abstract
Densities, viscosities and refractive index, as a function of temperature, and isobaric thermal expansion coefficient, were determined for 1-alkyl-3-methylimidazolium hexafluorophosphate, [C(N - 1)C(1)im]PF6] (where N = 5 to 10) series of ionic liquids. The density presents a regular decrease along the ionic liquid series, with no detectable alkyl chain length dependence of the thermal expansion coefficient. Both the refractive index and viscosity show a trend shift along the series around the [C(6)C(1)im][PF6] that could be associated to the impact of the change in the nanostructuration of the ionic liquids. The experimental results are compared with the analogous [C(N - 1)C(1)im][NTf2] series and the effect of the anion is analyzed. The sphericity of the [PF6](-) anion is reflected in the lower pre-exponential VTF parameter, A(eta), and the higher viscosity of the [C(N - 1)C(1)im][PF6]. when compared with the [C(N - 1)C(1)im][NTf2] series, is ruled by the higher energy barriers, which are related with stronger electrostatic interaction due to the low charge dispersion of the [PF6](-),anion. (C) 2013 Elsevier B.V. All rights reserved.
keywords
HIGH-PRESSURE DENSITIES; IUPAC TECHNICAL REPORT; THERMODYNAMIC PROPERTIES; 1-BUTYL-3-METHYLIMIDAZOLIUM HEXAFLUOROPHOSPHATE; HEAT-CAPACITIES; 1-HEXYL-3-METHYLIMIDAZOLIUM HEXAFLUOROPHOSPHATE; TEMPERATURE-DEPENDENCE; PHYSICAL-PROPERTIES; ORGANIC-SOLVENTS; SMALL SAMPLES
subject category
Chemistry; Physics
authors
Rocha, MAA; Ribeiro, FMS; Ferreira, AIMCL; Coutinho, JAP; Santos, LMNBF
our authors
acknowledgements
This work was supported by FCT, Lisbon, Portugal, and the European Social Fund through strategic projects Pest-C/QUI/U10081/2011 awarded to CIQUP and Pest-C/CTM/LA0011/2011 to CICECO. M.A.A. Rocha and A.I.M.C.L. Ferreira acknowledge the financial support from FCT for the award of research grants with references, SFRH/BD/60513/2009 and SFRH/BPD/84891/2012 respectively.