Surface tensions of ionic liquids: Non-regular trend along the number of cyano groups
authors Almeida, HFD; Carvalho, PJ; Kurnia, KA; Lopes-da-Silva, JA; Coutinho, JAP; Freire, MG
nationality International
journal FLUID PHASE EQUILIBRIA
author keywords Surface tension; Ionic liquids; Imidazolium-based; Cyano-based Surface entropy; Surface enthalpy; Critical temperature; COSMO-RS
keywords THERMOPHYSICAL PROPERTIES; REFRACTIVE-INDEX; CARBON-DIOXIDE; CHAIN-LENGTH; TEMPERATURE; ANIONS; ENERGY; WATER; VISCOSITY; 1-HEXYL-3-METHYLIMIDAZOLIUM
abstract Ionic liquids (ILs) with cyano-functionalized anions are a set of fluids that are still poorly characterized despite their remarkably low viscosities and potential applications. Aiming at providing a comprehensive study on the influence of the number of -CN groups through the surface tension and surface organization of ILs, the surface tensions of imidazolium-based ILs with cyano-functionalized anions were determined at atmospheric pressure and in the (298.15-343.15) K temperature range. The ILs investigated are based on 1-alkyl-3-methylimidazolium cations (alkyl = ethyl, butyl and hexyl) combined with the [SCN](-), [N(CN)(2)](-), [C(CN)(3)](-) and [B(CN)(4)](-) anions. Although the well-known trend regarding the surface tension decrease with the increase of the size of the aliphatic moiety at the cation was observed, the order obtained for the anions is more intricate. For a common cation and at a given temperature, the surface tension decreases according to: [N(CN)(2)](-) > [SCN](-) > [C(CN)(3)](-) > [B(CN)(4)](-). Therefore, the surface tension of this homologous series does not decrease with the increase of the number of -CN groups at the anion as has been previously shown by studies performed with a more limited matrix of ILs. A maximum in the surface tension and critical temperature was observed for [N(CN)2]-based ILs. Furthermore, a minimum in the surface entropy, indicative of a highly structured surface, was found for the same class of ILs. All these evidences seem to be a result of stronger hydrogen-bonding interactions occurring in [N(CN)(2)]-based ILs, when compared with the remaining CN-based counterparts, and as sustained by cation-anion interaction energies derived from the Conductor Like Screening Model for Real Solvents (COSMO-RS). (C) 2015 Elsevier B.V. All rights reserved.
publisher ELSEVIER SCIENCE BV
issn 0378-3812
year published 2016
volume 409
beginning page 458
ending page 465
digital object identifier (doi) 10.1016/j.fluid.2015.10.044
web of science category Thermodynamics; Chemistry, Physical; Engineering, Chemical
subject category Thermodynamics; Chemistry; Engineering
unique article identifier WOS:000367860400050
  ciceco authors
  impact metrics
journal analysis (jcr 2017):
journal impact factor 2.197
5 year journal impact factor 2.214
category normalized journal impact factor percentile 57.695
dimensions (citation analysis):
altmetrics (social interaction):



 


Apoio

1suponsers_list_ciceco.jpg