The influence of different nanoparticles on a range of organic ionic plastic crystals

The addition of nanoparticles to an organic ionic plastic crystal can result in orders of magnitude increases in ionic conductivity, which makes these materials of interest as solid state electrolytes. However, this effect is not universal and depends on both the nature of the organic ionic plastic crystal and on the type of nanoparticle used. The effect of addition of TiO₂, Al₂O₃ and SiO₂ nanoparticles to a range of ionic materials with varying plasticity and rotator phase behaviour has been studied by thermal analysis and conductivity and the effect on the different materials is compared.

High pressure measurements of the refractive indices of two nematic liquid crystals

The refractive indices of two nematogens, 4-methoxy-benzylidene-4 prime -n-butylaniline (MBBA) and 4-n-pentyl-4 prime -cyanobiphenyl (5CB), were measured throughout their nematic ranges at pressures up to 2 kbar and temperatures up to 70 degree C in the first substance and up to 5 kbar and 145 degree C in the second. Measurements were made at lambda equals 5,890 A, using a sensitive interference fringe technique. Results are presented in the form of functions n//e(P, T) for the extraordinary index and n//o (P, T) for the ordinary index, obtained by least squares fits to the experimental data.

Refractive indices and order parameters of two liquid crystals

Refractive indices have been measured throughout the nematic phase of 4-n-pentyl-4'cyanobiphenyl (5CB) and the smectic A and nematic phases of 4-n-octyl-4'-cyanobiphenyl (8CB). The Vuks and Neugebauer methods of calculating the order parameter are compared. Without knowledge of the molecular polarisabilities it is only possible to calculate a quantity proportional to the order parameter, and within this limitation it is found that the two methods give identical results. The order parameter is scaled using the extrapolation method suggested by Haller [14]. Using a suitable average of the refractive indices and the density data of Gannon and Faber [9], it is shown that the Lorentz-Lorenz relation is obeyed over a 2 % density range in 5CB.

Direct measurement of surface forces between sapphire crystals in aqueous solutions

Measurements are presented of the electrical double layer and van der Waals forces between the (0001) surfaces of two single-crystal sapphire platelets immersed in an aqueous solution of NaCl at pH values from 6.7 to 11. The results fit the standard Deryaguin-Landau-Verwey-Overbeek (DLVO) theory, with a Hamaker constant of 6.7 × 10−20 J. These are the first measurements made using the Israelachvili surface forces apparatus without mica as a substrate material, and they demonstrate the possibility of using this technique to explore the surface chemistry of a wider range of materials.

Molecular alignment in nematic liquid crystals : a comparison between the results of experiments at high pressure and predictions based on mean field theories

The effects of high pressure on molecular arrangment in liquid crystals were observed by optical measurements on two nematogens. It was possible to deduce how volume varies as a factor of temperature and pressure and how nematic order parameter changes under the influence of high pressure.

Ionic liquids and organic ionic plastic crystals utilizing small phosphonium cations

The development of new liquid and solid state electrolytes is paramount for the advancement of electrochemical devices such as lithium batteries and solar cells. Ionic liquids have shown great promise in both these applications. Here we demonstrate the use of phosphonium cations with small alkyl chain substituents, in combination with a range of different anions, to produce a variety of new halide free ionic liquids that are fluid, conductive and with sufficient thermal stability for a range of electrochemical applications. Walden plot analysis of the new phosphonium ionic liquids shows that these can be classed as "good" ionic liquids, with low degrees of ion pairing and/or aggregation, and the lithium deposition and stripping from one of these ionic liquids has been demonstrated. Furthermore, for the first time phosphonium cations have been used to form a range of organic ionic plastic crystals. These materials can show significant ionic conductivity in the solid state and thus are of great interest as potential solid-state electrolyte materials.

Effects of crystallographic orientation on corrosion behavior of magnesium single crystals

The corrosion behavior of magnesium single crystals with various crystallographic orientations was examined in this study. To identify the effects of surface orientation on the corrosion behavior in a systematic manner, single-crystal specimens with ten different rotation angles of the plane normal from the [0001] direction to the [1010] direction at intervals of 10° were prepared and subjected to potentiodynamic polarization and potentiostatic tests as well as electrochemical impedance spectroscopy (EIS) measurements in 3.5 wt.% NaCl solution. Potentiodynamic polarization results showed that the pitting potential (E _pit) first decreased from −1.57 V _SCE to −1.64 V _SCE with an increase in the rotation angle from 0° to 40°, and then increased to −1.60 V _SCE with a further increase in the rotation angle to 90°. The results obtained from potentiostatic tests are also in agreement with the trend in potentiodynamic polarization tests as a function of rotation angle. A similar trend was also observed for the depressed semicircle and the total resistances in the EIS measurements due to the facile formation of MgO and Mg(OH)₂ passive films on the magnesium surface. In addition, the amount of chloride in the passive film was found first to increase with an increase in rotation angle from 0° to 40°, then decrease with a further increase in rotation angle, indicating that the tendency to form a more protective passive film increased for rotation angle near 0° [the (0001) plane] or 90° [the (1010) plane].

Halogen-free chelated orthoborate ionic liquids and organic ionic plastic crystals

Five halogen-free orthoborate salts comprised of three different cations (cholinium, pyrrolidinium and imidazolium) and two orthoborate anions, bis(mandelato)borate and bis(salicylato)borate, were synthesised and characterised by DSC, X-ray diffraction and NMR. DSC measurements revealed that glass transition points of these orthoborate salts are in the temperature range from −18 to −2 °C. In addition, it was found that [EMPy][BScB] and [EMIm][BScB] salts have solid–solid phase transitions below their melting points, i.e. they exhibit typical features of plastic crystals. Salts of the bis(salicylato)borate anion [BScB]− have higher melting points compared with corresponding salts of the bis(mandelato)borate anion [BMB]−. Single crystal X-ray diffraction crystallography (for [Chol][BScB] crystals) and solid-state multinuclear (13C, 11B and 15N) NMR spectroscopy were employed for the structural characterisation of [Chol][BScB], [EMPy][BScB] and [EMIm][BScB], which are solids at room temperature: a strong interaction between [BScB]− anions and [Chol]+ cations was identified as (i) hydrogen bonding between OH of [Chol]+ and carbonyl groups of [BScB]− and (ii) as the inductive C–Hπ interaction. In the other salt, [EMIm][BScB], anions exhibit ππ stacking in combination with C–Hπ interactions with [EMIm]+ cations. These interactions were not identified in [EMPy][BScB] probably because of the lack of aromaticity in cations of the latter system. Our data on the formation of a lanthanum complex with bis(salicylato)borate in the liquid mixture of La3+(aq) with [Chol][BScB] suggest that this class of novel ILs can be potentially used in the extraction processes of metal ions of rare earth elements.

Polymeric materials with ordered nanostructures templated from hexagonal lyotropic liquid crystals

In this study, successful methods have been established to retain the ordered nanostructures in polymer materials templated from hexagonal lyotropic liquid crystals, which potentially renders broad applications as biomedical and membrane materials.

Organic Solvent-Based Graphene Oxide Liquid Crystals: A Facile Route toward the Next Generation of Self-Assembled Layer-by-Layer Multifunctional 3D Architectures

We introduce soft self-assembly of ultralarge liquid crystalline (LC) graphene oxide (GO) sheets in a wide range of organic solvents overcoming the practical limitations imposed on LC GO processing in water. This expands the number of known solvents which can support amphiphilic self-assembly to ethanol, acetone, tetrahydrofuran, N-dimethylformamide, N-cyclohexyl-2-pyrrolidone, and a number of other organic solvents, many of which were not known to afford solvophobic self-assembly prior to this report. The LC behavior of the as-prepared GO sheets in organic solvents has enabled us to disperse and organize substantial amounts of aggregate-free single-walled carbon nanotubes (SWNTs, up to 10 wt %) without compromise in LC properties. The as-prepared LC GO-SWNT dispersions were employed to achieve self-assembled layer-by-layer multifunctional 3D hybrid architectures comprising SWNTs and GO with unrivalled superior mechanical properties (Young’s modulus in excess of 50 GPa and tensile strength of more than 500 MPa).

Phase behaviour and properties of microemulsions and lyotropic liquid crystals

This research study has developed new ways to control bulk properties of self-assembled microemulsions and lyotropic liquid crystals (LLCs) by manipulations of their corresponding precursor phase behaviour. Investigation into relating phase behaviour with the morphology, porosity, thermal stability, rheological property, and photoresponse of these assemblies has been carried out.