Conformational Dynamics in an Organic Ionic Plastic Crystal

Liyu Jin*, Kate M. Nairn, Chris D. Ling, Haijin Zhu, Luke A. O'Dell, Jiaye Li, Fangfang Chen, Adriano F. Pavan, Louis A. Madsen, Patrick C. Howlett, Douglas R. Macfarlane, Maria Forsyth, Jennifer M. Pringle

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

38 Scopus citations


Understanding the short-range molecular motions of organic ionic plastic crystals is critical for the application of these materials as solid-state electrolytes in electrochemical devices such as lithium batteries. However, the theory of short-range-motions was originally developed for simple molecular plastic crystals and does not take account of strong interionic interactions that are present in organic ionic plastic crystals. Here we report a fundamental investigation of the dynamic behavior of an archetypal example triethyl(methyl)phosphonium bis(fluorosulfonyl)amide ([P1222][FSI]) through calorimetry, impedance spectroscopy, synchrotron X-ray diffraction, and solid-state NMR and Raman spectroscopies. For the first time, we show the presence of conformational dynamics in the solid state for the FSI anion. We relate the dynamics to a unique second-order displacive phase transition of [P1222][FSI]. This detailed analysis suggests a new disorder mechanism involving cooperative motion between the cation and FSI anion in the plastic crystal due to strong interionic interactions.

Original languageEnglish
Pages (from-to)5439-5446
Number of pages8
JournalJournal of Physical Chemistry B
Issue number21
StatePublished - 1 Jun 2017
Externally publishedYes


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