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Permanent URI for this collectionhttp://ir-dev.dut.ac.za/handle/10321/213

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Author: search.filters.author.Deenadayalu, NirmalaSubject: search.filters.subject.Ionic liquids

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    The influence of various alkylammonium-based ionic liquids on the hydration state of temperature-responsive polymer
    (Elsevier, 2016-11-19) Umapathi, Reddicherla; Mhkize, Thandeka Yvonne; Venkatesu, Pannuru; Deenadayalu, Nirmala
    The influence of different alkylammonium-based ionic liquids (ILs) on the temperature-dependent aqueous poly(N-isopropylacrylamide) (PNIPAM) solution is explored by the comprehensive experimental analysis. The co-solvents investigated in the present study included a series of ILs with a fixed (trifluromethylsulfonyl)imide [NTf2]− anion and variable ammonium cations such as butyltrimethylammonium (IL-1), methyl-trioctylammonium (IL-2), diethylmethyl(2-methoxyethyl)ammonium (IL-3) and ethyldimethylpropyla mmonium (IL-4). The thermal phase transitions of aqueous solution of thermo-responsive polymer (TRP) in ammonium-based ILs were studied by various experimental techniques such as fluorescence spectroscopy, dy-namic light scattering (DLS) and viscosity (η). We further employed field emission scanning electron microscope (FESEM) to reveal the distinct morphological changes of various self-assembled morphologies. Our results reveal that the lower critical solution temperature (LCST) of the TRP can be significantly altered by the ILs. The phase transition state of aqueous TRP decreases as the concentration of IL increased. We find that IL-4 lowers the LCST of TRP significantly more as compared to the other ILs. Our experimental results reveal that the hydrophobic interactions are predominant between the monomers of PNIPAM and ions of the ILs. This research work high-lights new opportunities for the wide applications in engineering of the bio-responsive smart PNIPAM-based de-vices and appropriate selection of ILs, which should allow for increasing the usage of thermo-responsive phase behaviour of polymers.
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    Densities, speeds of sound, and refractive indices for binary mixtures of 1-butyl-3-methylimidazolium methyl sulphate ionic liquid with alcohols at T = (298.15, 303.15, 308.15, and 313.15) K
    (Elsevier, 2012-09-24) Singh, Sangeeta; Aznar, Martin; Deenadayalu, Nirmala
    Experimental densities, speeds of sound, and refractive indices of the binary mixtures {1-butyl-3-methylimidazolium methylsulphate ([BMIM]+[MeSO4]−) + methanol, or 1-propanol, or 2-propanol, or 1-butanol} were measured over the whole range of composition at T = (298.15, 303.15, 308.15, and 313.15) K. From the experimental data, excess molar volumes, excess isentropic compressibilities, deviation in refractive indices and molar refractions were calculated. The excess molar volumes, change in isentropic compressibilities, and deviation in refractive indices were fitted by the Redlich–Kister smoothing polynomial. The Lorentz–Lorenz equation was applied to correlate the volumetric properties and predict the density or the refractive index of the binary mixtures. Results for these quantities have been discussed in terms of intermolecular interactions between the components of the mixtures. For all the systems studied, the excess molar volume and excess isentropic compressibility are negative, while the change in refractive index on mixing is always positive over the entire composition range and at all temperatures.