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Issue 46, 2011
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Probing the protic ionic liquid surface using X-ray reflectivity

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Abstract

The structure of the free liquid surface of three protic ionic liquids, ethylammonium nitrate (EAN), propylammonium nitrate (PAN), and ethylammonium formate (EAF), has been elucidated using X-ray reflectivity. The results show all three liquids have an extended interfacial region, spanning at least five ion pairs, which can be divided into two parts. Adjacent to the gas phase are aggregates consisting of multiple cations and anions. Below this are layers oriented parallel to the macroscopic surface that are alternately enriched and depleted in cation alkyl chains and polar domains of cation ammonium groups and their anions, gradually decaying to the isotropic sponge-like bulk structure. The most pronounced layering is observed for PAN, driven by strong solvophobic interactions, while reduced hydrogen bonding in EAF results in the least structured and least extensive interfacial region.

Graphical abstract: Probing the protic ionic liquid surface using X-ray reflectivity

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Publication details

The article was received on 20 Jul 2011, accepted on 27 Sep 2011 and first published on 17 Oct 2011


Article type: Paper
DOI: 10.1039/C1CP22351H
Citation: Phys. Chem. Chem. Phys., 2011,13, 20828-20835
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    Probing the protic ionic liquid surface using X-ray reflectivity

    D. Wakeham, A. Nelson, G. G. Warr and R. Atkin, Phys. Chem. Chem. Phys., 2011, 13, 20828
    DOI: 10.1039/C1CP22351H

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