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Journal ArticleDOI

A simple and inexpensive capillary furnace for variable‐temperature X‐ray diffraction

01 Feb 2008-Journal of Applied Crystallography (International Union of Crystallography)-Vol. 41, Iss: 1, pp 214-216
TL;DR: In this article, an inexpensive capillary furnace has been developed for variable-temperature X-ray diffraction in transmission geometry of air-stable liquid crystals and other materials, which offers temperature control with fluctuations of less than ± 1
Abstract: An inexpensive capillary furnace has been developed for variable-temperature X-ray diffraction in transmission geometry of air-stable liquid crystals and other materials. It offers temperature control with fluctuations of less than ±1 K in the range of interest for these samples, from room temperature to near 573 K. Phases can be accessed through heating or cooling with no significant overshooting of the target temperature. The furnace is designed to fit on a classical goniometer, and can be controlled by any standard temperature controller. The simple design of this furnace means that it is both inexpensive to build and easy to operate.
Citations
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Journal ArticleDOI
TL;DR: Contrary to expectations, the presence of a carboxylic acid group on the side of the core does not appear to lead to the formation of dimeric structures in the liquid crystalline phase, although the columnar structures appear to be stabilized by intermolecular hydrogen bonding along the columns.
Abstract: The effects of functional group position on the phase behavior of discotic mesogens was examined for a series of dibenzophenazine derivatives bearing a carboxylic acid, methyl carboxylate, or nitro group. In all cases, changing the position of the group from the "top" to the "side" of the aromatic core led to dramatic differences in the phase behavior, both in terms of the stability of the liquid crystalline phases as well as the types of mesophases formed. For the non-hydrogen bonding ester and nitro derivatives, moving the substituent to the side of the core led to a lowering of the clearing temperatures or loss of liquid crystallinity. Carboxylic acid derivatives exhibit broad mesophases irrespective of the position of the acid group, but mesogens bearing this group on the side of the core exclusively form Col(h) phases, whereas those with an acid group on the top of the core exhibit more varied mesomorphism, with the formation of Col(h), Col(r), and nematic phases. Contrary to expectations, the presence of a carboxylic acid group on the side of the core does not appear to lead to the formation of dimeric structures in the liquid crystalline phase, although the columnar structures appear to be stabilized by intermolecular hydrogen bonding along the columns. These derivatives also form pi-stacked dimers in solution; the structure of these dimers are consistent with the proposed structure of the columnar phases.

85 citations

Journal ArticleDOI
TL;DR: A dibenzophenazine discotic dimer is found to adopt a folded conformation in solution, which allows the dimer to assemble into a columnar liquid crystal phase, despite its short linking group.
Abstract: We report the synthesis and properties of a dibenzophenazine discotic dimer, which was found to adopt a folded conformation in solution. This stable π-stacked structure persists at elevated temperatures and in all solvents examined. Folding allows the dimer to assemble into a columnar liquid crystal phase, despite its short linking group.

16 citations

Journal ArticleDOI
TL;DR: A series of novel β-CD derivatives capable of forming hydrogen bonding networks of different strengths have been synthesized to probe the role of the hydrogen bonding network in the formation of self-assembled mesophases.
Abstract: A series of novel amphiphilic β-CD derivatives capable of forming hydrogen bonding networks of different strengths have been synthesized to probe the role of the hydrogen bonding network in the formation of self-assembled mesophases. Using differential scanning calorimetry (DSC), cross-polarized optical microscopy (POM) and X-ray diffractometry, two compounds were found to exhibit smectic mesophases. These correlated well with their abilities to form a hydrogen bonding network with sufficient strength to self-assemble. It was also observed that modifying the secondary face to interfere with the hydrogen bonding network significantly affects the Tc of a CD amphiphiles while the Tm temperature was not greatly affected.

16 citations

Journal ArticleDOI
TL;DR: In this article, a thermotropic liquid crystalline (LC) cyclodextrin (CD) composites of self-assembling and environment-friendly amphiphilic β-CDs with lithium bistrifluoromethanesulfonimidate (LiTFSI) is reported.
Abstract: The first family of lithium-ion electrolytes based on thermotropic liquid crystalline (LC) cyclodextrin (CD) is reported. The new electrolytes consist of composites of self-assembling and environment-friendly amphiphilic β-CDs with lithium bistrifluoromethanesulfonimidate (LiTFSI). The unique geometry of the CD scaffold allows for efficient control of the amphiphilicity of the molecule through chemical derivatizations. The introduction of non-polar alkyl chains at the primary face of CD and multiple short and polar nitrile-terminated tetraethylene glycol chains at the other face provides a new class of LC materials capable of self-organization into homeotropically-aligned smectic mesophases, which retain long-range order over a wide temperature window. The assembly of numerous ethoxy groups at the secondary face of CD serves as an elegant pre-organization of the ion-chelating groups to form two-dimensional ion-conducting pathways, facilitating the directional motion of metal ions. Studies of several LC composites with LiTFSI have revealed promising thermal stability and ionic conductivity. Solid-state NMR studies have uncovered an activation energy of 0.14 eV for lithium diffusion, while cyclic voltammetry confirmed the composites remain electrochemically stable over a potential range of up to ∼3 V versus Li/Li+. These results demonstrate the great potential of this new class of organic electrolytes for different metal ions.

14 citations

Journal ArticleDOI
TL;DR: In this article, the synthesis and comparative studies of a synthetic liquid crystal dimer and two of its monomer analogues are presented, where a flexible scaffold consisting of a hybrid of non-polar hydrophobic chain and polar tetraethylene glycol appended to the cholesteryl mesogens.
Abstract: Oligo/polymerisation of known mesogens constitutes a highly efficient strategy in liquid crystal research due to its potential to generate novel liquid crystal materials with intriguing mesomorphic properties. Here we report the synthesis and comparative studies of a synthetic liquid crystal dimer and two of its monomer analogues. By incorporating cholesterol as the mesogenic group, we designed a flexible scaffold consisting of a hybrid of non-polar hydrophobic chain and polar tetraethylene glycol appended to the cholesteryl mesogens. Detailed studies showed that the two classes of mesogens exhibit the same type of liquid crystal phases with similar dimensions but their transition temperatures varied which can be effectively rationalised by the particular chemical functionalities present in each class of materials.

13 citations


Additional excerpts

  • ...using an in-house built temperature controller [58]....

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References
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Journal ArticleDOI
TL;DR: This Review will focus on the major classes of columnar mesogens rather than presenting a library of columner liquid crystals, and emphasis will be given to efficient synthetic procedures, and relevant mesomorphic and physical properties.
Abstract: Most associate liquid crystals with their everyday use in laptop computers, mobile phones, digital cameras, and other electronic devices. However, in contrast to their rodlike (calamitic) counterparts, first described in 1907 by Vorlander, disklike (discotic, columnar) liquid crystals, which were discovered in 1977 by Chandrasekhar et al., offer further applications as a result of their orientation in the columnar mesophase, making them ideal candidates for molecular wires in various optical and electronic devices such as photocopiers, laser printers, photovoltaic cells, light-emitting diodes, field-effect transistors, and holographic data storage. Beginning with an overview of the various mesophases and characterization methods, this Review will focus on the major classes of columnar mesogens rather than presenting a library of columnar liquid crystals. Emphasis will be given to efficient synthetic procedures, and relevant mesomorphic and physical properties. Finally, some applications and perspectives in materials science and molecular electronics will be discussed.

1,056 citations


"A simple and inexpensive capillary ..." refers background in this paper

  • ...Liquid crystals have generated much interest, both as prime examples of self-assembly and as candidates for numerous applications such as displays, light-emitting devices and organic field effect transistors (Hirschmann & Reiffenrath, 1998; Laschat et al., 2007)....

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Journal ArticleDOI
TL;DR: The observed trends can be rationalized in terms of the strength of pi-pi interactions between aromatic cores in the liquid crystalline phases and suggest that both electrostatic interactions and dispersion forces play important roles in the self-assembly of these materials.
Abstract: A series of disc-shaped molecules were prepared by the condensation of 1,2-diamines with 2,3,6,7-tetrakis(hexyloxy)phenanthrene-9,10-dione to investigate the relationship between changes in molecular structure and the self-assembly of columnar liquid crystalline phases. A comparison of compounds with different core sizes indicated that molecules with larger aromatic cores had a greater propensity to form columnar phases, as did compounds substituted with electron-withdrawing groups. In contrast, molecules with electron-donating substituents were nonmesogenic. The clearing temperature of columnar phases increased linearly with the electron-withdrawing ability of the substituents, as quantified by Hammett σ-values. The observed trends can be rationalized in terms of the strength of π−π interactions between aromatic cores in the liquid crystalline phases and suggest that both electrostatic interactions and dispersion forces play important roles in the self-assembly of these materials.

153 citations


"A simple and inexpensive capillary ..." refers background in this paper

  • ...Previous investigations had indicated that this mesogen exhibits a monotropic liquid-crystalline phase (only accessible on cooling), and we had been unable to obtain an X-ray diffraction pattern of this phase (Foster et al., 2006)....

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Journal ArticleDOI
TL;DR: In this paper, the effect of hydrogen bonding on the phase behaviour of discotic mesogens was investigated with a series of dibenzophenazine carboxylic acids and their methyl ester analogues.
Abstract: The effect of hydrogen bonding on the phase behaviour of discotic mesogens was investigated with a series of dibenzophenazine carboxylic acids and their methyl ester analogues. The esters exhibit only columnar hexagonal phases, while the acids form columnar hexagonal, columnar rectangular and nematic mesophases. The acids have much higher transition temperatures and supercool to room temperature while maintaining the liquid crystalline ordering. These differences could be explained by the ability of the acids to form hydrogen-bonded dimers, which may also be regarded as supramolecular elliptically-shaped mesogens.

71 citations


"A simple and inexpensive capillary ..." refers methods in this paper

  • ...The capillary furnace was then used to measure the diffraction pattern of four previously studied liquid-crystalline samples: molecules 1a, 1b, 2a and 2b (Foster et al., 2005; Lavigueur et al., 2007) shown in Fig....

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Journal ArticleDOI
TL;DR: In this article, a cylindrical symmetry X-ray microtomography furnace has been designed and constructed to study in situ the structural evolution of materials by using synchrotron Xray micro-tomography, compatible with the required 180° rotation, small dimensions and low absorption.
Abstract: A furnace covering the temperature range from 298 to 1300 K has been designed and constructed to study in situ the structural evolution of materials by using synchrotron X-ray microtomography. The furnace has cylindrical symmetry, compatible with the required 180° rotation, small dimensions and low absorption. It can also be used for other scattering methods, such as diffraction.

40 citations


"A simple and inexpensive capillary ..." refers background in this paper

  • ...In some cases, the high power consumption required to reach such high temperatures meant that a water cooling system was also necessary (Bellet et al., 2003; Muller et al., 1997)....

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  • ...Many of the previously reported furnaces also provide the possibility of operating under controlled atmosphere (Bellet et al., 2003; Puig-Molina et al., 2001; Valdrè, 1999) or offer very high temperature stability (better than 0.05 K) (Bellet et al., 2003)....

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  • ...Many heaters have been described in the past few years, most of which have focused on very high temperature applications, typically reaching temperatures between 1273 and 2273 K (Bellet et al., 2003; Muller et al., 1997; PuigMolina et al., 2001; Valdrè, 1999)....

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Journal ArticleDOI
Abstract: Discotic mesogens featuring a pyridine ring were synthesized, and were found either to form ordered hexagonal columnar liquid crystalline phases or melt directly from a crystal to an isotropic liquid, depending on the position of the pyridyl nitrogen atom. Binary mixtures of the mesogenic pyridine derivatives with a similar discotic mesogen having a carboxylic acid group resulted in the formation of modular elliptical complexes through hydrogen bonding. The binary mixtures were found to exhibit ordered hexagonal columnar or ordered rectangular columnar and nematic mesophases, depending on the length of the alkyl chains, and displayed dramatically different properties from their constituent components. Binary mixtures of the non‐mesogenic pyridine derivatives with carboxylic acid‐functionalized discotic mesogens did not result in the formation of hydrogen‐bonded complexes.

19 citations


"A simple and inexpensive capillary ..." refers methods in this paper

  • ...The capillary furnace was then used to measure the diffraction pattern of four previously studied liquid-crystalline samples: molecules 1a, 1b, 2a and 2b (Foster et al., 2005; Lavigueur et al., 2007) shown in Fig....

    [...]