Viscosity relationship with ionic conductivity

Walden s rule in electrochemistry describes the relationship between ionic conductivity o with viscosity r, that is, o x r = constant. 3 The electrochemical molar conductivity (Amp) can be calculated from ionic conductivity as Amp = oM/p, where M is the molecular weight and p is the density. The Walden plots of the molecular conductivity versus 1/in the unit of 0.1 Pas (=poise) proposed by Angell and coworkers24 are shown in Fig. 15 for the present four ILs. The Walden rule relates the molecular mobility (1/ tf) to the molar conductivity induced from the charged ions in solution electrolytes and characterizes ILs. The fully dissociated ions such as diluted aqueous KCl solution give a behavior shown as a line in Fig. 15. The deviation from the ideal plot, ZllVhas been proposed to relate with the ion pairing of ILs.25 In the present ILs, the ZlIV for EMIm-TFSA exhibited the smallest value, followed by DMPIm-TFSA, DEME-TFSA and Pis-TFSA. 

Ionic liquid conductivity appears to be most strongly correlated with viscosity (q). Figure 3.6-3 shows a plot of conductivity versus viscosity for the data in Tables 3.6-3-3.6-5. This figure clearly demonstrates an inverse relationship between conductivity and viscosity. 

Prediction models for ionic conductivity and viscosity of ILs using quantitative structure property relationships coupled with the descriptors of group contribution type were introduced [155], The polynomial expansion model based on the type of cation, length of side chain, and type of anion was applied to the expression of IL properties. Parameters of these polynomial expansion models were determined by means of a genetic algorithm. The reverse design of ILs was also tested [155],... 

Equation [3.7] correlates conductivity with ionic diffusion and electrolyte viscosity. Since the Nernst-Einstein equation [3.8] gives the relationship between conductivity and diffusion and since the right-hand side of equation [3.7] is obtained by combining equations [3.6] and [3.8], the decoupling index R, is basically a measure of the effect of viscosity on conductivity. 

The ionic conductivity against the inverse viscosity based on Walden rule [34] is shown in Fig. 6.12. The relationship between these physicochemical properties under the same condition in log-log scale displayed clearly a straight line. This result also indicated that a kind of Walden rule (trri = constant) was applicable for [P2225KTFSA] including [Nd(TFSA)s] with and without trace amotmts of water. 

In this equation, a is the conductivity, A is a constant proportional to the number of carrier ions, B is a constant, and To is the temperature at which the configurational entropy of the polymer becomes zero and is close to the glass transition temperature (Tg). The VTF equation fits conductivity rather well over a broad temperature range extending from Tg to about Tg +100 K. Equation [3.2] is an adaptation of the William-Landel-Ferry WLF relationship developed to explain the temperature dependence of such polymer properties as viscosity, dielectric relaxation time and magnetic relaxation rate. The fact that this equation can be applied to conductivity implies that, as with these other properties, ionic... 

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