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摘要
Amino acid ionic liquids [C(n)mim] [Ala] (n = 3, 4, 5) (1-alkyl-3-methylimidazolium alanine salt) were prepared by the neutralization method. The density and viscosity for aqueous solutions of the ionic liquids (ILs) with various molalities were measured at T = (288.15 to 328.15), K with an interval of 5 K. In terms of the Jones Dole equation, the viscosity B-coefficients with large positive values and dB/dT < 0 were obtained, and these facts implied that the ionic liquids are water-structure-making. According to Feakins, the contribution of the solute per mole to the free energy of activation for viscous flow of the solution, Delta mu(double dagger 0)(2), or called as the standard molar activation free energy, was obtained at different temperatures. Under the constant molality of solution, Delta H-2(double dagger 0) (the activation enthalpy of the activation for viscous flow of aqueous [C(n)mim][Ala] (n = 3, 4, 5)) is a temperature-independent constant. This implies that the activation process of the solute for viscous flow of aqueous [C(n)mim] [Ala] (n = 3, 4, 5) is an isoCoulombic reaction. A semiempirical method to estimate the viscosity of aqueous [C(n)mim] [Ala] (n = 3, 4, 5) was put forward based on Eyring's theory, and the estimated viscosity values of the aqueous ILs are in good agreement with the corresponding experimental ones.
