## Materials and Methods
### Membrane Characterizations  
The synthesis of the anion-exchange polymer was confirmed by FT-IR (FT/IR-4700, Jasco, Tokyo, Japan) analysis. The morphological characteristics of the porous substrates and prepared PFAEMs were investigated by employing field emission scanning electron microscopy (FE-SEM, TESCAN, Czech). The surface hydrophilicity of the membranes was also evaluated using a contact angle analyzer (Phoenix 150, SEO Co., Suwon-si, Korea). The water uptake (WU) of the membranes was determined using the following equation:  
\[\text{WU}\left(\%\right)=\left(\frac{W_{wet}-W_{dry}}{W_{dry}}\right)\times 100 \tag{1}\]  
where \(W_{dry}\) and \(W_{wet}\) are the dry and wet membrane weights, respectively. A traditional titration method was employed to determine the ion-exchange capacity (IEC) of the membranes. After the pre-equilibrium in 0.5 M NaCl, chloride ions in the membrane were fully exchanged with sulfate ions in 0.25 M Na\({}_{2}\)SO\({}_{4}\). The amount of Cl\({}^{-}\) was then quantitatively analyzed by titration with an AgNO\({}_{3}\) standard solution, and the IEC values were calculated using the following equation:  
\[\text{IEC}\left(\text{meq.}/\text{g}_{\text{dry\,memb}}\right)=\frac{N_{\text {Cl}^{-}}\cdot V_{s}}{W_{dry}} \tag{2}\]  
where \(N_{\text{Cl}^{-}}\) is the normal concentration of Cl\({}^{-}\) (meq/L), \(V_{s}\) is the solution volume (L), and \(W_{dry}\) is the dry membrane weights (g). Both the ion conductivity (\(\sigma\)) and electrical area resistance (EAR) of the membranes were evaluated in a 1.0 M KOH solution at room temperature using a lab-made clip cell and an LCZ meter. The \(\sigma\) values were obtained from the following equation:  
\[\sigma\left(\text{S}/\text{cm}\right)=\frac{l}{R_{memb}\cdot A} \tag{3}\]  
where \(R_{memb}\) is the resistance (\(\Omega\)), \(l\) is the thickness (cm), and \(A\) is the effective area (cm\({}^{2}\)) of the tested membrane. The EAR was estimated using the following equation:  
\[\text{EAR}\left(\Omega\text{ cm}^{2}\right)=\left(|Z|_{sample}\cdot cos\theta_{ \text{sample}}-|Z|_{blank}\cdot cos\theta_{\text{blank}}\right)\cdot A \tag{4}\]  
where \(|Z|\) is the magnitude of impedance (\(\Omega\)), \(\theta\) is the phase angle, and \(A\) is the effective area (cm\({}^{2}\)) of the tested membrane. The transport number (\(t_{-}\)) for counter ions (Cl\({}^{-}\)) was obtained by measuring the cell potential (=electromotive force, emf) using a two-compartment cell (membrane area = 0.785 cm\({}^{2}\), each volume = 0.23 dm\({}^{3}\)) equipped with a pair of Ag/AgCl reference electrodes. As a result, the \(t_{-}\) values were determined by the following equation:  
\[E_{m}=\frac{RT}{F}(1-2t_{-})\ln\frac{a_{L}}{a_{H}} \tag{5}\]  
where \(E_{m}\) is the cell potential, \(F\) the Faraday constant, \(T\) the absolute temperature, \(R\) the molar gas constant, and \(a_{H}\) and \(a_{L}\) the activity in high and low concentration compartments, respectively. The alkaline stability of the membranes was evaluated by conventional soaking tests under a harsh alkaline environment (1 M KOH; 60 \({}^{\circ}\)C; 500 h). The oxidative stability of the membranes was also checked by \begin{table}
\begin{tabular}{c c c c} \hline
**Substrate** & **Thickness (\(\mu\)m)** & **Pore Size (\(\mu\)m)** & **Porosity (\%)** \\ \hline Hydrophobic PTFE & & & \\ (T020A142C) & 80 & 0.2 & 74 \\ Hydrophilic PTFE & & & \\ (H020A142C) & 35 & 0.2 & 71 \\ \hline \end{tabular}
\end{table} 
Table 1: Specifications of two porous polytetrafluoroethylene (PTFE) substrates utilized for preparing pore-filled anion-exchange membranes (PFAEMs) in this work. soaking experiments using [PERSON]'s reagent (3% H\({}_{2}\)O\({}_{2}\) containing 2 ppm FeSO\({}_{4}\)) at 80 \({}^{\circ}\)C for 6 h. The time-course changes in the transport number and membrane weight were recorded to evaluate the alkaline and oxidative stabilities, respectively. The fuel (hydrazine, N\({}_{2}\)H\({}_{4}\)) crossover rates through the membranes were estimated via conventional 2-compartment diffusion cell tests.