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Elucidating the Correlation between Morphology and Ion Dynamics in Polymerized Ionic Liquids

Wednesday, 4 October 2017
Prince George's Exhibit Hall D/E (Gaylord National Resort and Convention Center)
M. F. Heres, J. T. Cosby (University of Tennessee Knoxville), V. Strehmel (Hochschule Niederrhein University of Applied Sciences), R. Benson (University of Tennessee Knoxville), and J. R. Sangoro (University of Tennessee, Knoxville)
The impact of chemical structure on ion dynamics and morphology in ammonium and imidazolium based polymerized ionic liquids (polyIL) are investigated using broadband dielectric spectroscopy and wide angle X-ray scattering (WAXS). Increasing the alkyl chain length results in longer backbone-to-backbone spacing of the adjacent polymer chains. In the ammonium-based systems this increase correlates with the Tg-independent ionic conductivity and activation energies associated with ion hopping below Tg. In contrast, imidazolium systems show weak dependence of ion dynamics on alkyl chain lengths. In addition, we find that the Tg-independent ionic conductivity of the acrylate-derived ammonium systems and the vinyl-derived imidazolium polymers does not depend upon the placement of the ion within the polymer structure, but rather the chemical structure of the cation, volume of the counterion and the morphology. The implications of these results on the design of novel polymerized ionic liquids for electrochemical energy applications will be discussed.