Effect of Cation Symmetry on the Morphology and Physicochemical Properties of Imidazolium Ionic Liquids

Wei Zheng, Ali Mohammed, Jr Larry G. Hines, Dong Xiao, Omar J. Martinez, Richard Bartsch, Sindee Simon, Olga Russina, Alessandro Triolo, Edward Quitevis

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Abstract

In this paper, the morphology and bulk physical properties of 1,3-dialkylimidazolium bis{(trifluoromethane)sulfonyl}amide ([(C-N/2)(2)im][NTf2]) are compared to that of 1-alkyl-3-methylimidazolium bis{(trifluoromethane)sulfonyl}amide ([C(N-1)C(1)im][NTf2]) for N = 4, 6, 8, and 10. For a given pair of ionic liquids (ILs) with the same N, the ILs differ only in the symmetry of the alkyl substitution on the imidazolium ring of the cation. Small-wide-angle X-ray scattering measurements indicate that, for a given symmetric/asymmetric IL pair, the structural heterogeneities are larger in the asymmetric IL than in the symmetric IL. The correlation length of structural heterogeneities for the symmetric and asymmetric salts, however, is described by the same linear equation when plotted versus the single alkyl chain length. Symmetric Its with N = 4 and 6 easily crystallize, whereas longer alkyl chains and asymmetry hinder crystallization. Interestingly, the glass transition temperature is foun
Original languageEnglish
Pages (from-to)6572 - 6584
JournalJournal of Physical Chemistry B
StatePublished - May 26 2011

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Zheng, W., Mohammed, A., Larry G. Hines, J., Xiao, D., Martinez, O. J., Bartsch, R., Simon, S., Russina, O., Triolo, A., & Quitevis, E. (2011). Effect of Cation Symmetry on the Morphology and Physicochemical Properties of Imidazolium Ionic Liquids. Journal of Physical Chemistry B, 6572 - 6584.