abstract
Experimental data on the surface tension and refractive index of tetradecyltrihexylphosphonium-based ionic liquids with bromide, chloride, decanoate, methanesulfonate, dicyanimide, bis(2,4,4-trimethylpentyl)phosphinate and bis(trifluoromethylsulfonyl)imide anions are reported. The data were obtained for pure and water saturated samples at temperatures from 283 K to 353 K and at atmospheric pressure. The refractive index of the investigated ionic liquids decreases with increasing the water content in the sample. On the other hand, no clearly dependence of the surface tension with the water content up to a weight fraction of 16% was found. The prediction of the refractive index for the studied ionic liquids was also accomplished by a group contribution method and new values for the cation and diverse anions were estimated and proposed. The studied ionic liquids show lower surface tension in comparison with imidazolium-, pyridinium-or pyrrolidinium-based ionic liquids with a similar anion; also they show higher surface entropy than cyclic nitrogen-based fluids which indicates a lower surface organization. The anion dependence of the surface tension and surface entropy for the investigated ionic liquids is weaker than that for short-chain imidazolium-based ionic liquids. Their critical temperatures evaluated from Eotvos and Guggenheim equations are also lower than those of N-heterocyclic ionic fluids. (C) 2012 Elsevier Ltd. All rights reserved.
keywords
HIGH-PRESSURE DENSITIES; ALKYL CHAIN-LENGTH; PHYSICAL-PROPERTIES; THERMOPHYSICAL PROPERTIES; THERMODYNAMIC PROPERTIES; TEMPERATURE; IMIDAZOLIUM; ANION; MIXTURES; CATION
subject category
Thermodynamics; Chemistry
authors
Almeida, HFD; Lopes-da-Silva, JA; Freire, MG; Coutinho, JAP
our authors
Mara Guadalupe Freire Martins
Coordinating ResearcherGroups
G4 - Renewable Materials and Circular Economy
G5 - Biomimetic, Biological and Living Materials
acknowledgements
The authors acknowledge the financial support from Fundacao para a Ciencia e a Tecnologia (FCT) for the projects PTDC/EQU-FTT/102166/2008 and Pest-C/CTM/LA0011/2011. M. G. Freire acknowledges FCT for the post-doctoral Grant SFRH/BPD/41781/2007. The authors also acknowledge Cytec Industries Inc. for the ionic liquids samples.