Ionic cluster solution, partitioned

Figure 10. Hypothetical ionic cluster solution as partitioned into a fraction containing all the dissociated (and hydrated) ions and free water, and a fraction containing all the bound ( ) ( — ) pairs with their requisite water of hydration (24).

The preference of Nafion for up taking methanol over water is certainly an undesirable property for DMFC using this proton conducting membrane. It would be worth to review the effect of inorganic or organic Nafion composite membranes on the sorption of water-methanol from the liquid phase and on the partition constant. The few reported studies include Nafion/sulfonated organosilica [47] and Nafion/zirconium phosphate [78], where a reduction of the total liquid uptake is observed for the composites in methanol solutions up to 10 M, attributed to a reduction of the free volume in the ionic clusters. 

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