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Showing papers in "Molecular Crystals and Liquid Crystals in 2003"


Journal ArticleDOI
TL;DR: The application of the pulse-radiolysis time-resolved microwave conductivity technique, "PR-TRMC", to the determination of intracolumnar charge carrier mobilities within mesomorphic discotic materials is described in this article.
Abstract: The application of the pulse-radiolysis time-resolved microwave conductivity technique, "PR-TRMC", to the determination of intracolumnar charge carrier mobilities within mesomorphic discotic materials is described. A review is given of the mobility values obtained for the large variety of materials which have been studied since the first results were reported in 1989. This includes peripherally substituted derivatives of triphenylene, phthalocyanine, porphyrin and hexabenzo-coronene. The influences of temperature, morphology and variations in the primary molecular structure are demonstrated and discussed. Both the mesomorphic and conductive properties are shown to be dramatically influenced by subtle changes in the peripheral alkyl chain structure or the core-to-chain coupling element, in addition to changes in the nature of the aromatic core itself. Mobilities as high as 1 cm 2 /Vs are found in crystalline solids, and well in excess of 0.1 cm 2 /Vs in columnar, liquid crystalline phases; values which app...

108 citations


Journal ArticleDOI
TL;DR: In this article, a review of discotic liquid crystalline semiconductors is presented, and it is shown that some of them show very fast carrier mobilities, such as bis[octakis(alkylthio)phthalocyaninato]lutetium(III), which is the fastest in liquid crystals at the present time, so far as we know.
Abstract: Our works on discotic liquid crystalline semiconductors are reviewed. Some of them show very fast carrier mobilities. Novel sandwich rare earth metal complex, bis[octakis(alkylthio)phthalocyaninato]lutetium(III), shows a mobility of 0.71 cm 2 /Vs, which is the fastest in liquid crystals at the present time, so far as we know. It was also found that novel octaphenoxy- and/or hexaphenoxy-substituted phthalocyanine-based discotic liquid crystals exhibit spontaneous perfect homeotropic alignment in the tetragonal columnar mesophase. The corresponding polymer films showing the perfect homeotropic alignment at room temperature could be successfully prepared. Such marvelous films can be practically utilized as organic carrier transport materials and solar batteries.

90 citations


Journal ArticleDOI
TL;DR: The columnar mesophase as mentioned in this paper is characterized by a structure in which the disc shaped molecules are stacked one on top of the other to form columns, the different columns constituting a two-dimensional lattice.
Abstract: Since the discovery of discotic liquid crystals in 1977 [1] the field has grown rapidly with an estimated 3000 compounds belonging to this category. Generally these compounds have flat or nearly flat cores and surrounded by four to eight long chain substituents. A vast majority of these compounds exhibit the columnar mesophase. This phase is characterized by a structure in which thedisc shaped molecules are stacked one on top of the other to form columns, the different columns constituting a two-dimensional lattice. Several variants of the columnar structure have been identified-upright columns, tilted columns, hexagonal lattice, rectangular lattice, etc. The stacking of the discs within the column could be on the one extreme, liquid-like or on the other have a true long range order. Although X-ray measurements on quite a few compounds exhibiting these different structures have been reported, the temperature dependence of the various structural parameters does not seem to have received much attention. We ...

88 citations


Journal ArticleDOI
TL;DR: In this paper, the effects of the preparation conditions on the properties of the resulting composite such as ICP content, electrical conductivity, surface morphology, and electromagnetic interference shielding effectiveness (EMI SE) were investigated.
Abstract: Intrinsically conducting polymer (ICP)/textile composites were prepared by coating polypyrrole (PPy) or poly (3,4-ethylenedioxythiopene) (PEDOT) on the fabrics through chemical and electrochemical oxidation of pyrrole or EDOT. We investigated the effects of the preparation conditions on the properties of the resulting composite such as ICP content, electrical conductivity, surface morphology, and electromagnetic interference shielding effectiveness (EMI SE). The specific volume resistivity of the composite was as low as 0.3 Ω-cm, giving rise to about 36 dB of EMI SE over the wide range of frequency up to 1.5 GHz. We also prepared the elastic textile composites, exhibiting a monotonic increase of the electrical resistance with the elongation up to 50%. We, therefore, propose the elastic textile composite can be used as a strain sensor for large deformation.

77 citations


Journal ArticleDOI
TL;DR: In this article, a very low frequency range was used to measure the diffusion coefficient of n-pentyl (5CB) and n-octyl 8CB cyano biphenyls, providing characterization of mobile ions by diffusion coefficient or mobility, and their temperature dependence in the nematic phase and/or the smectic A phase.
Abstract: Permittivity dispersion measurements in a very low frequency range were made on n-pentyl (5CB) and n-octyl 8CB cyano biphenyls, providing characterization of mobile ions by the diffusion coefficient, or the mobility, and their temperature dependence in the nematic phase and/or the smectic A phase. Ionic conduction was confirmed in the nematic and the smectic A phases from the continuity of these temperature-dependent properties in the isotropic, the nematic, and the smectic A phases with reasonable changes at the transition temperatures. The Walden rule was found to be applicable to the ionic conduction in the nematic phase of 5CB without a pre-transitional phenomemon near the nematic-smectic phase transition, when appropriate mean values are taken for both the anisotropic mobility of ions and the anisotropic viscosity of the liquid crystal substance. It was also pointed out that care should be taken for the applicability of the Walden rule to liquid crystals in the case when the anisotropy of ionic condu...

55 citations


Journal ArticleDOI
TL;DR: In this article, the authors describe photovoltaic devices made with discotic liquid crystalline hexabenzocoronene and perylene dye molecules, which achieve an external quantum efficiency of up to 34% at monochromatic illumination at 490nm.
Abstract: Since the first demonstration of organic photovoltaic devices much progress has been made. Organic solar cells reach now power conversion efficiencies of up to 3% over the solar spectrum. The morphology of the active film is very important for efficient devices. Films spin-coated from blend solutions phase separate. The scale of the phase separation depends on the solvent, solubility of the materials and parameters of the spin-coating process such as speed, temperature, etc. If the morphology could be controlled on a molecular scale the efficiency of charge separation and transport could be expected to be substantially higher. The use of discotic liquid crystalline materials might help to reach this goal, because of their capacity to self-organise into columnar stacks. In this work we describe photovoltaic devices made with discotic liquid crystalline hexabenzocoronene and perylene dye molecules. Thin films have been produced by spin coating blends directly from solution. Devices with an external quantum efficiency (incident photon to current efficiency) of up to 34% at monochromatic illumination at 490nm have been achieved with a blend of hexaphenyl-substituted hexabenzocoronene (HBC-PhC 12 ) and a perylene diimide. Photovoltaic devices with other hexabenzocoronene derivatives as hole conductor show lower efficiencies. We attribute the lower device performance of the latter to the different film morphology occurring from spin coating of these materials. The aim of this work is to exploit the advantageous self-organising properties of HBC-perylene blends for solar cells.

46 citations


Journal ArticleDOI
TL;DR: In this paper, the basic working principle of both free-space and wave-guided liquid crystal optical devices along with novel device concepts using optical channel waveguides are reported.
Abstract: Liquid crystal devices to perform optical switching, filtering and to build optical crossconnects for wavelength division multiplexed optical communication systems are reviewed. Basic working principle of both devices already commercialised and those ones still at laboratory stage reported in the recent scientific literature are described. Devices based on liquid crystals and those ones made by using alternative technologies (MEMS, lithium niobate, semiconductors) are compared in terms of advantages and disadvantages. Technology issues to fabricate liquid crystal based photonic devices are discussed. Recent results of both free-space and waveguided based liquid crystal optical devices along with novel device concepts using optical channel waveguides are reported.

45 citations


Journal ArticleDOI
TL;DR: In this paper, a theoretical model for optimizing PDLC performance and fabrication process utilizing the polymerization-induced phase separation (PIPS) method is presented, and optical attenuation (OA) and polarization dependence loss (PDL) characteristics versus fabrication conditions.
Abstract: Dispersions of liquid crystals in polymeric matrices (PDLC) are used as light Variable Optical Attenuators (VOAs). Electronically controllable VOAs play a crucial role for channel power equalizers in WDM systems. This article describes the theoretical model optimizing PDLC performance and the fabrication process utilizing the polymerization-induced phase separation (PIPS) method, and presents the optical attenuation (OA) and polarization dependence loss (PDL) characteristics versus fabrication conditions. Fabricated VOAs have a large attenuation range (10–30 dB) and low insertion loss (IL) at a 1.55 µm wavelength (0.5 dB). Depending on the fabrication parameters, the OA, IL, and PDL are optimized. This device needs an applied voltage V90 of 10 to 70 Vrms for 10–100 µm PDLC thickness. The flatness of the optical characteristics of this device has also been measured in the C+L band.

40 citations


Journal ArticleDOI
TL;DR: In this article, the geometric and electronic structures of alkyl derivative C37H50N4O4 (PNX) molecule, (donor - spacer - acceptor), a candidate for a molecular rectifying device, has been investigated theoretically using ab initio quantum mechanical calculations.
Abstract: Recently, field of molecular electronics has attracted strong attention as a “post-silicon technology” to enable future nanoscale electronic devices. To realize this molecular device, unimolecular rectifying function is one of the most fundamental requirements using nanotechnology. In the present study, the geometric and electronic structures of alkyl derivative C37H50N4O4 (PNX) molecule, (donor – spacer – acceptor), a candidate for a molecular rectifying device, has been investigated theoretically using ab initio quantum mechanical calculations. The results suggest that in such donor-acceptor molecular complexes, while the lowest unoccupied orbital concentrates on the acceptor subunit, the highest occupied molecular orbital is localized on the donor subunit. After the optimization of the structure by B3LYP/6-31(d), the approximate potential differences for the optimized PNX molecule have been estimated at the B3LYP/6-311++G(d,p) level of theory, which achieves quite good agreement with experimentally rep...

35 citations


Journal ArticleDOI
TL;DR: Alignment techniques for calamitic liquid crystals are well developed and play a crucial role in liquid crystal devices as discussed by the authors, however, little attention has been paid to the alignment of discotic liquid crystals.
Abstract: Alignment techniques for calamitic liquid crystals are well developed and play a crucial role in liquid crystal devices. Comparatively little attention has been paid to the alignment of discotic liquid crystals. Only recently the integration of discotic liquid crystals into optical and electronic devices stimulated the development of new alignment techniques for discotic nematic and columnar mesophases. This mini-review attempts a brief summary of the challenges and recent success stories. Two new approaches to the alignment of discotic columnar mesophases will also be presented.

35 citations


Journal ArticleDOI
TL;DR: A series of three 4,4'-disubstituted-2,2'-bipyridines and corresponding mononuclear cis-dichloro palladium(II) complexes have been synthesized as mentioned in this paper.
Abstract: A series of three 4,4'-disubstituted-2,2'-bipyridines and the corresponding mononuclear cis-dichloro palladium(II) complexes have been synthesized. None of the ligands show mesomorphism. Upon their complexation to Pd(II) the peculiar structural arrangement characterized by intermolecular associations of the new derivatives induces mesogenic properties, confirming the new and exciting role of the coordination chemistry in metal-mediated formation of liquid crystals.

Journal ArticleDOI
TL;DR: In this paper, the uptake of benzoate anions from aqueous solutions by calcined and uncalcined layered double hydroxides (LDHs) is reported.
Abstract: The uptake of benzoate anions from aqueous solutions by calcined and uncalcined layered double hydroxides (LDHs) is reported. Adsorption (or sorption) isotherms have been determined at 25°C in the 0 to 100 mmol dm m 3 concentration range. The results showed that the calcined LDH sorbs 40 to 85% of the benzoate in solution in the concentration range usually found in industrial wastewater, and that the sorption capacity of this material is about 4 times greater than that observed for the parent LDH. The study of the sorption kinetics for the calcined material showed that it is a relatively slow process, which can be attributed to the fast regeneration of the calcined LDH with intercalated hydroxyl anions, followed by a slow process of anion exchange by benzoate. Collected solids after sorption present basal spacing close to 7.6 A, characteristic of intercalated hydroxyl anions or carbonate, suggesting a horizontal arrangement of benzoate in the interlayer.

Journal ArticleDOI
TL;DR: In this paper, the role of orientation on the rheology of discotic nematic liquid crystals is analyzed and the shear rheological properties exhibited by flow-aligning discotic mesophases are analyzed.
Abstract: This paper presents an analysis of the role of orientation on the rheology of discotic nematic liquid crystals. The shear rheological properties exhibited by flow-aligning discotic mesophases are c...

Journal ArticleDOI
TL;DR: A homologous series of azomesomesogens with lateral chloro group was synthesized in this article and the plot of transition temperatures against the number of carbon atoms in the alkoxy chain showed a steady fall in nematic-isotropic transition temperature.
Abstract: A homologous series of azomesomesogens, 2"[4-(4'-n-alkoxybenzoyloxy)-3-chloro phenylazo] naphthalene, with lateral chloro group was synthesized. All twelve homologues of the series synthesized exhibit enantiotropic nematic mesophase. The plot of transition temperatures against the number of carbon atoms in the alkoxy chain shows a steady fall in nematic-isotropic transition temperature.The mesogenic behavior of the present series is compared with other structurally related series to evaluate the effect of lateral chloro group on mesomorphism.

Journal ArticleDOI
TL;DR: A series of five new hexaalkylthiohexaazatriphenylenes 2a-e has been synthesized and their thermotropic behavior has been investigated.
Abstract: A series of five new hexaalkylthiohexaazatriphenylenes 2a-e has been synthesized. Their thermotropic behaviour has been investigated and compared with the corresponding series of hexaalkylthiotriphenylenes 1a-e and hexaalkylthiohexaazatrinaphthylenes 3a-e. Unexpectedly, hexaalkylthiohexaazatriphenylenes 2a-e, hexaalkylthiotriphenylenes 1d-e and hexaalkylthiohexaazatrinaphthylenes 3e, do not form columnar liquid crystalline mesophases.

Journal ArticleDOI
TL;DR: The use of discotic nematic liquid crystals instead of calamitic liquid crystals to improve the viewing angle of a liquid crystal display device has recently been reported in this article, where the design, synthesis, mesomorphic behaviour and structure-property relationship of Discotic Nematic Liquid Crystals based on benzene multiyne core is presented.
Abstract: The use of discotic nematic liquid crystals instead of calamitic nematic liquid crystals to improve the viewing angle of a liquid crystal display device has recently been reported. Compared to the large number of calamitic molecules showing nematic phase at room temperature, the number of disk-shaped molecules showing subambient discotic nematic phase N D are rare. In this paper we present the design, synthesis, mesomorphic behaviour and structure-property relationship of discotic nematic liquid crystals based on benzene multiyne core.

Journal ArticleDOI
TL;DR: The use of fluoro substituents in liquid crystals has proved essential for the development of materials with optimised properties for advanced high technology devices as discussed by the authors, which can have some remarkable effects on the important physical properties of liquid crystals.
Abstract: The use of fluoro substituents in liquid crystals has proved essential for the development of materials with optimised properties for advanced high technology devices. The small size and high polarity of a fluoro substituent can have some remarkable effects on the important physical properties of liquid crystals. Fluoro substituents can be usefully located at many different sites of a liquid crystal structure. Such a wide variety of possibilities allows for the advantageous tailoring of physical properties to meet the exacting demands of the various formats of application. This paper considers in detail the fascinating influence that fluoro substituents in the various locations have on these vital properties, and looks at some of the interesting aspects of the synthesis of such materials.

Journal ArticleDOI
TL;DR: In this article, the charge carrier mobility has been examined for a representative organic hole transport material TPD and a host material CBP, doped with a fluorescent dye, rubrene and Ir(ppy)3, by time-of-flight (TOF) technique.
Abstract: The Charge carrier mobility has been examined for a representative organic hole transport material TPD and a host material CBP, doped with a fluorescent dye, rubrene and Ir(ppy)3, by time-of-flight (TOF) technique. Decreasing of hole mobilities of the dye-doped films can be explained by a carrier-trapping model and the ionization potential difference of TPD and CBP. We successfully measured an electron mobility of the rubrene-doped TPD films, and Ir(ppy)3-doped CBP films, while the mobility could not measured non-doped TPD and CBP films. The EL process of the dye-doped systems is discussed in terms of the electron transfer properties of emission layer.

Journal ArticleDOI
TL;DR: In this paper, the azobenzene liquid-crystalline gel (LCG) films with macroscopic uniaxial alignment were prepared to investigate photoresponsive behavior.
Abstract: The azobenzene liquid-crystalline gel (LCG) films with macroscopic uniaxial alignment were prepared to investigate photoresponsive behavior By polarizing microscopy, fiber-like structures aligned in one direction were observed Furthermore, with a confocal laser scanning microscope (CLSM), it was confirmed that the fiber-like structures were formed even in the bulk of the LCGs When the LCG films were irradiated with UV light below Tg, changes in the microscopic surface morphology were observed, while no appreciable macroscopic change was observed On the other hand, when the LCGs were plasticized by suspending in solvents or heating above Tg, the LCG films showed macroscopic changes (eg bending) upon UV light irradiation The bending and unbending could be repeated just by changing the wavelength of the irradiation light It was suggested that the bending is induced by an absorption gradient which produces a volume difference between the front surface area and the bulk of the gel films

Journal ArticleDOI
TL;DR: In this paper, a novel liquid crystal display device employing discotic nematic material was developed, which has excellent viewing angle characteristics showing a wide and symmetric viewing angle profile, and has much less difference in the pixel capacitance between the ON and OFF states.
Abstract: Recently we developed [1] a novel liquid crystal display device employing discotic nematic material. This device exhibits the following improvements over a conventional twisted nematic (TN) display device using a calamitic nematic material. The device (i) is simple to fabricate and (ii) has excellent viewing angle characteristics showing a wide and symmetric viewing angle profile, (iii) has much less difference in the pixel capacitance between the ON and OFF states resulting in reduced cross talk problem. However the response time of the device is slower than conventional TN devices. An obvious solution to this problem is to reduce the viscosity of the material. To achieve this we have doped, in small concentrations, a long chain alkane compound to the parent room-temperature discotic nematic material. Systematic studies show that both the switch ON and switch OFF response times show a significant decrease, i.e., the device switches faster, in the case of the mixtures. It should be mentioned that wide and symmetric viewing angle characteristics remain unaffected by the addition of the dopant material. However both the switch ON and switch OFF response times are still an order of magnitude slower compared to that of conventional TN devices. Considering the fact that these response times are not very different from those for the STN displays, the achievement of symmetric and wide viewing angle characteristics with a simple fabrication process makes this device quite interesting. To make them attractive enough to be considered for commercial applications new materials with faster response have to be developed. Efforts in this direction are underway in our laboratory.

Journal ArticleDOI
TL;DR: In this paper, a mesogenic homologous series of Schiff base cinnamates comprising a naphthalene moiety were prepared by condensing different 4(4'-n-alkoxy) benzaldehydes with 2-amino naphalene.
Abstract: New mesogenic homologous series of Schiff base cinnamates comprising a naphthalene moiety were prepared by condensing different 4(4'-n-alkoxy cinnamoyloxy) benzaldehydes with 2-amino naphthalene All the synthesized compounds were characterized by combination of elemental analysis and spectroscopic techniques All the homologues synthesized exhibit mesomorphism The mesomorphic properties of the present series are compared with other structurally related series

Journal ArticleDOI
TL;DR: In this paper, the authors have varied the chemical structure of asymmetrically substituted triphenylenes with the purpose to enhance the spatial order and consequently to reduce the width of the energy distribution of the density of states.
Abstract: Columnar discotics display along the columnar axis unusually large mobilities for charge carriers. This fact can be exploited for instance in the areas of photoconductors and organic light emitting diodes. The transport takes place via hopping between localized transport sites. The theoretical analysis based on an analytical approach as well and on simulations predicts that the energetic distribution of the transport sites controls the particular dependence of the charge carrier mobility both on the temperature and the applied electric field. Narrow distributions cause the mobilities to increase and to become independent of temperature and field. A further prediction is that the mobility depends on the length of the columns. We have varied the chemical structure of asymmetrically substituted triphenylenes with the purpose to enhance the spatial order and consequently to reduce the width of the energy distribution of the density of states. Novel methods of macroscopical orientations of the columns were dev...

Journal ArticleDOI
TL;DR: In this article, it was shown that if the sample is kept in the glassy or crystalline state for several hours, the alignment inevitably changes to edge-on (planar or heterogeneously planar) in this phase.
Abstract: The results of our investigations show that on an untreated flat substrate, the discotic liquid crystals align side-on (or homeotropically) if the sample is slowly cooled from the isotropic phase. If the sample is kept in the glassy or crystalline state for several hours, the alignment inevitably changes to edge-on (planar or heterogeneously planar) in this phase. However, if the sample is heated from the glassy/crystalline phase, the alignment alters slowly from edge-on to side-on. This anchoring transition is dependent on the temperature and the substrate. On the other hand if the flat surfaces are treated with a polymer, the alignment achieved on cooling is also mostly side-on. A grooved surface or slightly uneven surface promotes the edge-on alignment (homogeneous and even heterogeneous). This type of alignment persists even when the surface is treated with a polymer. The side-on alignment once achieved is found to be thermodynamically stable in the discotic phase, where as the edge-on alignment has t...

Journal ArticleDOI
TL;DR: In this article, a poly(3,4-ethylenedioxythiophene)/gold (PEDOT/Au) nanocomposites were prepared by in-situ redox reaction using PEDOT in the neutral state and AuCl3 as an oxidant.
Abstract: Poly(3,4-ethylenedioxythiophene)/gold (PEDOT/Au) nanocomposites were prepared by in-situ redox reaction using PEDOT in the neutral state and AuCl3 as an oxidant. AuCl3 had a sufficient power to oxidize the neutral PEDOT film while it reduced to form gold nanoparticles in the polymer matrix. It was observed that the rate of redox reaction was strongly influenced by the solvent. Finally, the formation and coalescence of gold nanoparticles was clearly demonstrated by SEM and XPS experiments, and a rapid drop in film resistance was also monitored during the redox reactions.

Journal ArticleDOI
TL;DR: In this paper, it was shown that short pitch chiral nematogenic bimesogens may be synthesized that couple weakly via the bulk dielectric anisotropy, but extremely strongly via the flexoelectric effect t...
Abstract: Recently we have shown that short pitch chiral nematogenic bimesogens may be synthesized that couple weakly via the bulk dielectric anisotropy, but extremely strongly via the flexoelectric effect t...

Journal ArticleDOI
TL;DR: Chiral (3b ) and achiral ( 3a ) C 3 -symmetrical nitrogen centered amide disks were investigated with optical polarizing microscopy, differential scanning calorimetry and UV-Vis/circular dichroism spectroscopy as mentioned in this paper.
Abstract: Chiral ( 3b ) and achiral ( 3a ) C 3 -symmetrical nitrogen centered amide disks were investigated with optical polarizing microscopy, differential scanning calorimetry and UV-Vis/circular dichroism spectroscopy. Similar to the carbonyl centered amide disks 1a / b , only achiral compound 3a shows order in the liquid crystalline phase. Using the same techniques, two asymmetrical mono amide bisurea disks were investigated, one containing 6 "chiral urea" groups ( 4 ) and the other containing 3 "chiral amide" centers ( 5 ). These compounds do show supramolecular aggregation in dilute apolar solutions, featuring hysteresis in experiments investigating thermoreversibility; similar to C 3 -symmetrical trisurea compounds 2a / b .

Journal ArticleDOI
TL;DR: In this paper, the authors have attempted to simulate the field-induced alignment of the smectic A phase for the Gay-Berne model mesogen GB(4.4,20.0,1,1).
Abstract: As an aid to understanding the mechanism for the field-induced alignment of the smectic A phase we have attempted to simulate this process for the Gay-Berne model mesogen GB(4.4,20.0,1,1). The results for the quasi-dynamical behaviour of the alignment process obtained from a constant pressure-constant temperature Monte Carlo simulation are discussed. It is found that the molecules realign parallel to the field without destroying the layer structure and, more or less, as a monodomain in the simulations. This is qualitatively in agreement with the results obtained from recent deuterium NMR and small angle X-ray experiments. In addition, the relationship between the box shape and structures formed during the alignment process is discussed. The choice of box is found to be important for the simulation of the field-induced alignment process.

Journal ArticleDOI
TL;DR: In this paper, the conductivity, photoconductivity and mesophase ranges of hexaalkoxytriphenylene (HAT)-based discotic liquid crystals are all increased by adding one equivalent of {hexakis(4-nonylphenyl)dipyrazino[2,3-f:2′3′-h]quinoxalene} (PDQ9).
Abstract: The conductivity, photoconductivity and mesophase ranges of hexaalkoxytriphenylene (HAT)-based discotic liquid crystals are all increased by adding one equivalent of {hexakis(4-nonylphenyl)dipyrazino[2,3-f:2′3′-h]quinoxalene} (PDQ9). For some triphenylene derivatives, addition of PDQ9 induces liquid crystal behaviour, for HAT-based homopolymers the alignment characteristics are improved and for some HAT-based block copolymers, addition of PDQ9 induces microphase separation. The bonding interaction between the HAT and PDQ components is described as a CPI (complementary polytopic interaction) and is best modelled as an atom by atom sum of van der Waals and multipolar terms. Although strong it does not detectably perturb the electronic structure of either component and there is no charge-transfer.

Journal ArticleDOI
TL;DR: The effect of the introduction of the furan and furan-based systems into the molecular structure of liquid crystals on the appearance of the mesophases and their physico-chemical properties is discussed and compared with that of other well-known molecular fragments.
Abstract: The effect of the introduction of the furan and furan-based systems into the molecular structure of liquid crystals on the appearance of the mesophases and their physico-chemical properties is discussed and compared with that of other well-known molecular fragments.

Journal ArticleDOI
TL;DR: In this paper, the self-assembly and lyotropic mesomorphism of guanosine derivatives are reviewed and a review of the electrical properties of ribbon-like aggregates has been presented.
Abstract: The self-assembly and lyotropic mesomorphism of guanosine derivatives are reviewed. Natural and synthetic guanosine nucleotides self-assemble into columnar aggregates based on G-quartets; at the appropriate concentrations these aggregates form, in water, lyotropic mesophases of the cholesteric and hexagonal type. Lipophilic derivatives undergo different types of self-assembly: in the presence of alkali metal ions they form, in organic solvents, columnar structures and lyomesophases similar to those observed for the hydrophilic derivatives; in the absence of ions they form instead ribbon-like aggregates which give rise to new types of lyotropic phases. The ribbon-like aggregates have interesting electrical properties.