- [1,2,3]-triazole derivatives: Mesomorphic property dependence on the molecular shape
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Nowadays, heterocyclic units have been extensively studied for the preparation of thermotropic liquid crystals due to their ability to impart lateral and/or longitudinal dipoles and induce changes in molecular shape. Key parameters to accede to stable mesophases are the position of the heterocycle and the nature of terminal and linking functions. We present in this paper, an overview of several series of 1,2,3-triazole liquid crystalline derivatives that we designed and characterized. We highlight the effect of different connecting functions and the geometry of mesogenic core on the mesomorphic behavior of these derivatives.
- Benallou, Souria,Saidi-Besbes, Salima,Grelet, Eric,Bentaleb, Ahmed
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- Facile synthesis of organo-soluble surface-grafted all-single-layer graphene oxide as hole-injecting buffer material in organic light-emitting diodes
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Graphene oxide (GO) was modified by surface grafting and the product P-GO exhibited a surprisingly good solubility in common solvents (as high as 1.8 mg mL-1 in DMF) without sonication and can be spin coated to form large single-layer sheets on a substrate. In contrast to GO, all-single-layer P-GO sheets are readily formed in solution, which are highly useful for separation from other multi-layer sheets and as precursors to all-single-layer graphene. The unique property of single-layer P-GO made it a promising functional material, such as hole-injecting buffer (HIB) material in organic light-emitting devices. The devices using P-GO as a hole-injecting buffer layer on the ITO electrode perform better than those with PEDOT:PSS.
- Zhong, Ze,Dai, Yanfeng,Ma, Dongge,Wang, Zhi Yuan
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- New long-chain donor-acceptor-donor pyromellitic diimide (PMDI) derivatives. A combined theoretical and experimental study
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This study involves the electrochemical, thermal and photophysical profiling of new pyromellitic diimide (PMDI) derivatives containing alkyl chains of different sizes. The photophysical investigation shows that all compounds exhibited absorption in the UV-B region (～290 nm). The band-gaps were calculated by onset peak values of around 4.03 eV. The compounds are photoactive in the UV-A region (312–328 nm) with a small solvatochromic effect in the excited state (Δλem = 16 nm). The electrochemical studies revealed that the reduction of the bisimide moiety showed two waves due to the formation of both the radical anion and a dianion. On the other hand, oxidation showed two waves due to the formation of radical cations and dications. The thermal properties were measured by differential thermal analysis (DTA) and thermogravimetric analysis (TGA), and the materials showed high thermal stability (Td > 300 °C). Theoretical calculations were also performed to study the geometry and charge distribution of these compounds in their ground and excited electronic states. No significant changes in the absorption and emission maxima were found by changing the solvent or substituents attached to the PMDI structure.
- Dal-Bó, Alexandre Gon?alves,da Costa Duarte, Rodrigo,Cercená, Rodrigo,Peterson, Michael,Rafique, Jamal,Saba, Sumbal,Zapp, Eduardo,Gil, Eduarda Sangiogo,Bruno Gon?alves, Paulo Fernando,Rodembusch, Fabiano Severo,Frizon, Tiago Elias Allievi
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- Thermotropic Liquid-Crystalline and Light-Emitting Properties of Bis(4-aalkoxyphenyl) Viologen Bis(triflimide) Salts
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A series of bis(4-alkoxyphenyl) viologen bis(triflimide) salts with alkoxy chains of different lengths were synthesized by the metathesis reaction of respective bis(4-alkoxyphenyl) viologen dichloride salts, which were in turn prepared from the reaction of Zincke salt with the corresponding 4-n-alkoxyanilines, with lithium triflimide in methanol. Their chemical structures were characterized by 1H and 13C nuclear magnetic resonance spectra and elemental analysis. Their thermotropic liquid-crystalline (LC) properties were examined by differential scanning calorimetry, polarizing optical microscopy, and variable temperature X-ray diffraction. Salts with short length alkoxy chains had crystal-to-liquid transitions. Salts of intermediate length alkoxy chains showed both crystal-to-smectic A (SmA) transitions, Tms, and SmA-to-isotropic transitions, Tis. Those with longer length of alkoxy chains had relatively low Tms at which they formed the SmA phases that persisted up to the decomposition at high temperatures. As expected, all of them had excellent thermal stabilities in the temperature range of 330-370 ?C. Their light-emitting properties in methanol were also included.
- Agra-Kooijman, De?a M.,Al-Karawi, Muhammed Kareem M.,Bhowmik, Pradip K.,Chang, Anthony,Chen, Si L.,Cortez, Raymond G.,Dizon, Erenz J.,Fisch, Michael R.,Gutierrez, Bryan,Han, Haesook,Ho, Andy,Killarney, Shane T.,Kim, Jongin,Kumar, Satyendra,Mandal, Hari D.,Mendez, Klarissa,Principe, Ronald Carlo G.,Sharpnack, Lewis
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- Polarization effect in luminescent mesogenic BF2 complexes derived from heterocyclic benzothiazoles
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Two series of benzo(thia)xazoles 1–2 and one series of boron difluoride complexes 2-BF2 derived from benzothiazoles 2 were reported, and their mesomorphic and optical properties were investigated. The crystal and molecular structures of compound 2 and 2-BF2 (all n = 8) were determined by means of X?ray structural analysis, and both crystallize in the triclinic P-1 and monoclinic P21/c. The geometry at boron center is perfectly tetrahedral, and the overall molecular shapes are considered as rod?shape. Both benzo(thia)xazoles 1 and 2 exhibited N or/and SmC phase, and boron complexes 2-BF2 formed N or/and SmC phase. Benzothiazoles 2 showed a much wider temperature range of mesophase than those of benzoxazoles 1, which were attributed to the better polarization by sulfur atom incorporated. Boron complexes 2-BF2 (n = 10, 12) emitted a yellow?to?green emission at λmax = 569–571 nm in CH2Cl2. This is the first mesogenic BF2 complexes derived from benzothiazoles.
- Hsu, Yuan?Chun,Wang, Chun?Yang,Hsiao, Pei?Chi,Cai, Yi-Hong,Lee, Gene?Hsiang,Lai, Chung K.
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- Chiral polymorphism in new imine based rod-like liquid crystals
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New imine based rod-like compounds, composed of three-benzene-ring molecular core linked with azomethine as well as ester groups and terminated with (S)-3,7-dimethyloctyloxy chiral unit at one side have been synthesized. The other terminal position has been varied by using n-octyloxy/decyloxy/dodecyloxy groups to reveal chain length effect on mesophase behavior. The liquid crystalline properties of the new compounds have been investigated by polarizing optical microscopy, differential scanning calorimetry and electro-optic studies. The novel chiral calamitics derived from Schiff base or salicylaldimine-core show a chiral polymorphism comprising of blue phase and chiral nematic as well as smectics such as chiral tilted smectic and unidentified smectic mesophase.
- ?a?lar, Fatma P?nar,Akda?-K?l??, Huriye,Eran, Belk?z Bilgin,Ocak, Hale
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- Flexible π-Conjugated 2,5-Diarylamino-Terephthalates: A New Class of Mechanochromic Luminophores with Tunable Aggregation States
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The generation of different thermodynamically (meta)stable states is crucial for the development of smart solid-state luminescent materials. However, the design of luminophores with tunable aggregation states is remaining a grand challenge. Herein, we present a family of mechanochromic luminophores with tunable metastable states, based on the dynamically controllable π–π stacking of the flexible π-conjugated structure of 2,5-diarylamino-terephthalates in the solid state. The experimental data revealed that both the kinetically controlled metastable state and thermodynamic controlled stable state can be generated via tuning the intermolecular interactions such as π–π stacking and hydrogen bonds. As a result, the highly sensitive mechano-stimuli response of these luminophores was successfully achieved.
- Liu, Zhipeng,Liu, Yi,Qi, Fen,Yan, Hui,Jiang, Zhiyong,Chen, Yuncong
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p. 14963 - 14968
(2020/10/20)
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- 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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- Photoresponsive behavior of hydrophilic/hydrophobic-based novel azobenzene mesogens: Synthesis, characterization and their application in optical storage devices
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Three series of alkoxy chain-bearing azobenzene-derived quaternary ammonium iodides with an alkoxy chain at one end, namely N,N-diethanol-6-(4-((4′-alkyloxyphenyl)diazenyl)phenoxy)hexan-1-ammonium iodides, N-ethyl-N-ethanol-6-(4-((4′-alkyloxyphenyl)diazenyl)phenoxy)hexan-1-ammonium iodides and N,N-diethyl-6-(4-((4′-alkyloxyphenyl)diazenyl)phenoxy)hexan-1-ammonium iodides were synthesized and characterized. Their mesomorphic and photoswitching properties were examined via polarising optical microscopy (POM), differential scanning calorimetry (DSC) and UV-vis spectrophotometry. The liquid crystalline tilted schlieren texture of smectic C, non-tilted natural focal conic texture of smectic A and smectic B phases were observed in the N,N-diethanol- and N-ethyl-N-ethanol-bearing ammonium group substituted at the terminal via the alkoxy chain of the azo moiety. In these azo moieties, the equilibrium time for trans-cis isomerization was about 1 min and cis-trans isomerization occurred at around 590 min, which had the highest alkoxy chain and no hydroxyl group on their head group. The absence of a hydroxyl group on the terminal head group resulted in slow thermal back relaxation, whereas the hydroxyl group-bearing head group showed fast thermal back relaxation. These results suggest that the influence of the substituent on the cationic ammonium head group and alkoxy chain length on the photoisomerization of the azo compounds is vital for optical storage devices. Furthermore, the device fabricated using these materials demonstrated that they are excellent candidates for optical image storage applications.
- Sunil,Yam, Wan Sinn,Hegde, Gurumurthy
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p. 40588 - 40606
(2019/12/25)
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- Structurally simple trimesic amides as highly selective anion channels
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Trimesic amide molecules, which contain simple alkyl chains in their periphery, exhibit interesting anion-transport functions. The most active and highly selective channel TA12 efficiently transports ClO4? anions across membranes, with other anions conducted in the order of I? > NO3? > Br? > Cl?.
- Yuan, Lin,Shen, Jie,Ye, Ruijuan,Chen, Feng,Zeng, Huaqiang
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p. 4797 - 4800
(2019/05/02)
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- Reversible Formation of a Light-Responsive Catalyst by Utilizing Intermolecular Cooperative Effects
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A photoresponsive system where structure formation is coupled to catalytic activity is presented. The observed catalytic activity is reliant on intermolecular cooperative effects that are present when amphiphiles assemble into vesicular structures. Photoresponsive units within the amphiphilic pre-catalysts allow for switching between assembled and disassembled states, thereby modulating the catalytic activity. The ability to reversibly form cooperative catalysts within a dynamic self-assembled system represents a conceptually new tool for the design of complex artificial systems in water.
- Ren, Chloe Z.-J.,Solís Mu?ana, Pablo,Dupont, Julien,Zhou, Silvia Siru,Chen, Jack L.-Y.
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p. 15254 - 15258
(2019/10/22)
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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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p. 15044 - 15051
(2018/09/29)
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- Luminescent mesogenic borondifluoride complexes with the Schiff bases containing salicylideneamines and β-enaminoketones core systems
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Three new families of borondifluoride complexes 1a–c derived from salicylideneamines 2a and β-enaminoketonates 2b–c were reported, and their mesomorphic and optical properties were also investigated. One single crystal and molecular structure of nonmesogenic BF2 complex 1c (n = 10) was resolved and the geometry of the central boron atom was tetrahedron. A larger dihedral angle of 81.3° between the two phenyl rings observed in crystal lattice was attributed to the lack of liquid crystallinity. Boron complexes 1a formed monotropic SmA phases, while boron complexes 1b exhibited enantiotropic SmC mesophases. The optical property of the boron complexes was dependent on their molecular structures, and they emitted a blue–to–green emission at λmax = 476–541 nm in the solution and 488–550 nm in the solid state. This is the first group of mesogenic BF2 complexes with the Schiff bases derived from respective salicylideneamines and β-enaminoketones.
- Lei, Zih-Yang,Lee, Gene-Hsiang,Lai, Chung K.
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- Supramolecular Electropolymerization
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Gaining control over supramolecular polymerization mechanisms is of high fundamental interest to understand self-assembly and self-organization processes at the nanoscale. It is also expected to significantly impact the design and improve the efficiency of advanced materials and devices. Up to now, supramolecular polymerization has been shown to take place from unimers in solution, mainly by variations of temperature or of concentration. Reported here is that supramolecular nucleation-growth of triarylamine monomers can be triggered by electrochemistry in various solvents. The involved mechanism offers new opportunities to precisely address in space and time the nucleation of supramolecular polymers at an electrode. To illustrate the potential of this methodology, supramolecular nanowires are grown an oriented over several tens of micrometers between different types of commercially available electrodes submitted to a single DC electric field, reaching a precision unprecedented in the literature.
- Ellis, Thomas K.,Galerne, Melodie,Armao, Joseph J.,Osypenko, Artem,Martel, David,Maaloum, Mounir,Fuks, Gad,Gavat, Odile,Moulin, Emilie,Giuseppone, Nicolas
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p. 15749 - 15753
(2018/11/10)
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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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- Benzene ring containing cationic gemini surfactants: Synthesis, surface properties and antibacterial activity
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New quaternary ammonium gemini surfactants of the general formula CnH2n?+?1-Ph-NHCOCH2N+(CH3)2-(CH2)s-N+(CH3)2CH2CONH-Ph-CnH2n?+?1 (with n?=?8, 10, 12, 14, 16 and s?=?2, 4, 6) have been synthesized by an efficient synthetic pathway based on the quaternization of N,N,N′,N′-tetramethylalkylenediamine with 2-bromo-N-(4-(alkyloxy) phenyl) acetamides. Their surface properties were investigated by surface tension, electrical conductivity and dynamic light scattering (DLS) measurements. The study shows that the incorporation of a benzene ring in the hydrophobic tail prompts micelle formation which leads to a smaller cmc values in the range of 0.21–0.009?mM compared to analogous geminis bearing alkyl hydrophobic chains. The length of the spacer and the hydrophobic chain has a pronounced effect on the aggregation behavior of surfactants molecules. This was confirmed by the average surfaces occupied by these molecules at the water–air interface calculated from the Gibbs equation. The size of the aggregates was measured by employing dynamic light scattering technique. The antimicrobial activity of investigated surfactants was evaluated against three microorganisms: Staphylococcus aureus, Escherichia coli and Candida albicans.
- Taleb, Khadidja,Mohamed-Benkada, Mustapha,Benhamed, Nadjia,Saidi-Besbes, Salima,Grohens, Yves,Derdour, Aicha
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- Mesogenic heterocycles derived from quinoxaline Schiff Bases
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Three new series of heterocyclic quinoxaline Schiff Bases 1–2 were prepared, characterized and their mesomorphic properties were investigated. These compounds 1 and 2 are in fact geometric isomers in which an imine moiety (e.g., [sbnd]C[dbnd]N) is inversely incorporated into quinoxaline, leading to an opposite local dipole. Two single crystallographic structures 1 (m=8, n=8) and 2a (m=12, n=8) were determined by X-ray crystallographic analysis in order to understand the effect of mesomorphic properties. Weak H-bonds, CH–π and π–π interactions were found in both crystals, which were attributed to the formation of mesomorphic behavior. Variable temperature FT-IR experiments were performed to confirm the induced H-bonds. All series?of compounds 1–2 exhibited N/SmC or SmC phases, which were identified by optical microscope and confirmed by powder X-ray diffraction experiments. Compounds 2a have a slightly wider range of mesophase temperatures than that of compounds 1 and 2b.
- Kuo, Hsiu-Ming,Ko, Wan-Ping,Hsu, Yu-Te,Lee, Gene-Hsiang,Lai, Chung K.
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p. 6321 - 6333
(2016/09/23)
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- Dual photo-functionalized amphiphile for photo-reversible liquid crystal alignments
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Without the conventional polymer-based liquid crystal (LC) alignment process, a newly synthesized dual photo-functionalized amphiphile (abbreviated as ADMA1) was successfully applied as a robust photo-reversible LC alignment layer by self-assembly and photo-polymerization. The LC alignment layer constructed by directly adding dual photo-functionalized amphiphiles into LC media significantly cuts the manufacturing cost as well as opens new doors for the fabrication of novel electro-optical devices.
- Kim, Dae-Yoon,Lee, Sang-A.,Park, Minwook,Jeong, Kwang-Un
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p. 545 - 548
(2015/02/19)
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- Photoresponsive ionic liquid crystals based on azobenzene guanidinium salts
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The use of non-ionic LC phases as anisotropic matrices for E/Z-isomerization of azo-guest molecules is often restricted due to limited solubilities and demixing effects. In this study we therefore employed an ionic liquid crystal (ILC) matrix to follow the photo-induced E/Z-isomerization of ionic mesogenic azobenzene guanidinium guests. The latter were prepared from 4-hydroxy-4′-(octyloxy)azobenzene, which was first treated with N-(bromoalkyl)phthalimides to introduce the spacer with varying chain length. Removal of phthalimide and final reaction with a formamidinium salt linked the ionic head group to the photoisomerizable azobenzene unit. Investigation of the mesomorphic behaviour revealed for all azobenzene ILCs smectic A mesophases with high translational order parameters and partial bilayers, as could be stated by layer spacing d. Similar packing behaviour was found for the solid state by X-ray crystal structure analysis. E/Z-isomerization of azobenzene ILCs which were completely miscible with the ionic LC phase of C12MIM-Br as anisotropic host was induced by irradiation with UV light and the reisomerization observed by time-resolved UV-Vis spectroscopy. For comparison, water was used as isotropic host. Z/E-reisomerization activation energies exhibited similar values of 97-100 kJ mol-1 irrespective of spacer lengths and the type of host. The results demonstrate that a proper match of steric requirements of host and guest as well as layer spacings are needed for a decreased activation energy. This journal is
- Wuckert, Eugen,Harjung, Marc D.,Kapernaum, Nadia,Mueller, Carsten,Frey, Wolfgang,Baro, Angelika,Giesselmann, Frank,Laschat, Sabine
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p. 8382 - 8392
(2015/04/14)
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- An azobenzene-based photochromic liquid crystalline amphiphile for a remote-controllable light shutter
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By considering intramolecular conformations and intermolecular interactions, an azobenzene-based photochromic liquid crystalline amphiphile is synthesized for demonstrating a remote-controllable light shutter by the photo-induced isothermal phase transition between the highly ordered crystal phase and the isotropic liquid phase.
- Kim, Dae-Yoon,Lee, Sang-A,Kim, Huisu,Min Kim, Soo,Kim, Namil,Jeong, Kwang-Un
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p. 11080 - 11083
(2015/07/02)
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- Novel organogelators based on pyrazine-2,5-dicarboxylic acid derivatives and their mesomorphic behaviors
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A series of new low molecular organogelators (LMOGs) with thermotropic mesophase were synthesized via the reaction of 3,6-dimethyl-pyrazine-2,5- dicarboxylic acid with p-alkoxyl anilines. These compounds readily formed stable gels in a variety of organic solvents and their self-assembly behavior, structure-property relationship were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), 1H nuclear magnetic resonance (1H NMR), Fourier transform infrared spectroscopy (FTIR) and ultra-violet-visible spectroscopy (UV). The results showed a combination of intra-hydrogen bonding, π-π stacking and van der Waals interaction resulted in the aggregation of the organogelators to form three-dimension fibrous networks. The gels formed were multi-responsive to environmental stimuli, such as temperature, fluorinion, and shear stress. More importantly, all the organogelators exhibited thermotropic hexagonal column mesophase as revealed by differential scanning calorimetry (DSC), polarized optical microscopy (POM), and variable temperature XRD studies. A control compound was synthesized and its gelling ability was also checked.
- Huang, Yao-Dong,Tu, Wei,Yuan, Yu-Qin,Fan, Dong-Li
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p. 1274 - 1282
(2014/02/14)
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- Thermal- and photo-induced phase-transition behaviors of a tapered dendritic liquid crystal with photochromic azobenzene mesogens and a bicyclic chiral center
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A ribbon-shaped chiral liquid crystalline (LC) dendrimer with photochromic azobenzene mesogens and an isosorbide chiral center (abbreviated as AZ 3DLC) was successfully synthesized and its major phase transitions were studied by using differential scanning calorimetry (DSC) and linear polarized optical microscopy (POM). Its ordered structures at different temperatures were further identified through structure-sensitive diffraction techniques. Based on the experimental results, it was found that the AZ 3DLC molecule exhibited the low-ordered chiral smectic (Sm*) LC phase with 6.31nm periodicity at a high-temperature phase region. AZ 3DLC showed the reversible photoisomerization in both organic solvents and nematic (N) LC media. As a chiral-inducing agent, it exhibited a good solubility, a high helical-twisting power, and a large change in the helical-twisting power due to its photochemical isomerization in the commercially available N LC hosts. Therefore, we were able to reversibly "remote-control" the colors in the whole visible region by finely tuning the helical pitch of the spontaneously formed helical superstructures. Remote-controlled color: A ribbon-shaped chiral dendritic liquid crystal was newly synthesized, and its thermal and photo-induced phase behaviors were investigated with the combined techniques of the thermal, microscopic, and scattering methods (see figure).
- Kim, Dae-Yoon,Lee, Sang-A,Choi, Yu-Jin,Hwang, Seok-Ho,Kuo, Shiao-Wei,Nah, Changwoon,Lee, Myong-Hoon,Jeong, Kwang-Un
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p. 5689 - 5695
(2014/05/20)
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- Phototunable liquid-crystalline phases made of nanoparticles
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The properties of liquid-crystalline (LC) hybrid systems made of inorganic nanoparticles grafted with photosensitive azo compounds are presented. For materials with a large density of azo ligands at the surface, the LC structure can be reversibly melted by UV light, and the return to the LC state does not require the absorption of visible light. For systems with a lower density of azo ligands, UV light causes shortening of the distance between metal sublayers in the lamellar phase. Interestingly, the azo derivatives attached to the nanoparticle surface show very different kinetics of cis/trans conformational change as compared to the free molecules. The cis form of free ligands in solution is stable for days, whereas the isomerization of molecules attached to the nanoparticle surface to the trans form takes only a few minutes. Apparently, owing to the crowded environment, azo ligands immobilized at a metal surface behave as they would in the condensed state.
- Zep, Anna,Wojcik, Michal M.,Lewandowski, Wiktor,Sitkowska, Kaja,Prominski, Aleksander,Mieczkowski, Joef,Pociecha, Damian,Gorecka, Ewa
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p. 13725 - 13728
(2015/04/16)
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- Structure-property correlation of benzoyl thiourea derivatives as organogelators
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A series of N-benzoyl-N′-aryl thiourea derivatives (1-4) can form stable gels from a variety of organic solvents ranging from protic to aprotic or polar to apolar at concentrations below 5 mg/mL. The gelation properties and structures of the resulting gels were investigated by 1H-NMR, FTIR, UV-vis, SEM, and XRD. The gels were anion-responsive and the driving forces for its formation were the hydrogen bonding and van der Waals interaction. The SEM images of the xerogels prepared from the organogels formed in acetonitrile, cyclohexane and acetone showed a network of elongated fibers. The results of XRD suggested that the dry gels had a layer structure.
- Huang, Yao-Dong,Dong, Xue-Lin,Zhang, Li-Li,Chai, Wei,Chang, Ji-Young
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- Rational design, syntheses, characterization and solution behavior of amphiphilic azobenzene-containing linear-dendritic block copolymers
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In this paper, based on the synthesis of precursor linear-dendritic block copolymers (LDBCs) with a linear poly(ethylene glycol) (PEG) block of molecular weight around 2000 and dendritic polyamidoamine (PAMAM) segments of generation G0 to G3, a series of azobenzene-containing amphiphilic LDBCs mPEG-dendr[PAMAM-(AZO)n] (n = 2, 4, 8, 16) have been successfully prepared in moderate yields 45-60%, through complete Michael addition between the peripheral amine groups of dendritic segment and the reactive azobenzene acrylate mesogen units bearing octyloxy tails and flexible decylmethylene spacers. The purified copolymers have been characterized and confirmed by NMR, FT-IR, MALDI-TOF MS, and GPC showing narrow molecular weight distribution in the range 1.09-1.20. A generation-dependent polymeric micellar aggregation behavior of thus obtained amphiphilic LDBCs from nanofibers of uniform diameter around 20 nm to nanospheres/oval sheets, vesicles, and porous large compound micelles (LCMs) of micrometer size has been demonstrated in selective solvent mixture of dioxane/water. Furthermore, photoisomerization transformation of these azobenzene-containing LDBCs and their kinetics of reversible trans-cis-trans photochemical transitions in THF solution have also been investigated, the measured trans-cis photoisomerization rate constant 0.0240 s-1 for G3 copolymer is twice of the 0.0127 s-1 determined for the precursor azobenzene compound, manifesting a kind of promising photoresponsive copolymer materials.
- Shi, Zehua,Lu, Huanjun,Chen, Zhaocong,Cheng, Rongshi,Chen, Dongzhong
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p. 359 - 369
(2012/05/05)
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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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- 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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- 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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- Supramolecularly engineered perylene bisimide assemblies exhibiting thermal transition from columnar to multilamellar structures
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Perylene 3,4:9,10-tetracarboxylic acid bisimide (PBI) was functionalized with ditopic cyanuric acid to organize it into complex columnar architectures through the formation of hydrogen-bonded supermacrocycles (rosette) by complexing with ditopic melamines possessing solubilizing alkoxyphenyl substituents. The aggregation study in solution using UV-vis and NMR spectroscopies showed the formation of extended aggregates through hydrogen-bonding and π-π stacking interactions. The cylindrical fibrillar nanostructures were visualized by microscopic techniques (AFM, TEM), and the formation of lyotropic mesophase was confirmed by polarized optical microscopy and SEM. X-ray diffraction study revealed that a well-defined hexagonal columnar (Colh) structure was formed by solution-casting of fibrillar assemblies. All of these results are consistent with the formation of hydrogen-bonded PBI rosettes that spontaneously organize into the Col h structure. Upon heating the Colh structure in the bulk state, a structural transition to a highly ordered lamellar (Lam) structure was observed by variable-temperature X-ray diffraction, differential scanning calorimetry, and AFM studies. IR study showed that the rearrangement of the hydrogen-bonding motifs occurs during the structural transition. These results suggest that such a striking structural transition is aided by the reorganization in the lowest level of self-organization, i.e., the rearrangement of hydrogen-bonded motifs from rosette to linear tape. A remarkable increase in the transient photoconductivity was observed by the flash-photolysis time-resolved microwave conductivity (FP-TRMC) measurements upon converting the Colh structure to the Lam structure. Transient absorption spectroscopy revealed that electron transfer from electron-donating alkoxyphenyl groups of melamine components to electron-deficient PBI moieties takes place, resulting in a higher probability of charge carrier generation in the Lam structure compared to the Colh structure.
- Yagai, Shiki,Usui, Mari,Seki, Tomohiro,Murayama, Haruno,Kikkawa, Yoshihiro,Uemura, Shinobu,Karatsu, Takashi,Kitamura, Akihide,Asano, Atsushi,Seki, Shu
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p. 7983 - 7994
(2012/06/30)
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- Influences of hydrogen bonding and peripheral chain length on mesophase structures of mesogen-jacketed liquid crystalline polymers with amide side-chain linkages
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A series of mesogen-jacketed liquid crystalline polymers, poly{2,5-bis[(4-alkoxyphenyl)aminocarbonyl]styrene} (P-Cm, where m is the number of carbon atoms in the alkoxy groups, and m = 1, 4, 8, 12), with an amide core and flexible tails of varying lengths on the two ends in the side chain were designed and successfully synthesized via conventional radical polymerization. The mesophase structures of these polymers were dependent on the number of carbon atoms in the peripheral chains. Wide-angle X-ray diffraction and polarized light microscopy results revealed that the polymers with m ≥ 4 could form smectic A phases, while a columnar nematic phase could be formed for the polymer with methoxy end groups (P-C1). The hydrogen bonding among the side-chain amide groups might play an important role in forming and stabilizing these liquid crystalline phases, which was suggested by the results from variable-temperature FTIR and 2D IR analyses.
- Cheng, Yan-Hua,Chen, Wen-Ping,Shen, Zhihao,Fan, Xing-He,Zhu, Mei-Fang,Zhou, Qi-Feng
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p. 1429 - 1437
(2011/10/07)
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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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p. 172 - 191
(2012/07/27)
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- PHTHALANILATE COMPOUNDS AND METHODS OF USE
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The invention provides antimicrobial compounds and compositions, and methods of using them. The compounds and compositions include, for example, a compound of any one of Formulas I-X. The invention further provides methods of preparing the compounds, and useful intermediates for their preparation. The compounds can possess highly specific and selective activity, such as antibacterial activity and/or enzymatic inhibitory activity. Accordingly, the compounds and compositions can be used to treat bacterial infections, or to inhibit or kill bacteria, either in vitro or in vivo.
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Page/Page column 54
(2011/04/14)
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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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- Synthesis and evaluation of alkoxy-phenylamides and alkoxy-phenylimidazoles as potent sphingosine-1-phosphate receptor subtype-1 agonists
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In the design of potent and selective sphingosine-1-phosphate receptor agonists, we were able to identify two series of molecules based on phenylamide and phenylimidazole analogs of FTY-720. Several designed molecules in these scaffolds have demonstrated selectivity for S1P receptor subtype 1 versus 3 and excellent in vivo activity in mouse. Two molecules PPI-4621 (4b) and PPI-4691 (10a), demonstrated dose responsive lymphopenia, when administered orally.
- Evindar, Ghotas,Bernier, Sylvie G.,Kavarana, Malcolm J.,Doyle, Elisabeth,Lorusso, Jeanine,Kelley, Michael S.,Halley, Keith,Hutchings, Amy,Wright, Albion D.,Saha, Ashis K.,Hannig, Gerhard,Morgan, Barry A.,Westlin, William F.
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body text
p. 369 - 372
(2011/03/18)
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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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- Liquid crystal imidazolium salts: Towards materials for catalysis and molecular electronics
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1,3-Bis(4-alkyloxyphenyl)-3H-imidazol-1-ium trifluoromethanesulfonates, alkyl = CH3(CH2)n-1, n = 8, 10, 12, 14 and 16, can be derived from the analogous 4-alkyloxyphenylamines. These imidazolium salts exhibit a lamellar liquid-crystal mesophase between 99°C and 191°C. The smectic-A phase was fully characterised by polarising optical microscopy, differential scanning calorimetry and X-ray diffraction. We report also the synthesis, lamellar crystal structure and catalytic activity of the PdII complex of the (deprotonated) carbene form of one of these salts. In addition, we measured the charged carrier mobilities in the mesophase. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
- Suisse, Jean-Moise,Douce, Laurent,Bellemin-Laponnaz, Stephane,Maisse-Francois, Aline,Welter, Richard,Miyake, Yasuo,Shimizu, Yo
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p. 3899 - 3905
(2008/03/14)
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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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- Discotic liquid crystalline hydrazone compounds: Synthesis and mesomorphic properties
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1,3,5-Trisacetoacetamidobenzene with three 1,3-diketo groups was synthesized by the reaction of 1,3,5-triaminobenzene with diketene. Discotic hydrazone compounds were prepared by the diazo coupling reaction between 1,3,5-trisacetoacetamidobenzene and diazonium salts of 4-alkyloxyphenylamines. The compounds existed in hydrazone forms exclusively, being stabilized by the intramolecular hydrogen bonds, and showed discotic nematic or columnar hexagonal mesophases.
- Jeong, Min Ju,Park, Jun Ha,Lee, Changjin,Chang, Ji Young
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p. 2221 - 2224
(2007/10/03)
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- METHODS AND COMPOSITIONS FOR MODULATING SPHINGOSINE-1-PHOSPHATE (S1P) RECEPTOR ACTIVITY
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The present invention relates to compounds which modulate the activity of the SI P1 receptor, the use of these compounds for treating conditions associated with signaling through the S1 P1 receptor, and pharmaceutical compositions comprising these compounds.
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Page/Page column 54
(2010/10/20)
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- A surfactant-encapsulated polyoxometalate complex towards a thermotropic liquid crystal
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A novel surfactant-encapsulated terbium-substituted heteropolyoxotungstate complex [L1]13[Tb(SiW11O39)2] ·30H2O (SEC-1) bearing mesomorphous groups was successfully prepared by the ionic self-assembling route, exhibiting characteristic thermotropic liquid-crystalline behavior. The Royal Society of Chemistry 2005.
- Li, Wen,Bu, Weifeng,Li, Haolong,Wu, Lixin,Li, Min
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p. 3785 - 3787
(2007/10/03)
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- A novel method for creation of free volume in a one-component self-assembled monolayer. Dramatic size effect of para-carborane
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We fabricated the self-assembled monolayers (SAMs) composed of 4-(12-(10-mercaptodecyl)-1,12-dicarba-closo-dodecaborane)-4′-octyloxy azobenzene and 4-(10-mercaptodecyloxy)-4′-octyloxyazobenzene on a gold surface, and performed photoswitching experiments. The SAM including p-carborane exhibited a much higher and more reversible photochemical response in comparison with the SAM in the absence of the p-carborane. This result suggests that the free volume of the azobenzene moiety to change its conformation is increased due to the size effect of the p-carborane.
- Ito, Masateru,Wei, Tian Xin,Chen, Peng-Lei,Akiyama, Haruhisa,Matsumoto, Mutsuyoshi,Tamada, Kaoru,Yamamoto, Yoshinori
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p. 478 - 483
(2007/10/03)
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- Structure-activity studies of ferroelectric and antiferroelectric imine ligands and their palladium(II) complexes. An antiferroelectric metallomesogen
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The synthesis and characterization of the mesomorphic and dielectric properties of new imine-based liquid crystalline compounds that exhibit tilted SmC* phases is reported. The presence of an imino linkage within the mesogenic nucleus of these compounds is significant due to the ability of benzaldimines to coordinate to metals. Complexation to a divalent metal such as Pd(II) has been studied in order to assess the effects of antiparallel dimerization of organic ligands, through metal-coordination, on the appearance of antiferroelectric order in the mesophase. An organometallic palladium(II) complex has been prepared and this shows antiferroelectric behaviour over the whole range of the tilted smectic mesophase. Structure-activity studies have also been carried out by varying structural elements in the composition of the ligands. The changes include the disposition of the linking groups within the mesogenic core, and presence of a lateral hydroxy group.
- De Murillas, Delia Lopez,Pinol, Rafael,Ros, M. Blanca,Serrano, Jose Luis,Sierra, Teresa,De La Fuente, M. Rosario
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p. 1117 - 1127
(2007/10/03)
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- Influence of π-stacking along with hydrogen bonding interactions in the recognition of monocarboxylic acids
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The new receptors 1 and 2 have been designed and synthesized where phenyl and naphthalene rings have been introduced in place of aliphatic chain in receptor 3 to achieve the π-stacking interactions. These receptors show higher association constants with aromatic over aliphatic carboxylic acids compared to receptor 3 which preferably recognizes long chain aliphatic acid.
- Goswami, Shyamaprosad,Ghosh, Kumaresh,Ghosh, Samaresh
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p. 1187 - 1192
(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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- Synthesis and structure of 1,4-diazabutadiene liquid crystals
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Nine 1,4-diazabutadiene compounds, Ar-N=C(R)-C(R)=N-Ar, R=H, Me; Ar= H2n+1CnO-C6H4, 2,4-(H9C4O)(Me)-C6H3 were synthesized and their liquid crystal properties were studied through thermal polarizing microscopy. The X-ray single crystal structure of compound 9 (Ar-N=C(H)-C(H)=N-Ar, Ar=2,4-(Me)(H9C4O)C6H3) was tested. It is a monoclinic crystal system, space group P21/C with the unit cell parameters: a=7.0703(3)A, b=8.674(4)A, c=18.3115(8)A, β =95.392(1)°. V=1114.57(9)A3, z=2, Dc=1.134 Mg/m3, R=0.0490,Rw=0.1237.
- Zhao, Ke-Qing,Hu, Pin,Xu, Hong-Bo
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p. 801 - 808
(2007/10/03)
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- Smectic mesophase properties of dimeric compounds. 2. Distinct formation of smectic structures with antiferroelectric ordering and frustration
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We have prepared two series of dimeric compounds, which comprise the schiff's base mesogen, alkyl spacer with the carbon number of 5 and alkyl or alkoxy tail with the carbon number of m = 4 approx. 16. In these compounds, we observed three types of smectic liquid crystals, the single layer phase with the tail group randomly mixing with the spacer, the bilayer phase in which the segregation of the spacer and tail groups takes place and so two mesogenic layers are included within a repeat unit, the frustrated smectic phase in which the density modulation appears along the layer as well as the layer normal. The bilayer phase was found to be antiferroelectric and the frustrated smectic phase was considered to result from the two dimensional escape from the dipolar interaction. The phase behaviour with m and the structure and properties of each phase will be described in detail.
- Watanabe, Junji,Izumi, Tatuya,Niori, Teruki,Zennyoji, Masahito,Takanishi, Yoichi,Takezoe, Hideo
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- Synthesis of dinuclear complexes of rhenium(I) as potential metallomesogens
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Seven anisotropic diimines and their corresponding dinuclear complexes of rhenium(i) have been synthesized. The crystal and molecular structures of one of the dimines and two of the complexes were determined. In common with related inline ligands which have been synthesized previously, the new diimines were mesomorphic showing smectic C and nematic phases and, in some cases, smectic I and crystal J phases. However, none of the orthometallated, dinuclear complexes showed any liquid crystal phases. The Royal Society of Chemistry 2000.
- Guillevic, Marie-Andree,Light, Mark E.,Coles, Simon J.,Gelbrich, Thomas,Hursthouse, Michael B.,Bruce, Duncan W.
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p. 1437 - 1445
(2007/10/03)
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- Reactivity of mesogenic diacetylenes coupled with phase transitions between crystal and liquid crystal phases
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Among mesogenic diacetylenes, N-[4-(5-hydroxypenta-1,3-diynyl)benzylidene]-4-alkoxyaniline (DA-Cn), in which n is the number of carbon atoms in the alkoxy group, DA-C8 has been found to have four phases divided by three endothermic transition temperatures. The four phases have been assigned to crystal phase I (T CI-CII = 96°C), crystal phase G (TCII-CG = 115°C) AND nematic phase . (TCG-N = 123°C), based on DCS measurements and observation under a microscope. The crystal structure of DA-C8 in phase I has been determined. Crystal data are triclinic, space group P1, a = 14.580(3), b = 17.451(4), c = 10.219(3) A, a = 93.40(2), β = 103.83(2), γ = 116.85(3)° and Z = 4. Four molecules in a unit cell are hydrogen-bonded to each other at the hydroxymethyl groups and/or the imino-nitrogens of the benzylideneaniline moieties to form a checker-like structure. The phase transitions have been monitored by X-ray powder diffraction measurements. The checker-like structure in crystal I is transformed to a layered structure in crystal phase II and in crystal phase G. The structural transformation may be coupled with a change in the hydrogen-bonding scheme. Whereas crystal phase I is inactive towards the solid state polymerization, crystal phase II polymerizes with a long induction time of 50 h at 110°C. However, the induction time of the polymerization is shortened greatly in crystal phase G, and the polymerization in the nematic phase proceeds smoothly with almost no induction time. The results are interpreted in terms of the relative orientation of diacetylene molecules in each phase.
- Okuno, Tunehisa,Izuoka, Akira,Ito, Tomoyoshi,Kubo, Sachiyo,Sugawara, Tadashi,Sato, Naoki,Sugawara, Yoko
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p. 889 - 895
(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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