Protic Ionic Liquids Based on the Alkyl-Imidazolium Cation: Effect of the Alkyl Chain Length on Structure and Dynamics
Artikel i vetenskaplig tidskrift, 2019

Protic ionic liquids are known to form extended hydrogen-bonded networks that can lead to properties different from those encountered in the aprotic analogous liquids, in particular with respect to the structure and transport behavior. In this context, the present paper focuses on a wide series of 1-alkyl-imidazolium bis(trifluoromethylsulfonyl)imide ionic liquids, [HC n Im][TFSI], with the alkyl chain length (n) on the imidazolium cation varying from ethyl (n = 2) to dodecyl (n = 12). A combination of several methods, such as vibrational spectroscopy, wide-angle X-ray scattering (WAXS), broadband dielectric spectroscopy, and 1 H NMR spectroscopy, is used to understand the correlation between local cation-anion coordination, nature of nanosegregation, and transport properties. The results indicate the propensity of the -NH site on the cation to form stronger H-bonds with the anion as the alkyl chain length increases. In addition, the position and width of the scattering peak q 1 (or the pre-peak), resolved by WAXS and due to the nanosegregation of the polar from the nonpolar domains, are clearly dependent on the alkyl chain length. However, we find no evidence from pulsed-field gradient NMR of a proton motion decoupled from molecular diffusion, hypothesized to be facilitated by the longer N-H bonds localized in the segregated ionic domains. Finally, for all protic ionic liquids investigated, the ionic conductivity displays a Vogel-Fulcher-Tammann dependence on inverse temperature, with an activation energy E a that also depends on the alkyl chain length, although not strictly linearly.

Författare

Iqbaal Abdurrokhman

Chalmers, Kemi och kemiteknik, Tillämpad kemi, Anna Martinelli Group

Khalid Elamin

Chalmers, Kemi och kemiteknik, Tillämpad kemi, Anna Martinelli Group

Olesia Danyliv

Chalmers, Kemi och kemiteknik, Tillämpad kemi, Anna Martinelli Group

Mohammad Hasani

Chalmers, Kemi och kemiteknik, Tillämpad kemi, Anna Martinelli Group

Jan Swenson

Chalmers, Fysik, Biologisk fysik

Anna Martinelli

Chalmers, Kemi och kemiteknik, Tillämpad kemi, Anna Martinelli Group

Journal of Physical Chemistry B

1520-6106 (ISSN) 1520-5207 (eISSN)

Vol. 123 18 4044-4054

Ämneskategorier

Fysikalisk kemi

Teoretisk kemi

Den kondenserade materiens fysik

DOI

10.1021/acs.jpcb.9b01274

PubMed

30995045

Mer information

Senast uppdaterat

2019-07-26