Imperial College London

Professor Tom Welton

Faculty of Natural SciencesDepartment of Chemistry

Professor of Sustainable Chemistry



+44 (0)20 7594 5763t.welton Website




601AMolecular Sciences Research HubWhite City Campus






BibTex format

author = {Brooks, NJ and Castiglione, F and Doherty, CM and Dolan, A and Hill, AJ and Hunt, PA and Matthews, RP and Mauri, M and Mele, A and Simonutti, R and Villar-Garcia, IJ and Weber, CC and Welton, T},
doi = {10.1039/c7sc01407d},
journal = {Chemical Science},
pages = {6359--6374},
title = {Linking the structures, free volumes, and properties of ionic liquid mixtures},
url = {},
volume = {8},
year = {2017}

RIS format (EndNote, RefMan)

AB - The formation of ionic liquid (IL) mixtures has been proposed as an approach to rationally fine-tune the physicochemical properties of ILs for a variety of applications. However, the effects of forming such mixtures on the resultant properties of the liquids are only beginning to be understood. Towards a more complete understanding of both the thermodynamics of mixing ILs and the effect of mixing these liquids on their structures and physicochemical properties, the spatial arrangement and free volume of IL mixtures containing the common [C4C1im]+ cation and different anions have been systematically explored using small angle X-ray scattering (SAXS), positron annihilation lifetime spectroscopy (PALS) and 129Xe NMR techniques. Anion size has the greatest effect on the spatial arrangement of the ILs and their mixtures in terms of the size of the non-polar domains and inter-ion distances. It was found that differences in coulombic attraction between oppositely charged ions arising from the distribution of charge density amongst the atoms of the anion also significantly influences these inter-ion distances. PALS and 129Xe NMR results pertaining to the free volume of these mixtures were found to strongly correlate with each other despite the vastly different timescales of these techniques. Furthermore, the excess free volumes calculated from each of these measurements were in excellent agreement with the excess volumes of mixing measured for the IL mixtures investigated. The correspondence of these techniques indicates that the static and dynamic free volume of these liquid mixtures are strongly linked. Consequently, fluxional processes such as hydrogen bonding do not significantly contribute to the free volumes of these liquids compared to the spatial arrangement of ions arising from their size, shape and coulombic attraction. Given the relationship between free volume and transport properties such as viscosity and conductivity, these results provide a link between the s
AU - Brooks,NJ
AU - Castiglione,F
AU - Doherty,CM
AU - Dolan,A
AU - Hill,AJ
AU - Hunt,PA
AU - Matthews,RP
AU - Mauri,M
AU - Mele,A
AU - Simonutti,R
AU - Villar-Garcia,IJ
AU - Weber,CC
AU - Welton,T
DO - 10.1039/c7sc01407d
EP - 6374
PY - 2017///
SN - 2041-6520
SP - 6359
TI - Linking the structures, free volumes, and properties of ionic liquid mixtures
T2 - Chemical Science
UR -
UR -
VL - 8
ER -