Densities, viscosities, and transport properties

Densities are higher for fhe alkoxymethyl(2-hydroxyefhyl)-dimefhylam-monium salfs fhan for (2-acefoxyefhyl)alkoxymefhyl-dimefhylammonium salts [21]. The increases of fhe alkyl chain at the cation from efhyl- to dodecyl-decrease the density from 1.45 to 1.21 g cm . The densities of imidazolium salfs with popular cation [CjCilm] are presented in Table 1.1. 

It is easy to notice that the lowest value of densify is with dicyanamide anion, [dca] , and the highest with the l7/s(trifluoromethylsultonyl)imide anion, [Tf2N]-. 

Transport properties play an important role in chemical reactions, electrochemistry, and liquid-liquid extraction. This concerns mainly the viscosity of ILs and fheir solutions wifh molecular solvenfs. Viscosity of ILs, typically at the level of 10-500 cP af room femperafure, is much higher than that characteristic of wafer ( /(HjO) = 0.89 cP af 298.15 K) and aqueous solutions. The high dynamic viscosity (viscosity coefficient) of ILs causes difficulties 

Viscosity temperature dependence in ILs is more complicated than in most molecular solvents, because most of them do not follow the typical Arrhenius behavior. Most temperature studies fit the viscosity values into the Vogel-Tammarm-Fulcher (VTF) equation, which adds an additional adjustable parameter (glass transition temperature) to the exponential term. 

In general, all ILs show a significant decrease in viscosity as the temperature increases. A systematic study of a possible description covering ILs by the Arrhenius or VTF equations was made by Okoturo and Van der Noot [44]. 

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