## Materials and Methods
### Electrical Response Measurements  
Complex impedance spectroscopy, CIS (Agilent 4294A), was used in the frequency range of 40 Hz to 60 MHz to evaluate the electrical response of the samples to temperature and moisture changes, using a closed chamber with a volume of approximately 6.5 L. For that purpose, a pair of gold electrodes was printed through a mask onto the surface extremities of each membrane, using gold ink from the Gwent Group (Gold Polymer Electrode Paste C2041206P2) and heated afterwards up to 80 \({}^{\circ}\)C, for 60 min. Complex impedance data integrity validation was ensured using the Agilent equipment, because it has inbuilt Kramer-Kronig transformations. For each sample type, two specimens of each composition were characterized, for which three acquisition runs were performed in each measure, and the data displayed were always the mean values of the three runs for both specimens and for each measure.  
Electrical response evaluations to temperature were performed in dry air, with temperatures varying between 25 and 250 \({}^{\circ}\)C. For moisture electrical response evaluations, the measurements were performed at room temperature by varying the relative humidity (RH), from dry air, i.e., 0% RH, to fully humidified air, 100% RH. The different values of RH were obtained by mixing water-saturated air in the chosen ratio, obtained by bubbling synthetic air through water in a bubbler, with dry synthetic air. The volumetric flow rates of both saturated wet and dry air were controlled by independent mass flow controllers, and then joined together in a mixer before passing tangentially over the surface of the sensors placed inside the test chamber. The temperature inside the chamber was electronically controlled with an accuracy greater than 1 \({}^{\circ}\)C and maintained at 25 \({}^{\circ}\)C (ambient temperature). All the electrical measurements were performed with the samples subjected to a 5 L/h flow rate of a given mixture and maintained for at least 90 min.  
Electrical impedance was evaluated by applying an alternated current, AC, sinusoidal-current-shaped signal, and by measuring the obtained response, which was in an AC sinusoidal voltage signal containing its excitation frequency and harmonics. In addition, its usage, in place of a direct current signal, DC, avoids undesirable polarization phenomena. Electrical impedance measurements are normally performed using a small amplitude excitation signal in order to assure that the sample response is pseudo-linear. In a linear or pseudo-linear system, the AC response to a sinusoidal current signal will present the same frequency but will be phase-shifted. Generally, when a time-defined excitation current, \(I(t)=I_{DC}+I_{0}\exp(i\omega t)\), is applied to the medium, the corresponding measured voltage will have the form \(V(t)=V_{DC}+V_{0}\exp(i\omega t-i\omega)\). Therefore, from [PERSON]'s law, the overall impedance of the medium will be given by \(Z=\frac{V(t)}{I(t)}=\frac{V_{0}\exp(i\omega t)}{I_{0}\exp(i\omega t-i\omega)}\), where \(\omega\) stands for the angular frequency, \(I_{DC}\) represents the continuous component of the current signal, \(I_{0}\) is the maximum amplitude of the oscillating component of the current signal, \(V_{DC}\) is the continuous component of the voltage signal, and \(V_{0}\) is the maximum amplitude of the oscillating component of the voltage signal. However, and as stated above, the main benefits of using electrical impedance spectroscopy for the characterization of sample responses, arise while avoiding the appearance of polarization phenomena in the medium. Therefore, in the present study, the used excitation signal had no continuous component, and its respective voltage was measured as well: the latter could be confirmed by close inspection of the presented Nyquist plots, and consequently, the electrical equivalent circuit did not need to contain any element representative of any kind of DC component/contribution.