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El silicato de sodio es una sal cuya producción a nivel industrial se basa en la fusión a más de 1000ºC de carbonato de sodio y arena de cuarzo (sílice). Tras la fusión, el silicato que se genera no es soluble en condiciones de presión atmosférica, por lo que su utilidad es limitada. Para solubilizarlo, se emplea alta presión y temperatura de tal manera que se obtienen silicatos líquidos, a partir de los cuales, mediante un proceso de secado controlado, se obtienen silicatos sólidos solubles. Entre sus aplicaciones, se encuentra su uso como agente defloculante. Los agentes defloculantes se emplean en la manufactura de productos cerámicos a partir de pastas arcillosas con el objetivo de mejorar las características reológicas de la barbotina, que es una suspensión de arcilla en agua, y es la forma en la que la arcilla se encuentra a lo largo de estos procesos industriales. En este proyecto se ha analizado la actividad defloculante de tres tipos diferentes de silicatos sólidos solubles según su relación en peso (RP SiO2/Na2O) en ocho pastas distintas, fijando las condiciones de la defloculación según las especificaciones de cada proceso industrial, diferente para cada pasta. Además, se ha evaluado también la actividad conjunta del silicato con diferentes aditivos, que actúan sinérgicamente con este para mejorar la defloculación. Por último, se han llevado a cabo ensayos de sobredefloculación para conocer el comportamiento de las barbotinas en dosis anormalmente altas de defloculante. Los resultados revelan que el silicato RP 1.7 es el que tiene un mejor desempeño como defloculante, seguido del silicato Rp 2. El silicato Rp 1 da, en general, los peores resultados. Además, se observa que la adición de aditivos siempre iguala o mejora la defloculación, respecto al silicato base. Cabe destacar que, si bien el silicato Rp 1.7 con poliacrilato de sodio como aditivo es el que mejor funciona para muchas de las pastas empleadas, el silicato y aditivo que mejor funciona depende

La fabricación de silicatos solubles, tantos sódicos como potásicos, y sus derivados es la principal actividad de la empresa zaragozana Industrias Químicas de Ebro. En la fabricación de dichos compuestos es frecuente la aparición de un sólido de color blanco que ha sido caracterizado como octosilicato sódico, un silicato con estructura laminar. En un primer momento se pensó que el subproducto interfería en la fabricación de los silicatos y los primeros estudios pretendían eliminar su aparición. Se estudiaron varios factores en la fabricación de los silicatos pero en ninguno de los casos se consiguió el objetivo. Es por ello que, tras no poder evitar la aparición del mismo, se pensó en el octosilicato como un subproducto aprovechable debido a su posibilidad de valorización que reside en su espacio interlaminar. En el presente Trabajo Fin de Master se ha buscado, en primer lugar, la optimización de la producción del octosilicato, estudiando diversas variables que afectan al rendimiento de la reacción como son la temperatura, el tiempo y la concentración de siembra añadida. Posteriormente, el objetivo se ha centrado en estudiar la valorización del octosilicato mediante la incorporación de moléculas orgánicas que permitan aumentar el espacio interlaminar, produciendo así materiales con una mayor resistencia, y la comparación con otros silicatos laminares comerciales. Por último, estas reacciones de valorización han sido llevadas a cabo en una planta piloto para comparar su rendimiento, con el obtenido en el laboratorio, y estudiar la viabilidad del proceso de cara a una futura producción industrial.

New poly(propylene imine) (PPI) dendrimers modified at the periphery with mesomorphic 4-cyanobiphenyl units and cinnamate- or coumarin-based photoactive moieties were synthesised and structurally characterised. The photoactive moieties were structurally designed to be liquid crystalline compatible and to reduce the tendency towards crystallisation of the final material. Thermal and liquid crystal properties were studied by POM, DSC, TGA and XRD. The results show that all dendrimers displayed a smectic A mesophase. Dendrimers with high transparency in the visible region but with different absorption spectra were obtained, rendering materials that are easy to monitor in light-irradiation experiments.

The self-assembly of axial dipolar subphthalocyanine molecules in the presence of electric fields leads to uniaxially oriented columnar liquid crystalline materials that exhibit permanent polarization.

A polar response in a lyotropic columnar nematic material is reported. The material accommodates bowl-shaped molecules with strong axial dipole moments in column segments without head-to-tail invariance. Optical second-harmonic-generation methods confirm that the nematic columns align unidirectionally under an applied electric field and the material develops remnant macroscopic polarization observable for hours. The switching takes place by a flip of the columns.

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.

Two series of new V-shaped acids derived from 1,3,4-oxadiazoles are described. These acids were used to prepare supramolecular complexes through hydrogen bonding with 2,4-diamino-6-dodecylamino-1,3,5-triazine in a 3:1 ratio, respectively. The formation of the complexes was studied by infrared and NMR techniques. The thermal behaviour and mesomorphic properties of all the complexes were investigated by polarized light optical microscopy, differential scanning calorimetry and X-ray diffraction. Hexagonal and rectangular columnar mesophases were observed for all complexes at room temperature, without evidence of crystallization. The results of circular dichroism studies allowed us to propose that in the liquid crystalline state these materials adopt a helical columnar organization and this chirality can be controlled by irradiation with CPL. Furthermore, the complexes display strong blue luminescence in solution and in the mesophase. © the Partner Organisations 2014.

A new luminescent ionic liquid crystal, called Ipz-2, has been synthesised and its mesophase behaviour and also at the air-liquid interface has been studied and compared with Ipz, another ionic pyrazole derivative, with a similar molecular structure, previously studied. The X-ray diffraction pattern shows that Ipz-2 exhibits hexagonal columnar mesomorphism, while Ipz adopts lamellar mesophases. Langmuir films of both compounds are flat and homogeneous at large areas per molecule, but create different supramolecular structures under further compression. Ipz-2 Langmuir films have been transferred onto solid substrates, and Atomic Force Microscopy (AFM) images of the Langmuir-Blodgett films have shown that large columnar structures hundreds of nm in diameter are formed on top of the initial monolayer, in contrast with well-defined trilayer LB films obtained for Ipz. Our results show that Ipz-2 has a tendency to stack in columnar arrangements both in liquid crystalline bulk and in Langmuir and Langmuir-Blodgett films. © 2012 Elsevier Inc.

Experimental data are combined with theoretical calculations to study the stability of the boat conformation of the pyrazabole ring. For the experimental studies, new BH2- and BF2-pyrazaboles disubstituted with iodo or ethynyl groups at the 2-and 6-positions have been prepared and structurally characterized. We have found different molecular structures and crystal packings depending on the substituents. The iodo derivatives have a bent molecular shape due to the boat conformation of the pyrazabole ring, and the molecules are arranged in stacks with the same conformation (all-up or all-down boat conformation) along the crystallographic b axis. Stacks of molecules with the same conformation interact in a plane by means of iodo-iodo short contacts. However, the ethynyl derivatives are formed by bent-shaped molecules for BH 2 and planar structures for BF2. Density functional theory and ab initio calculations have been performed on these compounds and on unsubstituted analogues to understand the effect of substituents on the conformation, inversion barrier, and NMR chemical shifts. The results of these calculations were compared with the experimental results. Theoretically, the boat conformation is an energy minimum, with the planar and chair conformations as transition states in an energy diagram. In solution, the compounds are in a boat conformation (with a boat-to-boat dynamic equilibrium) irrespective of their crystal structures. © 2008 American Chemical Society.

Boron coordination compounds with a roof-shaped morphology (see structure) exhibit unusual liquid-crystalline behavior with a transition (represented by the red arrow) from a nematic mesophase with similar characteristics to those of some bent-core liquid crystals to a compact lamellar phase with a chiral organization (see microphotographs of the two phases).

Several new cis-[RhCl(CO)2(Ln)] complexes have been prepared using different polycatenar pyrazole ligands (Ln) in order to obtain columnar liquid crystalline arrangements. The topology of the ligand plays an essential role, and a mesophase is induced at room temperature from a nonmesogenic pyrazole only when it is symmetrically substituted with six decyloxy chains. The single-crystal structure of a methoxy-substituted analogue, 3,5-bis(3,4,5-trimethoxyphenyl)pyrazole, is formed by globular tetrameric structures held together by H-bonding. However, parallel dimers are present in the corresponding cis-chlorodicarbonylrhodium(I) complex, a situation that explains the induction of a columnar mesophase in the decyloxy-substituted complex. The XRD pattern of the mesophase is consistent with a hexagonal symmetry in which the columns are formed by molecules assembled in an antiparallel mode. The crystal-to-mesophase transition was also detected by spectroscopic techniques as a shift in the IR carbonyl stretching bands and the appearance of a charge-transfer band in the absorption spectrum with thermochromic behavior.