Showing papers in "Journal of Materials Chemistry in 1994"
TL;DR: In this paper, the authors have suggested the pair formation of transverse dipole moments in adjacent smectic layers as the cause of antiferroelectricity in liquid crystals.
Abstract: In a brief history of the discovery of antiferroelectricity in liquid crystals, the important role played by tristable switching, i.e. an electric field induced phase transition from antiferroelectric SCA* to ferroelectric SC*, has been emphasised and the antiferroelectric herringbone structure of SCA* has been presented. Then we have explained how to identify the subphases in the SC* region, e.g. SCγ*, SCα*; the clarification of the subphase structures is essential for understanding antiferroelectricity in liquid crystals. After summarizing the evidence for the SCA* structure presented, we have suggested the pair formation of transverse dipole moments in adjacent smectic layers as the cause of its antiferroelectricity, showing that the smectic layer is much closer to the usual picture of molecules lying on equidistant planes; the packing entropy due to the sinusoidal density wave character stabilizes ferroelectric SC*. The competition between the interactions stabilizing SCA* and SC* is responsible for the occurrence of several varieties of ferrielectric and antiferroelectric subphases, which constitutes the Devil's staircase. We have further suggested that the essentials of the SCα* phase are its considerably reduced ability to form SCA* and SC*. At least when the spontaneous polarization is zero, SCα* is a smectic C-like phase with molecular tilting that is non-correlated on the visible wavelength scale When the spontaneous polarization is not zero, as suggested by Prost and Bruinsma recently, a novel type of Coulomb interaction between smectic layers due to the collective polarization fluctuations causes the antiferroelectricity in the high-temperature region of SCα*; the competition between this antiferroelectricity and the SC* ferroelectricity may form another staircase, causing the complexity in SCα*. Applications and some future problems have been described in the final section.
478 citations
TL;DR: In this paper, a consistent set of pair potentials has been derived empirically by fitting to the experimentally measured lattice properties of a series of binary metal oxides, which can be used to make a more reliable determination of ion polarisabilities.
Abstract: A consistent set of pair potentials has been derived empirically by fitting to the experimentally measured lattice properties of a series of binary metal oxides. In contrast to previous strategies, the potential parameters required to reproduce the experimental lattice properties of all the chosen compounds were optimised concurrently, utilising residuals from all structures in the series, each calculated from the energy-minimised geometry. A more reliable determination of ion polarisabilities can thus be made.
259 citations
TL;DR: In this paper, the authors describe the preparation and characterisation of colloidal dispersions of polypyrrole-silica nanocomposite particles, and they find that both the particle size and the chemical composition depend markedly on the type of chemical oxidant selected for the in situ polymerisation of the pyrrole monomer.
Abstract: We describe the preparation and characterisation of colloidal dispersions of polypyrrole–silica nanocomposite particles. These nanocomposites have been characterised in terms of their particle size and chemical composition by a wide range of experimental techniques, including transmission electron microscopy, disc centrifuge photosedimentometry, photon correlation spectroscopy, elemental microanalyses, thermogravimetry, infrared spectroscopy and dc solid-state conductivity measurements. We find that both the particle size and the chemical composition depend markedly on the type of chemical oxidant selected for the in situ polymerisation of the pyrrole monomer. For example, using the FeCl3 oxidant we obtain polypyrrole–silica particles which contain up to 70 m/m% polypyrrole and have particle diameters in the range 160–320 nm, whereas the (NH4)2S2O8 oxidant yields composite particles which contain only 37–55 m/m% polypyrrole and are ca. 110–180 nm in diameter. In most cases the particle size distributions are reasonably narrow, with standard deviations as low as 13% as measured by disc centrifuge photosedimentometry. We have also investigated the mechanism of formation of these nanocomposite particles by studying: (i) the adsorption of pyrrole monomer from aqueous solution onto colloidal silica; (ii) the adsorption of oxidant [either FeCl3 or (NH4)2S2O8] from aqueous solution onto colloidal silica. These adsorption studies indicate that either the monomer or the oxidant is partially adsorbed onto the silica particles prior to polymerisation in all of our syntheses. Thus, surface polymerisation processes may be important in the formation of these nanocomposite particles.
131 citations
TL;DR: The crystal structure of LiN(CF3SO2)2 has been solved from X-ray powder diffraction data and refined by the Rietveld method as mentioned in this paper.
Abstract: The crystal structure of lithium bis(trifluoromethanesulfonimide)[LiN(CF3SO2)2] has been solved from X-ray powder diffraction data and refined by the Rietveld method. The salt crystallises in the orthorhombic system, space group Pnaa, a= 9.6351(2)A, b= 5.4154(1)A, c= 16.2639(3)A. The anion, previously uncharacterised crystallographically, has two-fold symmetry around the nitrogen atom, with short [1.56(1)A] S—N distances and a large S—N—S angle [129(1)°]. This is consistent with other similar salts and suggests a high degree of double-bond character and delocalisation around N. Li+ is tetrahedrally coordinated by four oxygens from four neighbouring anions.
119 citations
TL;DR: In this article, high-resolution X-ray powder diffraction using synchrotron radiation has been used to determine the unit-cell parameters of some of the n-alkanes within the range C13H28-C60H122.
Abstract: High-resolution X-ray powder diffraction using synchrotron radiation has been used to determine the unit-cell parameters of some of the n-alkanes within the range C13H28–C60H122. These have, in general, been found to conform to the structural patterns predicted by Nyburg and Potworowski (Acta Crystallogr., Sect. B, 1973, 29, 347). Polymorphic behaviour has been observed for the n= even alkanes associated with increasing symmetry from a triclinic structure (space group P1), to a monoclinic structure (space group P21/a) and to an orthorhombic structure (mostly space group Pca21) as the chain length increases. The n-alkanes C38H78,C40H82 and C44H90 were found to crystallize in the polytypic orthorhombic polymorph (space group Pbca) proposed by Boistelle et al.(Acta Crystallogr., Sect. B, 1976, 32, 1240). The n= odd alkanes all conform to an orthorhombic structure (space group Pbcm). A comparative examination of the data, as a function of chain length, suggests the existence of a degree of structural disorder along the crystallographic c-axis for the longer homologues, which implies that incipient chain folding takes place.
117 citations
TL;DR: In this paper, a novel bis(phthalocyaninato)lutetium(III) complexes substituted with long n-alkyl chains have been synthesized, which show three kinds of discotic mesophase (Dhd, Dob.d, and DL).
Abstract: Novel bis(phthalocyaninato)lutetium(III) complexes substituted with long n-alkyl chains have been synthesized. These complexes, 1a–c, show three kinds of discotic mesophase (Dhd, Dob.d, and DL). Also 1a–c display the three primary colours (red, green, blue) of electrochromism in their solutions. The solutions of oxidized species of 1a–c are nearly red, although those of conventional bis(phthalocyaninato)lutetium(III) complexes are orange.
108 citations
TL;DR: In this article, aqueous solution of zinc salts in the presence of ethylenediamine or triethanolamine was used for the analysis of the morphology of ZnO and ZnS powders.
Abstract: ZnO and ZnS powders were prepared from aqueous solutions of zinc salts in the presence of ethylenediamine or triethanolamine. The morphology of the powders was analysed by scanning electron microscopy and infrared spectroscopy. The effect of the experimental conditions upon the size and shape of the particles is described with a special emphasis on the role of the organic ligand.
108 citations
TL;DR: Sulfonated polyaniline (SPAN) was synthesized by sulfonation of PANI base with fuming sulfuric acid as discussed by the authors, which led to ca. 47% sulfonations of an otherwise unchanged polyanile backbone, which was used as a cation insertion material for battery and electrochromic applications.
Abstract: Sulfonated polyaniline (SPAN) was synthesized by sulfonation of polyaniline (PANI) base with fuming sulfuric acid. Thin films were cast from polymer solutions in basic media. The polymer films were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, ultraviolet–visible–near-infrared spectroscopy, scanning electron microscopy (SEM) and cyclic voltammetry. XPS in combination with FTIR showed that the preparation procedure led to ca. 47% sulfonation of an otherwise unchanged polyaniline backbone. The NIR spectra of SPAN films showed a polaron band at higher energies than with polyaniline. This is in agreement with the lower conductivity of SPAN as compared with polyaniline. SEM micrographs of the SPAN films showed a compact globular morphology. Electrodes modified with thin SPAN films exhibited two redox steps, both in aqueous and in non-aqueous electrolytes. The specific charge stored in SPAN films was found to be ca. 37 A h kg–1 in aqueous solution (only the first redox step) and ca. 68 A h kg–1 in non-aqueous media (both redox steps). A practical SPAN–Li battery could have 50% more specific energy than a PANI–Li battery. The optical spectra of SPAN films exhibited bands at 310, 450 and 750 nm, the intensities of which changed during the redox process. The absorption coefficients of SPAN (emeraldine base state) solutions had values of a= 410 at 313 nm and a= 239 at 563 nm. The suitability of SPAN for use as a cation-insertion material for battery and electrochromic applications is discussed.
100 citations
TL;DR: In this article, the synthesis of layered lithium aluminium hydrotalcite-like materials is described along with different anion exchange procedures for the preparation of materials intercalated with chloride, nitrate and vanadate.
Abstract: The synthesis of layered lithium aluminium hydrotalcite-like materials is described along with different anion exchange procedures for the preparation of materials intercalated with chloride, nitrate and vanadate. The products have been characterised using elemental chemical analysis, powder X-ray diffraction, Fourier-transform infrared spectroscopy and thermogravimetric analysis. The matrices are found to be reasonably stable to acid treatment at pH 4.5 for periods of up to 72 h, with anion exchange taking place. Results indicate that total exchange of interlayer carbonate for chloride, nitrate and vanadate may be accomplished. The thermal properties of the materials have been studied: they demonstrate interesting differences in thermal behaviour compared with hydrotalcite.
94 citations
TL;DR: A variety of straight-chain alkynes with extended π-conjugation through benzene, anthracene and thiophene linker units in the backbone, HCC-R′-CCR-R-CC R′CCR as mentioned in this paper, have been synthesized.
Abstract: A variety of straight-chain alkynes with extended π-conjugation through benzene, anthracene and thiophene linker units in the backbone, H—CC—R′—CC—R—CC—R′—CC—H (R =p-C6H4, 9,10-C14H8, 2,5-C4H2S; R′=p-C6H4, p-C6H4-C6H4-p) has been synthesized. The alkynyl chromophores with an anthracene spacer unit are highly emissive in solution with luminescence quantum yields of up to 0.5. The platinum σ-acetylide polymeric complexes of the above ligands show strong absorptions associated with metal-to-alkynyl ligand charge transfer (MLCT) transitions. It is clear that the π-conjugation is maintained through the metal centres and the optical gap for the polymer, [graphic omitted]Pt(PBun3)2-CC-p-C6H4-CC-9,10-C14H8-CC-p-C6H4-CC[graphic omitted]n is lower than for the complexes [graphic omitted]Pt(PBn3)2-CC-R′-CC-R-CC-R′-CC[graphic omitted]n(R =p-C6H4, 2,5-C4H2S; R′=p-C6H4; p-C6H4-C6H4-p).
94 citations
TL;DR: In this paper, the synthesis of nanocomposite materials consisting of organopolymer molecules encapsulated between ultra-thin mixed-metal hydroxide sheets which are propped apart by spacers acting as pillars was reported.
Abstract: Open lamellar systems such as layered double hydroxides (LDHs) can be used to generate new intercalation compounds. We report the synthesis of nanocomposite materials consisting of organopolymer molecules encapsulated between ultra-thin mixed-metal hydroxide sheets which are propped apart by spacers [terephthalate or hexacyanoferrate(II) ions acting as pillars]. The oxidising host matrixes [Cu(1 –x)2+Crx3+(OH)2]·[(C6H4-1,4-(CO2)2)x/22–·nH2O] and [Cu(1 –x)2+Alx3+(OH)2]·[(Fe(CN)6)x/44–·nH2O] were used as hosts for the interlamellar oxidative polymerisation of aniline. The materials were prepared using chimie douce pathways and characterised by conventional physical techniques (XRD, FTIR, TG, DTA), which indicated the presence of polyaniline molecules and the retention of the host framework after incorporation of the organopolymer.
TL;DR: In this paper, the thermoelectric properties of mixed oxides at high temperature were investigated in terms of their power factor and Seebeck coefficient, and the results showed that the electrical conductivities of these oxides are significantly high.
Abstract: Thethermoelectric properties of mixed oxides In2O3·MOx(MOx= Cr2O3, Mn2O3, NiO, ZnO, Y2O3, Nb2O5 SnO2) are investigated in terms of the thermoelectric materials at high temperature. The Seebeck coefficients,S, of all the samples have negative values, and those of In2O3·SnO2 and In2O3·ZnO increase linearly with temperature, attaining values of –90 and –210 µV K–1 at 1000 °C, respectively. The electrical conductivities, σ, of these oxides are significantly high. The power factor S2σ of the oxides has constantly positive temperature coefficients up to over 1000 °C. Rather low thermal conductivities, κ, of the sintered bodies of the oxides,ca. 1.7 W m–1 K–1 at room temperature, lead to the largest value of the thermoelectric figure of merit Z= 0.4 × 10–4 K–1 for M = Sn at 1000 °C, and the Z value increases toward higher temperatures.
TL;DR: The red luminescence of bismuth-doped alkaline-earth-metal sulfates was attributed to the presence of divalent bistuth in the 6p shell as mentioned in this paper.
Abstract: The red luminescence of bismuth-doped alkaline-earth-metal sulfates is ascribed to the presence of divalent bismuth The optical transitions are due to transitions within the 6p shell.
TL;DR: In this article, the number and strength of the acid centres of tungstic heteropolyacids have been determined by absorption calorimetry of ammonia, and the influence of activation temperature on acidity has been studied and confirms that there is a drastic modification of the solid at ca. 350 °C.
Abstract: The number and strength of the acid centres of tungstic heteropolyacids have been determined by absorption calorimetry of ammonia. The initial heats are in the order H3PW12O40>H4SiW12O40>H6P2W21O71(H2O)3>H6P2W18O62, varying from 200 to 155kJ mol–1. An increase in the number of protons in Keggin heteropolyanions decreases the acidic strength. Moreover, the influence of the activation temperature on the acidity has been studied and confirms that there is a drastic modification of the solid at ca. 350 °C. The heat capacities of the heteropolyanions and of the corresponding ammonium salts, the thermokinetic parameters of ammonia absorption and the heat capacities of the acids and ammonium salts have been related to the porosity of the various samples.
TL;DR: In this paper, a new 13.2 A[d(001)] layered Ti phosphate has been synthesized by using microwave-hydrothermal processing to increase the kinetics of the synthesis of technologically important layered and network phosphates.
Abstract: Novel microwave–hydrothermal processing was used to increase the kinetics of the synthesis of technologically important layered and network phosphates by one to two orders of magnitude. The new powder processing technique, which is ‘environmentally benign’, appears to favour the formation of layered phases. A new 13.2 A[d(001)] layered Ti phosphate has been synthesized by this technique. This phase shows high caesium exchange selectivity and it may be useful for separation of radioactive Cs from acidic nuclear wastes and in decontamination of the environment after accidental releases of Cs.
TL;DR: A number of liquid-crystalline siloxane derivatives based on the 4-(alkenyloxy)-4′-cyanobiphenyl mesogenic unit have been prepared and their phase-transitional properties characterised as discussed by the authors.
Abstract: A number of liquid-crystalline siloxane derivatives based on the 4-(ω-alkenyloxy)-4′-cyanobiphenyl mesogenic unit have been prepared and their phase-transitional properties characterised. The compounds were synthesized by the addition of the 4-(ω-alkenyloxy)-4′-cyanobiphenyl moiety to pentamethyldisiloxane catalysed by a platinum divinyltetramethyldisiloxane complex. The materials are denoted ABs where A refers to the number of methylene groups in the 4-(ω-alkenyloxy)-4′-cyanobiphenyl and B refers to the number of silicon atoms in the siloxane unit. With the exception of 3/2 and 4/2, which exhibit only monotropic phase transitions, all these materials exhibit an enantiotropic smectic A phase. Preliminary X-ray results also support this. The thermal properties of this new series of thermotropic liquid-crystalline siloxanes were studied by differential scanning calorimetry (DSC) and polarising microscopy. The transitional properties for the AB series exhibit a pronounced odd–even effect with the length of the alkyl segment.
TL;DR: In this paper, the structure and energies of the low-index surfaces of spinel (MgAl2O4) using atomistic simulation techniques were investigated and the results illustrate the complexity of modelling the surfaces of ternary oxides, particularly since cation ordering, resulting in the formation of inverse spinel, plays a crucial role in determining the relative surface stability.
Abstract: We present the results from a recent study of the structure and energies of the low-index surfaces of spinel (MgAl2O4) using atomistic simulation techniques. These illustrate the complexity of modelling the surfaces of ternary oxides, particularly since cation ordering, resulting in the formation of inverse spinel, plays a crucial role in determining the relative surface stability. The simulations show some agreement with the very limited experimental data available for the spinel class of compounds. However, agreement with the most common experimental morphologies requires the consideration of kinetic factors.
TL;DR: In this article, thin films of ZnO have been grown by low-pressure MOCVD using methylzinc isopropoxide, MeZn(OPri), and MeZinc tert-butoxide (MeZn) in the absence of an added oxygen source.
Abstract: Thin films of ZnO have been grown by low-pressure MOCVD using methylzinc isopropoxide, MeZn(OPri), and methylzinc tert-butoxide, MeZn(OBut), in the absence of an added oxygen source. The films were grown on to glass substrates in the temperature range 250–400 °C with growth rates of between 0.2 and 4.4 µm h–1.
TL;DR: In this article, the authors describe both the methodologies and recent applications of atomistic computer modelling techniques in materials chemistry and illustrate the range of contemporary applications of modelling methods by accounts of recent work on the simulation of the structures of crystalline and amorphous solids, on the structures and properties of surfaces and interfaces, and on the dynamics of ions in solids.
Abstract: We describe both the methodologies and recent applications of atomistic computer modelling techniques in materials chemistry. We discuss first, simulation techniques based on interatomic potentials, where we review the scope of static lattice methods (applied to both perfect and defective crystal structures), molecular dynamics and Monte Carlo techniques. The role of electronic structure methods based on both Hartree–Fock and local density functional methods is then reviewed including reference to periodic boundary conditions and embedded cluster calculations. We illustrate the range of contemporary applications of modelling methods by accounts of recent work on the simulation of the structures of crystalline and amorphous solids, on the structures and properties of surfaces and interfaces, on the dynamics of ions in solids and, finally, on the challenging problems posed by the development and understanding of catalytic processes.
TL;DR: In this paper, the properties of 20 structurally related octa-substituted phthalocyanine derivatives have been assessed by visible-region spectroscopy and low-angle X-ray diffraction methods.
Abstract: The monolayer and LB film-forming properties of 20 structurally related amphiphilic octa-substituted phthalocyanine derivatives have been assessed. The molecular packing within examples of the films has been probed by visible-region spectroscopy and low-angle X-ray diffraction methods. Among derivatives where the aliphatic substituents are attached by ether linkages, there is a variation in the behaviour according to the length of the chains and whether or not the chains are branched. Films are not highly ordered but may contain domains of ordered structure, giving rise to a red-shifted absorption band in the visible spectrum. Analogues where the chains are attached by carbon–carbon bonds show superior monolayer behaviour and are excellent materials for deposition as LB films. Furthermore, there is good evidence from the spectra that change in the length of the alkyl chains provides a means of controlling the type of molecular packing within the films.
Abstract: The synthesis of tetra[oligo(ethyleneoxy)]phthalocyanines is described. Preliminary characterization of both thermotropic and lyotropic mesophases obtained from examples of this series are reported.
TL;DR: In this paper, a magnesium-manganese hydroxycarbonate with the hydrotalcite structure was synthesized by coprecipitation from aqueous solutions of Mg2+ and Mn2+.
Abstract: A magnesium–manganese hydroxycarbonate with the hydrotalcite structure has been synthesized by coprecipitation from aqueous solutions of Mg2+ and Mn2+. According to temperature-programmed reduction data, 84% of the manganese is oxidized to Mn3+ during synthesis. Fourier-transform infrared spectroscopy, powder X-ray diffraction and transmission electron microscopy data support the hydrotalcite structure. Thermal decomposition in air at 390 °C leads to an amorphous material with a simultaneous increase of the specific surface area. Further calcination at higher temperatures (670 and 1000 °C) leads to crystallization of MgO and Mg2MnO4 spinel and to sintering. Reduction of the spinel takes place in two separate steps, probably through formation of intermediate Mn3O4 and finally MnO.
TL;DR: In this paper, the ternary sulfides form thin, mostly coloured plates and are characterized by powder X-ray diffraction, scanning electron microscopy (SEM), energy dispersive analysis by X-rays (EDXA), Raman, infrared, magnetic moments and microanalysis.
Abstract: Ternary alkali-metal–rare-earth-metal sulfides, MRES2(M = Li, Na, K; RE = Y, La–Yb) were prepared by heating RECL3and M2S under an H2S–N2 atmosphere at 750–800 °C for 10 min. The ternary sulfides form thin, mostly coloured plates. The structures were characterised by X-ray powder diffraction, which revealed high-temperature cubic modifications for LiHoS2 and LiErS2. The disordered cubic form (NaCl type) was observed for LiLnS2(Ln = Pr–Er) and NaLnS2(Ln = La–Nd), while the ordered rhombohedral form (α-NaFeO2 type) was observed for LiYbS2, NaLnS2(Sm–Yb) and KLnS2(La–Yb). Alkali-metal–rare-earth-metal sulfides may also be synthesized from the rare-earth-metal chloride and alkali-metal halide under comparable conditions. Similarly, thermolysis of the rare-earth-metal sesquisulfide (γ-RE2S3), oxysulfide (RE2O2S) or oxychloride (REOCL) with M2S or MCI in an atmosphere of H2S-N2 gives MRES2. The materials were characterised by powder X-ray diffraction, scanning electron microscopy (SEM), energy dispersive analysis by X-rays (EDXA), Raman, infrared, magnetic moments and microanalysis.
TL;DR: In this article, a series of poly(methacrylate)-based side-chain liquid crystal polymers, the poly[ω-(4′-methoxybiphenyl-4-yloxy)alkyl methacrylated]s, have been synthesized in which the spacer length is varied from 3 to 12 methylene units.
Abstract: A series of side-chain liquid crystal polymers, the poly[ω-(4′-methoxybiphenyl-4-yloxy)alkyl methacrylate]s, have been synthesized in which the spacer length is varied from 3 to 12 methylene units. This is the first example of a poly(methacrylate)-based side-chain liquid crystal polymer series for which as many as 10 homologues have been prepared. The thermal properties have been characterised using differential scanning calorimetry and polarised light microscopy. All 10 homologues exhibit smectic behaviour; in addition, the butyl homologue is nematogenic. The clearing temperatures and associated entropy changes exhibit a distinct odd–even effect as the length and parity of the spacer is varied with the odd members exhibiting the higher values. This behaviour is rationalised in terms of the change in the average shape of the side chain on varying the parity of the spacer. The properties of the polymers are compared to those containing the same mesogenic group but different polymer backbones in order to consider the effect of flexibility on thermal behaviour. In general, these comparisons support the view that increasing backbone flexibility enhances the clearing transition while tending to decrease the entropy change associated with the transition. Exceptions to this rule are rationalised either in terms of molecular weight dependent effects or in the case of poly(norbornene)-based materials, are thought to arise from the complex microstructure of the polymer chains. Replacing the alkyl spacer by an oligo(ethylene oxide) chain reduces the clearing transition of the polymer. This is rationalised in terms of the flexibility and preferred conformations of an oligo(ethylene oxide) spacer.
TL;DR: In this article, the mild treatment of various zeolites (X, Y and ZSM-5) with sodium carbonate in aqueous solutions has been investigated, and the removal of silicon from highly siliceous zeolite led to a significant decrease of the Si : Al ratio.
Abstract: The mild treatment of various zeolites (X, Y and ZSM-5) with sodium carbonate in aqueous solutions has been investigated. The removal of silicon from highly siliceous zeolites led to a significant decrease of the Si : Al ratio, mostly with the ZSM-5 and Y zeolites. However, the original structure, surface area and size of the micropores were essentially preserved, although healing processes did occur after silicon removal from the framework. All the aluminium atoms remained in the tetrahedral configuration during the treatment, which, therefore, provides a novel means for significantly increasing the ion–exchange capacity or the density of protonic sites of the zeolites studied.
TL;DR: In this paper, a series of copper complexes of epoxy-imidazole adducts have been prepared and characterized by 1H nuclear magnetic resonance (NMR) spectroscopy.
Abstract: A series of copper complexes of epoxy-imidazole adducts have been prepared and characterized by 1H nuclear magnetic resonance (NMR) spectroscopy. Differential scanning calorimetry (DSC) was employed to investigate the thermal behaviour of the curing agents and to investigate the medium-term storage stability of a one-pot composition of a commercial epoxy resin when mixed with the complexes. The cure onset temperatures of the mixtures containing copper complexes are ca. 20–50 °C higher than those of the parent epoxy-imidazole adducts and the decrease of cure onset temperatures in the early stages of storage (up to 100 h) is less. The latent nature and improved storage stability of mixtures containing the copper complex were clearly demonstrated and confirmed by the viscosity behaviour of the catalysed mixtures of the commercial epoxy resins MY720 and MY750. 1H NMR and electron paramagnetic resonance (EPR) spectroscopy were employed to monitor the thermal decomposition of the copper(II) complexes, which were found to decompose at 120–130 °C and exist in equilibrium. Glass fibre-reinforced composite samples were prepared using a commercial epoxy resin cured with the complexes and their physico-mechanical properties were evaluated.
TL;DR: In this paper, the electrogeneration of base from the cathodic reduction of metal salt solutions such as nitrate or perchlorate is described as a soft chemical route to the preparation of thin films of hydroxides.
Abstract: Electrodeposition of several unary and layered double hydroxides has been achieved by electrogeneration of base from the cathodic reduction of metal salt solutions such as nitrate or perchlorate. This simple one-step preparation can be adapted as a soft chemical route to the preparation of thin films of hydroxides.
TL;DR: Sulfonated indolinespirobenzopyran (SP-SO3-) was intercalated into the Mg/Al or Zn/Al layered double hydroxides (LDHs) in the presence of toluene-p-sulfonic acid (PTS) as mentioned in this paper.
Abstract: Sulfonated indolinespirobenzopyran (SP–SO3–) was intercalated into the Mg/Al or Zn/Al layered double hydroxides (LDHs) in the presence of toluene-p-sulfonic acid (PTS). The new intercalates exhibited reversible photoisomerization between SP–SO3– and merocyanine (MC). The presence of PTS was critical for the reversible photoisomerization. MC was very stable and the rate constant of decolorization was <9 × 10–7S–1. SP interacted with non-polar portions between the layers although MC interacted with the polar interior surface of the LDH.
TL;DR: In this paper, the steric hindrance groups, 2-ethylhexyl (b) and 4-octadecyloxyphenyl (d), tend to induce the appearance of the Dtet.d phase.
Abstract: Phthalocyanine compounds substituted with steric hindrance groups have been synthesized: octakis(2-ethyl-hexyl)phthalocyanine (1b) and bis[octakis(4-octadecyloxyphenyl)phthalocyaninato]lutetium(III) complex (2d). These compounds exhibit a wide temperature range of discotic liquid-crystalline properties. Each of these compounds shows a discotic tetragonal disordered columnar mesophase (Dtet.d) or a discotic plain rectangular disordered columnar mesophase [Drd(p2m)] with a lattice very close to tetragonal. This Drd(p2m) phase is a novel discotic mesophase that has not been reported to date. It was found that the introduction of the steric hindrance groups, 2-ethylhexyl (b) and 4-octadecyloxyphenyl (d), tend to induce the appearance of the Dtet.d phase.
TL;DR: The crystal structure of NaY(MoO4)2 was determined from powder X-ray diffraction data [space group I41/a, Z= 2, a= 5.19890(5)A, c= 11.3299(1)A] and found to be scheelite related, with the tetrahedral sites occupied by, an ordered arrangement of Mo and Na in a 4 : 1 ratio.
Abstract: The crystal structure of NaY(MoO4)2 has been determined from powder X-ray diffraction data [space group I41/a, Z= 2, a= 5.19890(5)A, c= 11.3299(1)A]. The Na and Y atoms are disordered over the eight-coordinate sites of a scheelite structure. The crystal structure of Na5Y(MoO4)4 has been determined from single-crystal X-ray diffraction data [space group I41/a, Z= 4, a= 11.374(3)A, c= 11.440(5)A] and found to be scheelite related, with the tetrahedral sites occupied by, an ordered arrangement of Mo and Na in a 4 : 1 ratio. Comparisons are drawn between the structures of these two closely related phosphor materials.