PEEKs selectivity/solubility

High proton conductivity (a) and low methanol permeability Pchsoh) are two of the essential characteristics that a polymer electrolyte membrane has to possess in order to be validly proposed for use in DMFC. Combining these two parameters into a factor defined selectivity (=log(o-/P)) [24], a comparison can be more easily carried out within different S-PEEK membranes. In Figure 11, the P factor comparison between a S-PEEK sample and Nafionl 17 membranes is shown. Increasing the DS, the S-PEEK s selectivity decreases because, overcome DS = 70%, the sulfonated polymer becomes more soluble in methanol and then methanol permeability increases [20]. 

Table 1.1 Comparison of predicted to experimental diffusion selectivities and solubility selectivities for (O2, N2) in selected PEEKs.

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