Water volume-conductivity fraction

The above differences observed with the various cosurfactants are reflected in the conductivity - water volume fraction This is shown in Figures 5 and 6. It can be... 

InrxLiences of alcohol isomery on the conductivity - water volume fraction curve (symbols are the same as those for Figure 4). 

Thus, in summary, self diffusion measurements by Lindman et a (29-34) have clearly indicated that the structure of microemulsions depends to a large extent on the chain length of the oosurfactant (alcohol), the surfactant and the type of system. With short chain alcohols (hydrophilic domains and the structure is best described by a bicontinuous solution with easily deformable and flexible interfaces. This picture is consistent with the percolative behaviour observed when the conductivity is measured as a function of water volume fraction (see above). With long chain alcohols (> Cg) on the other hand, well defined "cores" may be distinguished with a more pronounced separation into hydrophobic and hydrophilic regions. 

The highest level, at structural scales >10 nm, is that over which long-range transport takes place and diffusion depends on the degree of connectivity of the water pockets, which involves the concept of percolation. The observed decrease in water permeation with decreasing water volume fraction is more pronounced in sulfonated poly(ether ketone) than in Nafion, owing to differences in the state of percolation. Proton conductivity decreases in the same order, as well. 

Figure 12. Water self-diffusion coefficient of Nafion 117 (EW =1100 g/equiv), as a function of the water volume fraction Xy and the water diffusion coefficient obtained from a Monte Carlo (MC) simulation (see text). The proton conductivity diffusion coefficient (mobility) is given for comparison. The corresponding data points are displayed in Figure 14.

EFFECT OF WATER VOLUME FRACTION ON ELECTRICAL CONDUCTIVITY AND ION DIFFUSIVITY IN AGAROSE GELS... 

The electrical conductivity of agarose gel increased with increasing water volume fraction, Figure 1. This is attributed primarily to the dependence of ion diffusivity on water volume fraction [14], An empirical model for relative ion diffusivity (D/Do) is proposed to be a function of the hydrodynamic radius ( rs) of solute and intrinsic Darcy permeability (k) of gel ... 

Effect of Water Volume Fraction on Electrical Conductivity and Ion... 

Electrical conductivity versus volume fraction for three series of water in oil microemulsions versus salinity. Circles correspond to the microemulsions obtained from phase separation. 

Figure 15.11 Variation of conductivity with water volume fraction for various cosurfactants.

Figure 23.5 Proton conductivity and water diffusion coefficient (D and Dh2o) of hydrated Nafion as a function of its water volume fraction. Data are taken from Refs. [12, 43, 77, 78, 108-116], unpublished data from the author s...

Figure 15 indicates the variations of the emulsion electrolytic conductivity vs. formulation (aqueous phase salinity) at different constant water-to-oil ratios, indicated by the water volume fraction/. (83). When/ ranges from 0.4 to 0.7, the conductivity exhibits the typical pattem, already mentioned in the previou.s section. Suboptimum salinity (SAD < 0) is associated to O/W emulsions, while overoptimum salinity results in W/0 ones. There is, however, a slight change in... 

Figure 12.1. The dependence of proton mobility on water content, (a) Proton selfdiffusion coefficients (D

Fig, 11. Comparative conductive behavior of water-in-hexadecane systems using potassium oleate as the surfactant and either 1-pentanol or 1-hexanol. Soap to alcohol mass ratio equal to 3/5. Combined soap and alcohol mass fraction p equal to 0.40. represents the water volume fraction. Temperature T = 25°C. 

The system based on butanol shows a rapid increase in k above a critical water volume fraction value, whereas the second system based on hexanol shows much lower conductivity, with a maximum and minimum at two water volume fractions,... 

Fig. 10.14. Conductivity versus water volume fraction for two W/O microemulsion systems.

With the short-chain alcohols (C < 5), the conductivity shows a rapid increase above a critical rj). With longer chain alcohols, namely hexanol and heptanol, the conductivity remains very low up to a high water volume fraction. 

The plots between In <7 and T were obtained for these systems which produced good linear fits (Figure 5.13). values were calculated from the slopes and presented as function of water volume fraction for the microemulsions based on the two oils in Figure 5.14. Similar behaviors of were reported [99, 108-110], Five different regitms can be identified in the activation energy of conduction... 

FIGURE 9.3 (a) Specific conductance (K) as a function of the water volume fraction )... 

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