Understanding the kinetics of ionic transport in concentrated electrolytes such as ionic liquids and charged polymers is a topic of great fundamental interest and technological relevance. In this talk, I'll present our theoretical and experimental efforts in understanding the kinetics of ionic transport in ionic liquids and polymerized ionic liquids. In particular, Lord Rayleigh's dissipation function formalism (called the Rayleighian approach) is used for analyzing impedance of ionic liquids (ILs) and polymerized ionic liquids (PILs) within linear response. The approach provides a computational framework for a systematic study of various factors, including polymer dynamics in affecting the impedance. We have used the approach to extract mutual diffusion constants, the length scale of mutual diffusion, and thicknesses of a low dielectric layer on the electrodes from the broadband dielectric spectroscopy (BDS) measurements done for an IL and three PILs. Also, static dielectric permittivities of the IL and the PILs are determined. The extracted mutual diffusion constants are compared with the diffusion constants of ions measured using pulse-field gradient (PFG) fluorine nuclear magnetic resonance (NMR). For the first time, excellent agreements between the diffusivities extracted from the BDS spectra of IL/PILs and those measured using the PFG-NMR are found. The agreement allows the use of the BDS and the PFG-NMR techniques in a complimentary manner for understanding the ionic transport. Reasons behind failure of the models based on the linearized Poisson-Nernst-Planck (PNP) formalism in analyzing the concentrated ionic fluids will be discussed.

Rayleighian approach for studying the kinetics of ionic transport in polymeric media

253rd National Meeting (2017)

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