Effect of cation symmetry on probe rotational diffusion in ionic liquids studied by fluorescence recovery after photobleaching
Udugama-A., Rakhitha W. Sumanasekara
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The glass transition (Tg) is an interesting but challenging problem. Although this phenomenon has been studied for over half a century, Tg is still not well understood especially at the molecular level. One important feature which seems to be missing in the current understanding is its inherent heterogeneous dynamics. Ionic liquids are used in this study because of their fascinating physicochemical properties and they have been extensively studied in last two decades. The ability to change their structure to obtain a desired property for a specific application and the possibility of making millions of ionic liquids are very important characteristics in ILs. Understanding of the structure and dynamics of ILs and their mixtures with common solvents is necessary for their use in variety of applications and in their improvements. The dynamics of imidazolium-based ionic liquids were investigated near Tg. Ionic liquids are unique in terms of their structure and dynamics. Imidazolium-based ionic liquids are known for their structural hetereogeneity through the formation polar and nonpolar domains in the liquid state and their dynamical heterogeneity in the liquid and glassy state. Symmetric effect of cations in imidazolium-based ionic liquids was investigated. These studies showed that the dynamic heterogeneity cannot be necessarily explained by the structural heterogeneity near Tg.