Introducing Large Counteranions Enhances the Elastic
Modulus of Imidazolium-Based Polymerized Ionic Liquids
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Abstract
Polymerized ionic liquids (PILs)
are believed to be ideal solid-state
polymer electrolytes, and hence experimental and computational studies
have been widely undertaken to understand the relationship between
the chemical structure and mechanical/dielectric properties and the
ionic conductivity of PILs. However, it is still a challenge to understand
the effect of counterion ionic volume on the material properties of
PILs. Herein, we demonstrate the effect of the ionic volume ratio
of counteranions to side-chain cations on linear viscoelastic response
using three imidazolium-based PILs with different counteranions. We
show that the elastic modulus is significantly enhanced at temperatures
higher than glass transition temperature once the ionic volume of
the counteranion exceeds that of the side-chain cation. Our results
provide an additional strategy to improve mechanical properties of
PILs, while maintaining relatively high ionic conductivity