Polymerized ionic liquids (PILs) are promising candidates for solid polymer electrolytes applications. They present an opportunity to combine the intrinsic high ionic conductivity of ionic liquids and superior mechanical property of polymers, while keeping the transference number of the untethered ions close to unity. A systematic study has been carried out to provide a better understanding of the ion transport mechanism in PILs. By using broadband dielectric spectroscopy, together with differential scanning calorimetry, our analysis reveals a decoupling of conductivity relaxation from the segmental relaxation in all the PIL samples. This observation stands in stark contrast to the behavior of aprotic ILs, where the ion transport and structural dynamics are closely coupled. Rheological study shows that both samples A and F have extensive aggregates of long lifetime and samples B, C, D and E have identical mechanical spectra. We find that the global chain dynamics and large scale aggregation have little effect on the decoupling phenomena and the ion transport is determined mainly by the local dynamics in our samples. Our study demonstrates that understanding and promoting the decoupling of conductivity from segmental relaxation is the key for designing highly conductive polymerized ionic liquids in electrochemical applications.

Decoupling of conductivity from segmental relaxation in polymerized ionic liquids

248th National Meeting (2014)

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