Study on the properties of density, viscosity, excess molar volume, and viscosity deviation of [C2mim][NTf2], [C2mmim][NTf2], [C4mim][NTf2], and [C4mmim][NTf2] with PC binary mixtures

The imidazolium type ionic liquids (ILs) 1-alkyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl] imide ([C2mim][NTf2] and [C4mim][NTf2]) were synthesized. For comparing, the ILs with introduction of methyl group 1-alkyl-2,3-dimethylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([C2mmim][NTf2] and [C4mmim][NTf2]) were also prepared. The density and viscosity of the systems composed of above ILs and propylene carbonate (PC) were determined. The determined uncertainties are u(ρ) = 0.00010 g·cm−3 for density and ur(η) = 0.02 for viscosity, respectively. The excess molar volumes, thermal expansion coefficients, viscosity deviations, and a-constant were calculated. According to Redlich−Kister equation, the relationship between excess molar volume, viscosity deviation and mole fraction was fitted. By comparing with the systems of the same ILs in other organic solvents, the above-mentioned properties were discussed and the influence of introduced methylene group and methyl group on the above properties was analyzed. •The four systems of ILs [C2mim][NTf2], [C2mmim][NTf2], [C4mim][NTf2], [C4mmim][NTf2] with PC were prepared.•The density, viscosity, excess molar volume, and viscosity deviation of the systems have been measured and discussed.•Influences of –CH3 and –CH2– groups on properties were discussed.•The thermal expansion coefficient, α/K−1, has also been calculated in the studied concentration range.•The constant, a, has also been calculated in the studied temperature range.