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

Journal Article · Thu Oct 15 04:00:00 EDT 2015 · Faraday Discussions

DOI:https://doi.org/10.1039/C1FD00059D· OSTI ID:1034951

Kashyap, Hemant K.; Santos, Cherry S.; Annapureddy, Harsha V.R.; Murthy, N. Sanjeeva; Margulis, Claudio J.

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 {angstrom}{sup -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 {angstrom}{sup -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 {angstrom}{sup -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.

• Research Organization: Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
• Sponsoring Organization: DOE - BASIC ENERGY SCIENCES
• OSTI ID: 1034951
• Journal Information: Faraday Discussions, Journal Name: Faraday Discussions Journal Issue: 2012 Vol. 154; ISSN 1359-6640
• Country of Publication: United States
• Language: ENGLISH