Molecular dynamics simulations of temperature-dependent structures and dynamics of ethylammonium nitrate protic ionic liquid: The role of hydrogen bond

- Hydrogen bonds play an essential role in determining dynamics properties of protic ionic liquids.
- Temperature has an important influence on dynamics properties rather than structures.
- Both anions and cations are found to display an obvious sub-diffusive behavior regardless of the temperature.

Molecular dynamics simulations have been employed to systematically investigate the structure and dynamics properties, hydrogen bond (HB) dynamics of protic ionic liquid (IL) ethylammonium nitrate (EAN) in the temperature range between 300 K and 400 K. The simulation results demonstrate clearly that the temperature almost has little influence on the structures of EAN IL, whereas the translational and the rotational motions of both cations and anions become much faster at higher temperatures. Furthermore, both anions and cations are found to display an obvious sub-diffusive behavior. These changes can be attributed to the temperature-dependent HB strength between the cations and the anions, where the strength of HBs decreases significantly with increasing temperature. Accordingly, the ion-pair association/dissociation dynamics decreases considerably with increasing temperature. Therefore, our simulations reveal at a molecular level that the HBs interactions play an essential role in determining the dynamics properties of protic ILs.

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