Browsing by Author "Atkin, R"

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    Phase behaviour and aggregate structures of the surface-active ionic liquid [BMIm][AOT] in water
    (Elsevier B.V., 2023-12-15) Zhang, YX; Marlow, JB; Wood, K; Wang, J; Warr, GG; Li, H; Atkin, R
    Hypothesis: The surface-active ionic liquid, 1-butyl-3-methylimidazolium 1,4-bis-2-ethylhexylsulfosuccinate ([BMIm][AOT]), has a sponge-like bulk nanostructure consisting of percolating polar and apolar domains formed by the ion charge groups and alkyl chains, respectively. We hypothesise that added water will swell the polar domains and change the liquid nanostructure. Experiments: Small angle X-ray scattering (SAXS), small angle neutron scattering (SANS) and polarizing optical microscopy (POM) were used to investigate the nanostructure of [BMIm][AOT] as a function of water content. Differential scanning calorimetry (DSC) was employed to probe the thermal transitions of [BMIm][AOT]-water mixtures and the mobility of water molecules. Findings: SAXS, SANS and POM show that at lower water contents, [BMIm][AOT]-water mixtures have a sponge-like nanostructure similar to the pure SAIL, at medium water contents a lamellar phase forms, and at high water contents vesicles form. DSC results reveal that water molecules are supercooled in the lamellar phase. For the first time, results reveal a series of transitions from inverse sponge, to lamellar then to vesicles, for [BMIm][AOT] upon dilution with water. © 2023 Elsevier Inc.
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    Structure of the ethylammonium nitrate surface: an x-ray reflectivity and vibrational sum frequency spectroscopy study
    (American Chemical Society, 2010-06-01) Niga, P; Wakeham, D; Nelson, A; Warr, GG; Rutland, M; Atkin, R
    X-ray reflectivity and vibrational sum frequency spectroscopy are used to probe the structure of the ethylammonium nitrate (EAN)−air interface. X-ray reflectivity reveals that the EAN−air interface is structured and consists of alternating nonpolar and charged layers that extend 31 Å into the bulk. Vibrational sum frequency spectroscopy reveals interfacial cations have their ethyl moieties oriented toward air, with the CH3 C3 axis positioned 36.5° from interface normal. This structure is invariant between 15 and 51°C. On account of its molecular symmetry, the orientation of the nitrate anion cannot be determined with certainty. © 2010, American Chemical Society