terminal alkoxy chain length has pronounced effect on the mesomorphic properties. The temperature range of smectic A phase window widens with increasing alkoxy chain length.
- Park, Joo-Hoon,Choi, Ok-Byung,Lee, Hwan Myung,Lee, Jin-Young,Kim, Sung-Jo,Cha, Eun-Hee,Kim, Dong-Hyun,Ramaraj,So, Bong-Keun,Kim, Kyung-Hwan,Lee, Soo-Min,Yoon, Kuk Ro
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experimental part
p. 1647 - 1652
(2012/07/27)
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- Liquid-crystalline polymorphism of 4-heptyloxybenzylidene-4′- alkyloxyanilines and their phase equilibrium with 4-octyloxyphenyl 4-nitrobenzoate
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This paper describes the synthesis and liquid-crystalline properties of the homologous series of 4-heptyloxybenzylidene-4′-alkyloxyanilines (7-n). Six of them are presented for the first time. Based on the polarization microscopy (POM and TOA methods) and the calorimetric (DSC) measurements following polymorphism has been detected: nematic, smectic C and smectic I mesophases. The presence of these mesophases was confirmed by the miscibility method, using 4-octyloxyphenyl 4-nitrobenzoate and terephtal-bis (4-butyloaniline) as a mesophase references. Extraordinary results have been found in the mixtures of the investigated compounds with 4-octyloxyphenyl 4-nitrobenzoate; Induced smectic A has been observed, which is connected with very strong intermolecular interactions. Additionally destabilization of nematic and smectic C phases was visible.
- Godzwon, Joanna,Sienkowska, Monika J.,Galewski, Zbigniew
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scheme or table
p. 75 - 82
(2012/04/04)
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- The synthesis and NLO properties of 1,8-naphthalimide derivatives for both femtosecond and nanosecond laser pulses
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Four 1,8-naphthalimide derivatives were synthesized for new nonlinear optical(NLO) materials. Hydrazone group as a p-π structure was introduced into the molecule to extend conjugation and produce NLO properties. Their linear and nonlinear optical (NLO) properties were studied in details. The results show that these compounds possess strong excited-state absorption (ESA) properties and optical limiting with nanosecond laser pulses at 532 nm. Moreover, they also preserve the luminescence originated from naphthalimide and two-photon absorption (TPA) behaviour which can be observed under femtosecond laser pulses ranged from 750 to 870 nm. The broad-band optcial limiting properties of these compounds indicate that they can be potentially applicated in optical limiting materials.
- Ye, Gao-Jie,Zhao, Ting-Ting,Jin, Zheng-Neng,Gu, Pei-Yang,Mao, Jia-Yuan,Xu, Qing-Hua,Xu, Qing-Feng,Lu, Jian-Mei,Li, Na-Jun,Song, Yin-Ling
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scheme or table
p. 271 - 277
(2012/05/04)
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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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- Electro-optical switching studies on 1,3-phenylene based banana shaped liquid crystals
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This work deals with the study of the thermotropic liquid crystalline properties of new asymmetric bent core liquid crystals. The thermotropic properties was analyzed by polarized optical microscopy, differential scanning calorimetric analysis and variable temperature X-ray diffraction measurements. Effect of equal terminal chain with asymmetric bent core system on mesomorphic behavior was examined. The shorter methyl chain compound 10a of exhibits B 1 mesophase and higher homologs (10b and 10c) shows antiferroelectric B2 mesophases, which was studied by electro-optical measurements.
- Balamurugan,Kannan,Yadupati,Roy
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p. 118 - 124
(2011/10/03)
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- Synthesis of symmetric liquid crystal dimers based on azo and imine groups and investigation of phase behaviour by varying alkoxy terminal chain length
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With the objective to study the effect of alkoxy terminal chain length on mesomorphic properties of liquid crystals, we have synthesized two (Azo and Imine) different series of dimesogens by varying terminal alkoxy chain length (n = 6-12) with a short spacer unit in between two mesogens. Transition temperatures and phase characterization were studied by DSC, POM and XRD analysis. It was found that all the dimers show mesomorphic properties and the change in terminal alkoxy chain length has pronounced effect on the smectic phase window. In the DSC cooling scan, the smectic phase window of azo compounds increased from 6.4°C (2A6) to 16.0°C(2A12), whereas in Schiff base compounds, it increased from 9.2°C (2S6) to 31.0°C(2S12). Further, the 2A11 dimer was found to undergo photo induced configurational changes.
- Kim, Tae Hyeong,Lee, Chang Sin,Ramaraj,Jeon, Hye Jin,Song, Hyun Hoon,Lee, Soo Min,Yoon, Kuk Ro
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experimental part
p. 102 - 116
(2010/03/04)
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- Synthesis and liquid crystalline properties of novel triazene-1-oxide derivatives
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A new group of compounds, C6H5-N(O)=N-NH-C6H4-C(O)-O-C6H4-CH=N-C6H4-OR, (1), [R=n-alkyl group; 1a (R=C7H15 ) to 1h (R=C14H29)], has been designed and synthesized to develop triazene-1-oxide based liquid crystals. All the compounds have been characterized on the basis of their spectral data. Their thermal behavior has been examined and found to exhibit thermotropic liquid crystalline behavior over a wide range of temperature. All members of this family uniformly show nematic phase behavior on melting up to the clearing point during heating as well as on phase entering up to the solidification during cooling. An odd-even effect on transition temperatures has been observed during heating as well as cooling.
- Das, Purak,Biswas, Achintesh Narayan,Bandyopadhyay, Pinaki,Mandal, Pradip Kumar
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scheme or table
p. 3 - 15
(2010/03/24)
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- Smectic polymorphism of 4-nonyloxybenzylidene-4′-alkyloxyanilines
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This paper describes liquid-crystalline polymorphism of the homologous series of 4-nonyloxybenzylidene-4′-alkyloxyanilines. Based on the polarization microscopy (POM, TOA) and the calorimetric (DSC) measurements the following mesophases were detected: nematic, smectic A, smectic C, smectic B, smectic I and smectic G. The presence of these mesophases was confirmed by the miscibility method, using: 4-heptyloxybenzilidene-4′-pentylaniline, 4-hexyl-4′-decyloxyazobenzene and 4-nonyloxybenzilidene-4′-butylaniline as mesophase references. Influence of the alkyl chain length on the type of mesophases and entropic effects of phase transition are discussed.
- Godzwon, Joanna,Sienkowska, Monika J.,Galewski, Zbigniew
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p. 259 - 267
(2008/03/13)
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- Synthesis and absorption properties of zinc-phthalocyanineswith photoresponsive azobenzene groups
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The phthalocyanines (1) and (2) with eight photoisomerizableazobenzene groups have been synthesized and spectroscopically characterized. These macrocycles exhibit partial trans-cis isomerzation properties upon irradiation of UV/VIS light.
- Han, Ki-Jong,Kay, Kwang-Yol
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p. 2869 - 2874
(2007/10/03)
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- Mesogenicity of organophosphazenes: The effect of phosphazene rings and side groups on the phase transition
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Cyclotriphosphazene and cyclotetraphosphazene derivatives with mesogenic 4-N-(4-alkoxyphenyl)iminomethyl)phenoxy and 4-(4′-alkoxy) biphenoxy moieties were synthesized. Schiff base moiety has higher mesomorphic stability than that in biphenyl moiety both in cyclotriphosphazene and cyclotetraphosphazene. Cyclotriphosphazenes possess higher thermal stability in the mesomorphic phase than the cyclotetraphosphazenes, suggesting the difference in the molecular structure.
- Moriya, Keiichi,Yamane, Toshihiro,Suzuki, Toshiya,Masuda, Tsuyoshi,Mizusaki, Hiroshi,Yano, Shinichi,Kajiwara, Meisetsu
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p. 1427 - 1432
(2007/10/03)
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- Mesogenic 4-(2,3-Epoxypropoxy)-4'-alkoxyazoxybenzenes
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Optimal conditions for preparation of 4-(2,3-epoxypropoxy)-4'-alkoxyazoxybenzenes were developed, and 10 mesogenic homologs (n = 1-10) possessing an extended nematic mesophase were synthesized.Nonyloxy and decyloxy derivatives of epoxyazoxybenzene exhibit also smectic mesomorphism.
- Burmistrov, V. A.,Kuz'mina, S. A.,Koifman, O. I.
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p. 351 - 353
(2007/10/03)
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