title: Densities, Viscosities and Derived Thermophysical Properties of Water-Saturated Imidazolium-Based Ionic Liquids.
abstract: In order to evaluate the impact of the alkyl side chain length and symmetry of the cation on the thermophysical properties of water-saturated ionic liquids (ILs), densities and viscosities as a function of temperature were measured at atmospheric pressure and in the (298.15 to 363.15) K temperature range, for systems containing two series of bis(trifluoromethylsulfonyl)imide-based compounds: the symmetric [CnCnim][NTf2] (withn= 1-8 and 10) and asymmetric [CnC1im][NTf2] (withn= 2-5, 7, 9 and 11) ILs. For water-saturated ILs, the density decreases with the increase of the alkyl side chain length while the viscosity increases with the size of the aliphatic tails. The saturation water solubility in each IL was further estimated with a reasonable agreement based on the densities of water-saturated ILs, further confirming that for the ILs investigated the volumetric mixing properties of ILs and water follow a near ideal behaviour. The water-saturated symmetric ILs generally present lower densities and viscosities than their asymmetric counterparts. From the experimental data, the isobaric thermal expansion coefficient and energy barrier were also estimated. A close correlation between the difference in the energy barrier values between the water-saturated and pure ILs and the water content in each IL was found, supporting that the decrease in the viscosity of ILs in presence of water is directly related with the decrease of the energy barrier.
authors.affiliation: CICECO - Aveiro Institute of Materials, Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: Mónia A R
authors.initials: MA
authors.lastname: Martins
authors.affiliation: CICECO - Aveiro Institute of Materials, Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: Catarina M S S
authors.initials: CM
authors.lastname: Neves
authors.affiliation: CICECO - Aveiro Institute of Materials, Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: Kiki A
authors.initials: KA
authors.lastname: Kurnia
authors.affiliation: CICECO - Aveiro Institute of Materials, Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: Pedro J
authors.initials: PJ
authors.lastname: Carvalho
authors.affiliation: Centro de Investigação em Química, Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade do Porto, R. Campo Alegre 687, 4169-007 Porto, Portugal; Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, Den Dolech 2, 5612 AZ Eindhoven, The Netherlands.
authors.forename: Marisa A A
authors.initials: MA
authors.lastname: Rocha
authors.affiliation: Centro de Investigação em Química, Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade do Porto, R. Campo Alegre 687, 4169-007 Porto, Portugal.
authors.forename: Luís M N B F
authors.initials: LM
authors.lastname: Santos
authors.affiliation: Associate Laboratory LSRE/LCM, Departamento de Tecnologia Química e Biológica, Instituto Politécnico de Bragança, Campus de Santa Apolónia, 5301-857 Bragança, Portugal; UNIFACS-Universidade de Salvador, Rua Dr. José Peroba 251, CEP 41770-235, Salvador, Brazil.
authors.forename: Simão P
authors.initials: SP
authors.lastname: Pinho
authors.affiliation: CICECO - Aveiro Institute of Materials, Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: Mara G
authors.initials: MG
authors.lastname: Freire
keywords: Bis(trifluoromethylsulfonyl)imide; Density; Imidazolium; Ionic Liquids; Viscosity; Water