Volume 154, 2012

Temperature-dependent structure of ionic liquids: X-ray scattering and simulations

Abstract

In this article we determine the temperature-dependent structure of the tetradecyltrihexylphosphonium bis(trifluoromethylsulfonyl)amide ionic liquid using a combination of X-ray scattering and molecular dynamics simulations. As in many other room-temperature ionic liquids three characteristic intermolecular peaks can be detected in the structure function S(q). A prepeak or first sharp diffraction peak is observed at about q = 0.42 Å−1. Long range anion-anion correlations are the most important contributors to this peak. In all systems we have studied to date, this prepeak is a signature of solvation asymmetry. The peak in S(q) near q = 0.75 Å−1 is the signature of ionic alternation and arises from the charge ordered separation of ions of the same charge. The most intense diffraction peak near q = 1.37 Å−1 arises from short-range separation between ions of opposite charge combined with a significant contribution from cationic carbon-carbon interactions, indicating that cationic hydrophobic tails have significant contacts.

Article information

Article type
Paper
Submitted
05 Apr 2011
Accepted
15 Jun 2011
First published
19 Jul 2011

Faraday Discuss., 2012,154, 133-143

Temperature-dependent structure of ionic liquids: X-ray scattering and simulations

H. K. Kashyap, C. S. Santos, H. V. R. Annapureddy, N. S. Murthy, C. J. Margulis and E. W. Castner, Jr, Faraday Discuss., 2012, 154, 133 DOI: 10.1039/C1FD00059D

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