Abstract

Self-diffusion and NMR relaxation of the ethylammonium (EA) cation were studied in the protic ionic liquid, ethylammonium nitrate (EAN), confined between polar glass plates separated by a few μm distance and exposed to an external magnetic field of 9.4 T. The diffusion coefficient of EA (D) and the transverse NMR relaxation rate (1/T2) of -NH3 protons were increased immediately after placing the sample in the magnetic field by factors of ∼2 and ∼22, respectively, in comparison with those of bulk EAN. Further exposure of the sample to the magnetic field led to gradual changes in D, T1 and T2 towards their bulk values with a time constant of ∼70 min. Complete "recovery" of the sample to the "accelerated" D and "shortened" T2 values occurred at longer than 24 hours after the removal of the EAN sample from the magnet. Because the observed characteristic times of the change far exceed the times of molecular processes in EAN, we suggested that this phenomenon is related to reversible phase transformations occurring in confined EAN.

Highlights

  • Ionic liquids (ILs) are molten salts prepared from organic cations and either organic or inorganic anions.[1,2] Their applications are continuously expanding, including their use, for instance, as electrolyte materials in lithium batteries[3] and ultracapacitors,[4] as media for chemical reactions and separation,[2,5] and as lubricants.[6]

  • The silanization protocol is described in the Electronic supplementary information (ESI).† In this case, D in the Ethylammonium nitrate (EAN) layers between glass plates was close to D0 and no alteration occurred after placement of the sample in the magnetic field

  • We suggested that the processes occurring with EAN between polar glass plates are the reversible phase transformations of EAN

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Summary

Introduction

Ionic liquids (ILs) are molten salts prepared from organic cations and either organic or inorganic anions.[1,2] Their applications are continuously expanding, including their use, for instance, as electrolyte materials in lithium batteries[3] and ultracapacitors,[4] as media for chemical reactions and separation,[2,5] and as lubricants.[6]. We report the effect of applying a strong magnetic field to EAN confined between polar glass plates separated by B4 mm. 70 min) decrease in the diffusion coefficient of the EA cation and a gradual increase in T2 NMR relaxation times for EA –NH3 protons toward the bulk values of EAN.

Results
Conclusion
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