## 3 Results and Discussion
This is one of the intrinsic characteristics of pore-filling types of membranes employing an inert porous substrate, that is, the hydrophobic nature of the porous substrate dominates the surface contact angles. The IEC values of the compared membranes were almost the same as each other, while the hydrophilic PFAEM revealed much higher conductivity for hydroxyl ions than those of both the hydrophobic-PFAEM and commercial membrane. As a result, the EAR of the hydrophilic-PFAEM was shown to be reduced by about four times compared with that of both the hydrophobic-PFAEM and the commercial membrane, because of the relatively high conductivity and thin membrane thickness. The prepared membranes exhibited excellent transport numbers for an anion (Cl\({}^{-}\)), which were superior to that of the commercial membrane. Moreover, the alkaline stability of the AEMs was also checked via soaking tests under a harsh alkaline condition (i.e., 1 M KOH/60 \({}^{\circ}\)C/500 h). The transport numbers of the AEMs were shown to be significantly reduced after the alkaline soaking tests. The decrement in the transport numbers could have mainly originated from the degradation of quaternary ammonium sites under a harsh alkaline environment. The decrease in the transport number of the PTFE-based PFAEMs was much smaller than that of the commercial membrane, demonstrating that both, the use of chemically stable PTFE substrates, and the highly cross-linked ionomer, could largely enhance the alkaline stability of the membranes. The oxidative stability of the commercial and prepared membranes was also evaluated with the soaking experiment, using [PERSON]'s reagent (3% H\({}_{2}\)O\({}_{2}\) containing 2 ppm FeSO\({}_{4}\)). As shown in Table 2 and Figure 5, the chemical stabilities of the PFAEMs were superior to that of the commercial membrane. The result demonstrates that the combination of a chemically stable PTFE substrate and a highly cross-linked hydrocarbon ionomer significantly enhances the chemical stability of the membranes. In addition, the differences in the chemical stability of the two PFAEMs were not that significant. The MEAs utilizing two different PFAEMs were evaluated by the _I-V_ polarization test, using a liquid fuel of 4 M KOH and 4 M N\({}_{2}\)H\({}_{4}\) at 60 \({}^{\circ}\)C and 100% RH. The _I-V_ and current-power (_I-P_) polarization curves of the MEAs are displayed in Figure 6. As a result, the power generation performance of the MEA was dramatically improved by employing the hydrophilic membrane instead of the hydrophobic one. The maximum power density of the MEA employing the hydrophilic-PFAEM was shown to be about 400 mW cm\({}^{-2}\) at 1 A cm\({}^{-2}\). This result is almost comparable with that of the state-of-the-art membranes such as the Tokuyama A901 [28]. Since the crossover of liquid fuel through a membrane largely affects the energy conversion efficiency in such types of fuel cell [44], we also evaluated the diffusion coefficients of N\({}_{2}\)H\({}_{4}\) through the PFAEMs, by means of conventional two-compartment diffusion cell tests. As shown in Table 3, the diffusion coefficient of the fuel molecule through the hydrophilic-PFAEM was revealed to be somewhat higher than that of the