abstract
In this work, we demonstrate that the presence of fluorinated alkyl chains in Ionic Liquids (ILs) is highly relevant in terms of their thermophysical properties and aqueous phase behaviour. We have measured and compared the density and viscosity of pure 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate, [C(2)C(1)im][FAP], with that of pure 1-ethyl-3-methylimidazolium hexafluorophosphate, [C(2)C(1)im][PF6], at atmospheric pressure and in the (288.15 to 363.15) K temperature range. The results show that the density of [C(2)C(1)im][PF6] is lower than that of [C(2)C(1)im][PF6], while the viscosity data reveal the opposite trend. The fluid phase behaviour of aqueous solutions of the two ILs was also evaluated under the same conditions and it was found that the mutual solubilities of [C(2)C(1)im][FAP] and water are substantially tower than those verified with [C(2)C(1)im][PF6]. The experimental data were lastly interpreted at a molecular level using Molecular Dynamics (MD) simulation results revealing that the interactions between the IL ions and the water molecules are mainly achieved via the six fluorine atoms of [PF6] and the three analogues in [FAP]. The loss of three interaction centres when replacing [PF6] by [FAN, coupled with the bulkiness and relative inertness of the three perfluoroethyl groups, reduces its mutual solubility with water and also contributes to a lower viscosity displayed by the pure [FAP]-based IL as compared to that of the [PF6]-based compound.
keywords
MOLECULAR-FORCE FIELD; TEMPERATURE-DEPENDENCE; MUTUAL SOLUBILITIES; SURFACE-TENSION; BINDING-ENERGY; PLUS LIQUID; WATER; ANIONS; TRIS(PENTAFLUOROETHYL)TRIFLUOROPHOSPHATE; EQUILIBRIA
subject category
Chemistry; Physics
authors
Neves, CMSS; Kurnia, KA; Shimizu, K; Marrucho, IM; Rebelo, LPN; Coutinho, JAP; Freire, MG; Lopes, JNC
our authors
Catarina Maia Seco Seiça Neves
Assistant Researcher
Kiki Adi Kurnia
Post-doc Fellowship
Mara Guadalupe Freire Martins
Coordinating ResearcherGroups
G4 - Renewable Materials and Circular Economy
G5 - Biomimetic, Biological and Living Materials
Projects
Igy Technology: A Purication Platform using Ionic-Liquid-Based Aqueous Biphasic Systems (IGYPURTECH)
acknowledgements
This work was financed by national funding from FCT-Fundacao para a Ciencia e a Tecnologia, through the projects PTDC/AAC-AMB/119172/2010, FCT-ANR/CTM-NAN/0135/2012 (including a post-doctoral grant of K. Shimizu), PTDC/CTM-NAN/121274/2010, PEst-OE/QUI/UI0100/2013 and PEst-C/CTM/LA0011/2013. C.M.S.S. Neves and K.A. Kurnia also acknowledge FCT for their doctoral (SFRH/BD/70641/2010) and post-doctoral (SFRH/BPD/41781/2007) grants. M. G. Freire acknowledges the European Research Council (ERC) for the Starting Grant ERC-2013-StG-337753.