Protic ionic liquids based on the dimeric and oligomeric anions: [(AcO)xH(x-1)]-

We describe a fluidity and conductivity study as a function of composition in N-methylpyrrolidine-acetic acid mixtures. The simple 1 : 1 acid-base mixture appears to form an ionic liquid, but its degree of ionicity is quite low and such liquids are better thought of as poorly dissociated mixtures of acid and base. The composition consisting of 3 moles acetic acid and 1 mole N-methylpyrrolidine is shown to form the highest ionicity mixture in this binary due to the presence of oligomeric anionic species [(AcO)(x)H(x-1)](-) stabilised by hydrogen bonds. These oligomeric species, being weaker bases than the acetate anion, shift the proton transfer equilibrium towards formation of ionic species, thus generating a higher degree of ionicity than is present at the 1 : 1 composition. A Walden plot analysis, thermogravimetric behaviour and proton NMR data, as well as ab initio calculations of the oligomeric species, all support this conclusion.     

Influence of flame retardant additives on the processing characteristics and physical properties of ABS

Antimony trioxide (Sb₂O₃) is a common additive in flame retardant formulations and a study has been made to determine the effects of adding different grades into ABS polymer either alone or with commercial brominated materials bis(Tribromophenoxy)ethane (BTBPE) or Tetrabromobisphenol A (TBBA). The results consider mechanical, microscopical and flame retardant properties, and the effects of different Sb₂O₃ grades with average particle sizes of 0.1μm, 0.52μm and 1.31μm. The Sb₂O₃ was added at 4wt% loadings and the bromines at 20wt% loadings. Additions of different grades of antimony trioxide showed that standard grades (0.52 and 1.31μm) had a detrimental effect on impact and flexural properties when added at a 4wt% loading. The use of a new sub‐micron particle size product (0.1μm) had little effect on impact properties and only a slight detrimental effect on the flexural modulus and flexural strength when added to the ABS. Additions of either of the two brominated materials also caused a large drop in impact properties when added at 20wt% loadings. The addition of TBBA BA‐59P into ABS caused an increase in both flexural modulus and flexural strength which was contrary to expectations. When formulated with 4wt% 1.31μm Sb₂O₃ these bromine containing compounds suffered a further reduction in impact energies. Using the 0.1μm material improved both impact and flexural properties but impact values were still below those of unfilled ABS. The addition of the 0.1μm grade resulted in improvements in fire resistance as measured by the UL‐94 properties.     

Chlorometallate(III) ionic liquids as Lewis acidic catalysts--a quantitative study of acceptor properties

The Gutmann Acceptor Number (AN), which is a quantitative measure of Lewis acidity, has been estimated using the (31)P NMR chemical shift of a probe molecule, triethylphosphine oxide, for a range of chlorometallate(III) ionic liquids, based on Group 13 metals (aluminium(III), gallium(III) and indium(III)) and the 1-octyl-3-methylimidazolium cation, at different compositions. The results were interpreted in terms of extant speciation studies of chlorometallate(III) ionic liquids, and compared with a range of standard molecular solvents and acids. The value of these data were illustrated in terms of the selection of appropriate ionic liquids for specific applications.     

Mutually immiscible ionic liquids

This work presents the novel discovery of room-temperature ionic liquids that are mutually immiscible, some of which are also immiscible with solvents as diverse as water and alkanes; an archetypal biphasic system is trihexyltetradecylphosphonium chloride with 1-alkyl-3-methylimidazolium chloride (where the alkyl group is shorter than hexyl).     

A structural and electrochemical investigation of 1-alkyl-3-methylimidazolium salts of the nitratodioxouranate(VI) anions [[UO2(NO3)2]2(mu 4-C2O4)]2-, [UO2(NO3)3]-, and [UO2(NO3)4]2-

The properties of the 1-butyl-3-methylimidazolium salt of the dinuclear mu(4)-(O,O,O',O'-ethane-1,2-dioato)bis[bis(nitrato-O,O)dioxouranate(VI)] anion have been investigated using electrochemistry, single-crystal X-ray crystallography, and extended X-ray absorbance fine structure spectroscopy: the anion structures from these last two techniques are in excellent agreement with each other. Electrochemical reduction of the complex leads to the a two-electron metal-centered reduction of U(VI) to U(IV), and the production of UO(2), or a complex containing UO(2). Under normal conditions, this leads to the coating of the electrode with a passivating film. The presence of volatile organic compounds in the ionic liquids 1-alkyl-3-methylimidazolium nitrate (where the 1-alkyl chain was methyl, ethyl, propyl, butyl, pentyl, hexyl, dodecyl, hexadecyl, or octadecyl) during the oxidative dissolution of uranium(IV) oxide led to the formation of a yellow precipitate. To understand the effect of the cation upon the composition and structure of the precipitates, 1-alkyl-3-methylimidazolium salts of a number of nitratodioxouranate(VI) complexes were synthesized and then analyzed using X-ray crystallography. It was demonstrated that the length of the 1-alkyl chain played an important role, not only in the composition of the complex salt, but also in the synthesis of dinuclear anions containing the bridging mu(4)-(O,O,O',O'-ethane-1,2-dioato), or oxalato, ligand, by protecting it from further oxidation.     

Accurate Modelling of Liquid Crystal-Based Microwave Devices

Liquid crystal substrates have been shown to provide the means to develop low-cost, reconfigurable, adaptive and tuneable microwave devices for mobile and wireless communication systems. In order to take maximum advantage of the possibilities that these materials offer and to design LC-based devices appropriately, techniques for the characterisation of the liquid crystal dielectric properties are needed. Similarly, appropriate modelling methods are required to simulate accurately the switching behaviour of the liquid crystal and the characteristics of the wave propagation through the devices, taking full consideration of the point-by-point variation of the material tensor permittivity.     

Calculations of and evidence for chain packing stress in inverse lyotropic bicontinuous cubic phases

Inverse bicontinuous cubic lyotropic phases are a complex solution to the dilemma faced by all self-assembled water-amphiphile systems: how to satisfy the incompatible requirements for uniform interfacial curvature and uniform molecular packing. The solution reached in this case is for the water-amphiphile interfaces to deform hyperbolically onto triply periodic minimal surfaces. We have previously suggested that although the molecular packing in these structures is rather uniform the relative phase behavior of the gyroid, double diamond, and primitive inverse bicontinuous cubic phases can be understood in terms of subtle differences in packing frustration. In this work, we have calculated the packing frustration for these cubics under the constraint that their interfaces have constant mean curvature. We find that the relative packing stress does indeed differ between phases. The gyroid cubic has the least packing stress, and at low water volume fraction, the primitive cubic has the greatest packing stress. However, at very high water volume fraction, the double diamond cubic becomes the structure with the greatest packing stress. We have tested the model in two ways. For a system with a double diamond cubic phase in excess water, the addition of a hydrophobe may release packing frustration and preferentially stabilize the primitive cubic, since this has previously been shown to have lower curvature elastic energy. We have confirmed this prediction by adding the long chain alkane tricosane to 1-monoolein in excess water. The model also predicts that if one were able to hydrate the double diamond cubic to high water volume fractions, one should destabilize the phase with respect to the primitive cubic. We have found that such highly swollen metastable bicontinuous cubic phases can be formed within onion vesicles. Data from monoelaidin in excess water display a well-defined transition, with the primitive cubic appearing above a water volume fraction of 0.75. Both of these results lend support to the proposition that differences in the packing frustration between inverse bicontinuous cubic phases play a pivotal role in their relative phase stability.     

Electronic and surface properties of PbS nanoparticles exhibiting efficient multiple exciton generation

Ultrafast transient absorption measurements have been used to study multiple exciton generation in solutions of PbS nanoparticles vigorously stirred to avoid the effects of photocharging. The threshold and slope efficiency of multiple exciton generation are found to be 2.5 ± 0.2 ×E(g) and 0.34 ± 0.08, respectively. Photoemission measurements as a function of nanoparticle size and ageing show that the position of the valence band maximum is pinned by surface effects, and that a thick layer of surface oxide is rapidly formed at the nanoparticle surfaces on exposure to air.     

Working group report: Heavy-ion physics and quark-gluon plasma

This is the report of Heavy Ion Physics and Quark-Gluon Plasma at WHEPP-09 which was part of Working Group-4. Discussion and work on some aspects of quark-gluon plasma believed to have created in heavy-ion collisions and in early Universe are reported.