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Influence of Counterion Structure on Conductivity of Polymerized Ionic Liquids
journal contribution
posted on 2019-03-25, 15:57 authored by Jordan
R. Keith, Nathan J. Rebello, Benjamin J. Cowen, Venkat GanesanWe
performed long-time all-atom molecular dynamics simulations
of cationic polymerized ionic liquids with eight mobile counterions,
systematically varying size and shape to probe their influence on
the decoupling of conductivity from polymer segmental dynamics. We
demonstrated rigorous identification of the dilatometric glass-transition
temperature (Tg) for polymerized ionic
liquids using an all-atom force field. Polymer segmental relaxation
rates are presumed to be consistent for different materials at the
same glass-transition-normalized temperature (Tg/T), allowing us to extract a relative order
of decoupling by examining conductivity at the same Tg/T. Size, or ionic volume, cannot fully
explain decoupling trends, but within certain geometric and chemical-specific
classes, small ions generally show a higher degree of decoupling.
This size effect is not universal and appears to be overcome when
structural results reveal substantial coordination delocalization.
We also reveal a universal inverse correlation between ion-association
structural relaxation time and absolute conductivity for these polymerized
ionic liquids, supporting the ion-hopping interpretation of ion mobility
in polymerized ionic liquids.
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ion mobilityion-hopping interpretationrelaxation timeconductivityrelaxation ratesglass-transition-normalized temperaturesize effectall-atom force fieldcationic polymerizedcoordination delocalizationchemical-specific classesCounterion Structuredilatometric glass-transition temperatureT gdynamics simulationsdecoupling trends
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