We use X-ray scattering to investigate morphology and dielectric spectroscopy to study ionic conduction and dielectric response of imidazolium-based single-ion conductors with two different counterions [hexafluorophosphate (PF 6 -) or bis(trifluoromethanesulfonyl)imide (F 3CSO 2NSO 2CF 3 - = Tf 2N -)] with different imidazolium pendant structures, particularly tail length (n-butyl vs n-dodecyl). A physical model of electrode polarization is used to separate ionic conductivity of the ionomers into number density of conducting ions and their mobility. Tf 2N - counterions display higher ionic conductivity and mobility than PF 6 - counterions, as anticipated by ab initio calculations. Ion mobility is coupled to polymer segmental motion, as these are observed to share the same Vogel temperature. Ionomers with the n-butyl tail impart much larger static dielectric constant than those with the n-dodecyl tail. From the analysis of the static dielectric constant using Onsager theory, there is more ionic aggregation in ionomers with the n-dodecyl tails than in those with the n-butyl tails, consistent with X-ray scattering, which shows a much stronger ionic aggregate peak for the ionomers with dodecyl tails on their imidazolium side chains.
All Science Journal Classification (ASJC) codes
- Organic Chemistry
- Polymers and Plastics
- Inorganic Chemistry
- Materials Chemistry