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We have developed a new strategy for the preparation of a light-responsive ionic liquid crystal (LC) that shows photo-switchable proton conduction. The ionic LC consists of a bowl-shaped calix[4]arene core ionically functionalized with azobenzene moieties. The non-covalent architectures were obtained by the formation of ionic salts between the carboxylic acid group of an azo-derivative and the terminal amine groups of a calixarene core. The presence of ionic salts results in a hierarchical self-assembly process that extends to the formation of a nanostructured lamellar LC arrangement (smectic A phase). In this LC phase, the ionic LC calixarene is able to display proton conductive properties, since the ionic nanosegregated areas (formed by the ionic pairs) generate the continuous channels that favor proton transport. The optical and photo-responsive properties were studied by UV-Vis spectroscopy, demonstrating that the azobenzene moieties of the ionic LC undergo reversible (E)-to-(Z) isomerization by irradiation with UV light. Interestingly, this (E)-to-(Z) photoisomerization results in a decrease of the proton conductivity values since the bent-shaped (Z)-isomer disrupts the lamellar LC phase. This isomerization process is totally reversible and leads to an ionic LC material with unique photo-switchable proton conductive properties.

Deposition of the top-contact electrode to create large-area electrode | monolayer | electrode junctions represents a contemporary challenge to the integration of molecular electronic phenomena into device structures. Here, a top contact electrode is formed on top of an organic monolayer over a large area (cm2) by two simple, sequential self-assembly steps. Initial self-assembly of 4,4′-(1,4-phenylenebis(ethyne-2,1-diyl))dianiline onto gold-on-glass substrates gives high-quality monolayers. The exposed amine functionality is subsequently used to anchor uncapped gold nanoparticles deposited in a second self-assembly step. These uncapped gold nanoparticles are prepared by thermolysis of lipoic acid stabilized gold nanoclusters and contain gold oxide (≈9%) that provides stability in the absence of an organic capping ligand. This two-step procedure results in full coverage of the monolayer by the densely packed gold nanoparticles, which spontaneously condense to give a semi-continuous film. The electrical properties of these junctions are determined from I–V curves, revealing uniform electrical response and absence of metallic short-circuits or evidence of damage to the underlying molecular monolayer. These promising electrical characteristics suggest that the deposition of uncapped gold nanoparticles on suitably functionalized molecular monolayers provides a path for the fabrication of molecular electronic devices using simple methodologies.

Two non‐amphiphilic star‐shaped 2,4,6‐tris(1,2,3‐triazol‐4‐yl)‐1,3,5‐triazines showing different behavior in terms of self‐assembly and luminescent properties are described. They aggregate in the liquid phase to form low‐dimensional nanostructures with a variety of morphologies, such as spherical particles, one‐hole hollow spheres, toroids, twisted fibers or helical nanotubes, just by varying the conditions of a straightforward reprecipitation method. Aggregation has an opposite effect concerning the fluorescent properties of the proposed compounds, either causing the enhancement or the quenching of the emission after the self‐assembly. Quantum chemical calculations have been also performed to assist in the structural and electronic characterization of the two star‐shaped compounds.

Computational and experimental studies unravel the structural and electronic properties of a novel supramolecular liquid crystal built through a hierarchical assembly process resulting in an H‐bonded melamine rosette decorated with peripheral triphenylenes. The six‐fold symmetry of the mesogen facilitates the formation of a highly organized hexagonal columnar mesophase stable at room temperature. X‐ray diffraction and electron density maps confirm additional intra‐ and intercolumn segregation of functional subunits, and this paves the way for 1D charge transport. Indeed, hole mobility has been measured and found to be higher than for related mesogens. DFT calculations of HOMO and LUMO levels and parameters such as reorganization energy and transfer integral of the rosette structure have been achieved, and not only validate the columnar organization but also establish the way it translates into a favorable electronic architecture and molecular orbital interactions to promote charge carrier mobility.

The synthesis and liquid crystalline behavior of new calixarene Schiff base derivatives are reported. The materials were obtained by reaction of a tetraaminocalix[4]arene derivative with three aldehydes as mesogenic promotor moieties: 4‐(4′‐decyloxybenzoyloxy)benzaldehyde (A), 4‐(4′‐decyloxybenzoyloxy)salicylaldehyde (B) and 4‐(3′,4′‐didecyloxybenzoyloxy)salicylaldehyde (C). All of the compounds exhibit liquid crystalline properties and these were studied by optical microscopy, DSC and X‐ray diffraction. The relationship between the structure and the mesomorphic behavior of the compounds is discussed. The binding recognition and selectivity towards cations have been studied by absorption and fluorescence spectroscopy.

We report a new family of multifunctional liquid-crystalline porphyrin-core dendrimers that have coumarin functional groups around the porphyrin core. Porphyrin metalation strongly affects the photophysical properties, and therefore Zn and Cu derivatives have also been prepared. All the synthesized dendrimers form a nematic discotic mesophase. Their high tendency for homeotropic alignment makes these dendrimers excellent candidates for device applications, owing to their easy processability, spontaneous alignment between electrodes, and self-healing of defects because of their dynamic nature. The charge mobility values of these materials are the highest ever reported for a nematic discotic phase. Moreover, these values are similar to the highest values reported for ordered columnar mesophases, and this shows that a supramolecular organization in columns is not necessary to achieve high charge mobility.

A straightforward synthesis of mesogenic pyrazoles starting from benzaldehydes by a combination of efficient Henry and Michael reactions led to novel supramolecular liquid crystals. The mesogens are fluorescent 3,5-dimethyl-4-(di or trialkoxyphenyl)pyrazoles and, in spite of the tapered shape of these molecules and their structural simplicity (only one phenyl ring), columnar liquid-crystal phases were formed that are stable at room temperature. The self-assembled structure was studied by XRD and the columnar cross section contains two molecules on average with an antiparallel arrangement of pyrazoles interacting through hydrogen bonds. In contrast, the single-crystal structure of a trimethoxy analog did not show hydrogen-bonded pyrazoles but chains of head-to-tail arranged molecules.

The synthesis and characterisation of a family of block codendrimers consisting of highly versatile mesogenic and carbazole-containing 2,2-bis(hydroxymethyl)propionic acid (bis-MPA) dendrons are reported. The liquid-crystal behaviour was investigated by means of differential scanning calorimetry, polarised-light optical microscopy and X-ray diffraction. Depending on the chemical structure of the constituent dendrons, the codendrimers show lamellar or columnar mesophases. On the basis of the experimental results, models both at the molecular level and in the mesophase are proposed. The physical properties of the block codendrimers derived from the presence of the carbazole moiety in their structure were investigated: photoluminescence in solution and in the mesophase, electrochemical behaviour and hole transport. Electrodeposition of carbazole dendrons afforded a globular supramolecular conformation in which the mesogenic molecular side plays a key role.

The design, synthesis, and investigation of two series of side-on dendrimers displaying nematic liquid crystal behavior at room temperature are described. The dendritic structures are derived from poly(amidoamine) (PAMAM-(NH2)n) or poly(propylene imine) dendrimers (PPI-(NH2)n) (with n = 4, 8, 16, 32, and 64) containing lateral attached mesogenic units in the periphery. The materials are characterized by 1H, 13C nuclear magnetic resonance (NMR) spectroscopy, matrix-assisted laser desorption/ionization-mass (MALDI-TOF MS) spectrometry, differential scanning calorimetry (DSC), polarized optical microscopy (POM), and x-ray diffraction spectroscopy. All dendrimers exhibit nematic mesophase behavior at room temperature. Conoscopic studies reveal that the nematic phase is uniaxial. The relationship between the structure of the two dendrimer series and the mesomorphic behavior is discussed.

A star-shaped tris(triazolyl)triazine is shown to establish hydrogen-bond interactions with polycatenar benzoic acids. The formation of hydrogen-bonded triazine/acid complexes has been demonstrated both in solution and in bulk by different techniques. The complexes, mainly formed by nonmesogenic components, all show enantiotropic hexagonal columnar mesomorphism, which relies on the formation of hydrogen-bond complexes in a triazine/acid ratio of 1:3. This approach combines the straightforward synthesis of a nonmesomorphic triazine core by click chemistry, and the preparation of a supramolecular complex, providing a much more convenient route than covalent synthesis to modify the periphery of triazine discotics and thus to modulate their functionality.

A series of new liquid-crystalline dendrimers is synthesized from hexa(4-hydroxyphenyloxy)cyclotriphosphazene as the central core and bis(MPA) as a branching agent. The dendrimers are functionalized with azobenzene mesogenic moieties. The monodisperse nature of the dendrimers is confirmed by 1H and 31P{1H} NMR and by matrix assisted laser desorption/ionization (MALDI) mass spectrometry (MS). A study of the thermal properties reveals mesomorphic behavior. All of the materials exhibit a lamellar phase and this is confirmed to be smectic A in nature by X-ray diffraction. A nematic phase is also observed for the dendrimers that contain 4-cyanoazobenzene. A calamitic arrangement in which the mesogenic moieties point both upwards and downwards with respect to the cyclotriphosphazene core is proposed to explain the mesomorphic properties. The introduction of photochromic moieties leads to a photoresponse for these materials. The response to linearly polarized light is studied and an order parameter of about 0.5 is measured for dendrimer G1-Azo-3.

Control of the self-assembly of small molecules to generate architectures with diverse shapes and dimensions is a challenging research field. We report unprecedented results on the ability of ionic, bent dendritic molecules to aggregate in water. A range of analytical techniques (TEM, SEM, SAED, and XRD) provide evidence of the formation of rods, spheres, fibers, helical ribbons, or tubules from achiral molecules. The compact packing of the bent-core structures, which promotes the bent-core mesophases, also occurs in the presence of a poor solvent to provide products ranging from single objects to supramolecular gels. The subtle balance of molecule/solvent interactions and appropriate molecular designs also allows the transfer of molecular conformational chirality to morphological chirality in the overall superstructure. Functional motifs and controlled morphologies can be combined, thereby opening up new prospects for the generation of nanostructured materials through a bottom-up strategy.

Novel liquid crystal (LC) dendrimers have been synthesised by hydrogen bonding between an s-triazine as the central core and three peripheral dendrons derived from bis(hydroxymethyl)propionic acid. Symmetric acid dendrons bearing achiral promesogenic units have been synthesised to obtain 3:1 complexes with triazine that exhibit LC properties. Asymmetric dendrons that combine the achiral promesogenic unit and an active moiety derived from coumarin or pyrene structures have been synthesised in order to obtain dendrimers with photophysical and electrochemical properties. The formation of the complexes was confirmed by IR and NMR spectroscopy data. The liquid crystalline properties were investigated by differential scanning calorimetry, polarising optical microscopy and X-ray diffractometry. All complexes displayed mesogenic properties, which were smectic in the case of symmetric dendrons and their complexes and nematic in the case of asymmetric dendrons and their dendrimers. A supramolecular model for the lamellar mesophase, based mainly on X-ray diffraction studies, is proposed. The electrochemical behaviour of dendritic complexes was investigated by cyclic voltammetry. The UV/Vis absorption and emission properties of the compounds and the photoconductive properties of the dendrons and dendrimers were also investigated. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A series of supermolecular liquid crystals has been synthesized by combining phosphorus dendrimers of the zero, first, and fourth generations with sulfonamide derivatives, thus generating dendromesogens bearing 6, 12, and 96 mesogenic units on their surfaces. The relevant reactions could be monitored by 1H, 19F, and 31P{1H} NMR spectroscopies. The thermal and mesomorphic properties of the products have been studied by optical microscopy, differential scanning calorimetry, and X-ray diffraction. All of the new macromolecules prepared in this work have been found to show mesomorphic properties over a wide temperature range; moreover, for all of the compounds, the columnar mesophases observed were maintained or vitrified at room temperature. On increasing the generation of these dendromesogens, mesophases appear at lower temperatures and remain stable over a wider temperature interval. In all cases, on the basis of X-ray analysis, a cylindrical symmetry of the molecules can be proposed to promote the supramolecular columnar arrangement observed in the mesophases. In this type of model, the height of the dendrimer clearly increases with increasing dendrimer generation, whereas its crosssectional area increases only slightly, probably due to compression of the highly hyperbranched structures as a consequence of their progressive steric constraints. The mesomorphic arrangement is governed by the peripheral sulfonamide units.

Cyclic trinuclear gold(I) complexes with chiral 3,5-diarylpyrazolate ligands have been synthesized and characterized with the aim of obtaining helical columnar liquid-crystal phases as a way to control the stacking geometry and orientation of the trigold metallacycle in the bulk phase. The compounds bear n-decyloxy- and/or (S)-3,7-dimethyloctyloxy terminal groups in a number varying from twelve to eighteen. The compounds behave like isotropic glasses, crystalline solids, or columnar liquid crystals (of hexagonal or rectangular symmetry), with isotropization temperatures close to room temperature. In the case of the compound bearing nine n-decyloxy- and nine (S)-3,7-dimethyloctyloxy terminal groups, a helical columnar phase is obtained that exhibits a well-formed hexagonal bidimensional lattice made of columns that consist of molecules stacked at regular distances and mutually rotated by 40° in a helical mode. Thin films display emission bands at room temperature in the blue region of the visible spectra, regardless of the phase or the molecular structure.

A polymer network is prepared by the thiol-yne photopolymerization of multifunctional dendrimer with a tetrathiol crosslinker. The network obtained shows a liquid crystalline phase at room temperature, which has been characterized by optical microscopy, differential scanning calorimetry, and X-ray diffraction. Photoinduced deformation of uniaxially aligned free-standing films of the photocrosslinked material has been demonstrated. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mesomorphic arylsulfonamide derivatives containing four long alkyl chains and polar groups (fluoro, cyano or amino) have been synthesized and characterized by polarized optical microscopy, differential scanning calorimetry, and X-ray diffraction on the mesophase. Studies of the supramolecular organization of these molecules have allowed a better understanding of the noncovalent driving forces (dipole··· dipole and hydrogen-bonding interactions) responsible for the self-assembly, which is mainly due to the presence of the polar groups.

The synthesis and characterization of ionic liquid crystalline dendritic polymers based on the ammonium salts of commercially available poly(propylene imine) (PPI), poly(amidoamine) (PAMAM), poly(ethyleneimine) (PEI), and the fully methylated PEI (PEIMe) with 5-(4-cyanobiphenoxy)pentanoic acid (CBPA) are reported. The occurrence of proton transfer from the carboxylic acid to the amine groups is confirmed using IR and NMR techniques. The mesomorphic behavior is investigated by means of differential scanning calorimetry, polarizing optical microscopy, and X-ray diffractometry. Although CBPA exhibits monotropic nematic mesomorphism, all ionic complexes display enantiotropic liquid crystal properties. The relationship between the mesomorphism of the complexes and their structure is discussed. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

[EN]: A divergent approach was used for the synthesis of dendritic structures based on a cyclotriphosphazene core with 12 or 24 hydroxyl groups, by starting from [N3P3(OC6H4OH-4)6] and using an acetal-protected 2,2-di(hydroxymethyl)propionic anhydride as the acylating agent. Hydroxyl groups in these first- and second-generation dendrimers, G1-(OH)12 or G2-(OH)24, were then condensed in turn with mono- or polycatenar pro-mesogenic acids to study their ability to promote self-assembly into liquid crystalline structures. Reactions were monitored by using 31P{1H} and 1H NMR spectroscopy and the chemical structure of the resulting materials was confirmed by using different spectroscopic techniques and mass spectrometry (MALDI-TOF MS). The results were in accordance with monodisperse, fully functionalised cyclotriphosphazene dendrimers. Thermal and liquid crystalline properties were studied by using optical microscopy, differential scanning calorimetry and X-ray diffraction. The dendrimer with 12 4-pentylbiphenyl mesogenic units gives rise to columnar rectangular organisation, whereas the one with 24 pentylbiphenyl units does not exhibit mesomorphic behaviour. In the case of materials that contain polycatenar pro-mesogenic units with two aromatic rings (A4 vs. A5), the incorporation of a short flexible spacer connected to the periphery of the dendron (acid A5) was needed to achieve mesomorphic organisation. In this case, both dendrimer generations G1 A5 and G2 A5 exhibit a hexagonal columnar mesophase. [ES]: En este trabajo se ha usado un método divergente para obtener estructuras dendríticas no convencionales basadas en un núcleo de ciclotrifosfazeno con doce o veinticuatro grupos hidroxilo, partiendo de [N 3P3(OC6H4OH-4)6] y utilizando como agente acilante un anhídrido protegido derivado del ácido 2,2-bis(hidroximetil)propiõnico. Los grupos hidroxilo en estos dendrímeros de primera y de segunda generaciõn, G1-(OH) 12 or G2-(OH)24, se condensaron con ácidos promesõgenos

What a core-ker! By the appropriate combination of promesogenic bent-core structures and the C60 unit, lamellar polar liquid-crystal phases were induced (see scheme). The supramolecular organization of the functional fullerene-based assemblies, the temperature range of the soft phase, the stabilization of the mesophase-like order at room temperature, and the molecular switching under an electric field can be tuned, depending on the molecular structure.

The stacking order and distance in columnar phases of triindole-based liquid crystals is controlled by an ethynyl linker (see picture; orange rod) between the central triindole core (green) and the peripheral flexible chains of a discotic mesogen. Hole (h) mobility is very high even if the stacking distances is not very short and the conjugated system is not particularly extended.

[EN]: New liquid crystals having a non-conventional structure have been synthesised from a six-armed cyclotriphosphazene core, [N3P3(OC6H4OH-4)6], which was condensed with polycatenar acids. Reactions were monitored by 31P{1H} and 1H NMR spectroscopy and the chemical structure of the resulting materials was confirmed by different spectroscopic techniques and mass spectrometry (MALDI-TOF). Results were in accordance with monodisperse, fully functionalised cyclotriphosphazenes. Thermal and mesomorphic properties were studied by optical microscopy, differential scanning calorimetry and X-ray diffraction. All of the synthesised phosphazenes, substituted with benzyl ether chains, show a high thermal stability and exhibit mesomorphic properties, which depend on the number and type of alkyl terminal chains located at the periphery of the mesogens. Mesomorphic properties range from Colh for cph-A1 and cph-A2 to a cubic phase detected for cph-A3, which has the larger number of alkyl chains. Furthermore, helical order was detected on X-ray data of cph-A2, which has chiral branched chains. Circular dichroism spectra of annealed films at mesophase temperature show a signal attributed to the chiral helical arrangement of the mesogenic chromophores., [ES]: En este trabajo se han sintetizado nuevos cristales líquidos que tienen una estructura no convencional a partir de un núcleo de ciclotrifosfazeno, [N3P3(OC6H4OH-4)6], por condensación con ácidos policatenares. Las reacciones fueron monitorizadas por RMN de31P{1H} y1H, y la estructura química de los materiales resultantes se determinó por diferentes técnicas espectroscópicas y espectrometría de masas (MALDI-TOF). Los resultados están de acuerdo con ciclotrifosfazenos monodispersos y completamente funcionalizados. Las propiedades térmicas y mesomorfas de todos los compuestos se estudiaron por microscopía óptica, calorimetría diferencial de barrido y difracción de rayos-X. Todos estos ciclofosfazenos, que tienen grupos laterales con cadenas bencil éter, tienen una alta estabilidad térmica y muestran propiedades mesomorfas que dependen del número y tipo de cadenas alquílicas localizadas en la periferia de los mesógenos. Las mesofases observadas varían de Colhpara los compuestos cph-A1 y cph-A2 a cúbica para cph-A3, con un mayor número de cadenas alquílicas. Además, mediante difracción de rayos-X, se detectó un orden helicoidal en el compuesto que tiene cadenas quirales, cph-A2. Los espectros de CD de películas curadas a la temperatura de mesofase muestran una señal asignada a una disposición helicoidal quiral de los cromóforos mesógenos.

A molecular tug of war between non- and semifluorinated alkyl chains (see picture) occurs when they are forced together by ionic attachment to a poly(propylene imine) dendrimer. Unexpected mesomorphic properties appear as a consequence of the competition of both substituents to control the supramolecular organization of the molecules.

The synthesis and characterization of a series of nematic SWNT-polyazomethine composites are described. The composites were prepared by in situ polymerization in the presence of 1 wt % of chemically modified SWNTs in such a way that they were either dispersed or covalently bonded to the polymeric matrix. The presence of the SWNTs did not alter the thermal behavior of the polymer matrix and, therefore, highly oriented fibers could be melt-extruded from the composites at moderate temperatures, as revealed by structural and morphological studies. Preliminary tests on tensile properties indicate that strength and stiffness were improved when compared with fibers without CNTs, particularly when SWNTs were covalently bonded to the polymeric matrix.

An efficient procedure to create oriented polymer films with strongly anisotropic properties is described. It is based on a two-step process combining a photochemical and a thermal aligning step. The orientation of the polymer parallel or perpendicular to linearly polarised incident light can be adjusted. The method presented allows for simple fabrication of films with anisotropic absorption and emission characteristics with a dichroism of 0.7 and a fluorescence anisotropy of about 8.

A liquid crystalline homopolymer that has photoisomerizable methoxyazobenzene groups in the side chain has been synthesized and characterized. Thin films of the nematic glassy phase of this polymer have been processed in order to study the absorption spectra and the vibrational and electronic circular dichroism responses by irradiation with 488 nm circularly polarized light (CPL). Selective reflection of visible light demonstrates that the irradiation of this glassy nematic azopolymer induces a helix as a consequence of the chiral arrangement of the azobenzene units. Moreover, a wedge cell with an aligning layer for planar orientation was filled with the polymer with the aim of investigating the change in the macroscopic optical properties and optical textures of the azopolymer on irradiation with CPL. The transfer of chirality from CPL to azopolymer through chiral conformations is proposed as a model for explaining the supramolecular chirality.

Octopolar tris[(phenyl)ethynyl]benzenes with high second-order nonlinear optical (NLO) activity form discotic liquid-crystalline mesophases whose properties depend on the length of the alkoxy chains. The molecules self-organize in a non-centrosymmetric fashion in the bulk phase which enables the construction of a simple, efficient, NLO device (see picture).