The characterization results in Figure 6 affirms that the deposition of all the polycations significantly increased the hydraulic resistance of the PAN-A substrate, even though the deposited layer should have a negligible thickness of a few nanometers29. Moreover, the variation in the water permeability is consistent with the varying wettability characterized by their contact angles in Figure 5. That is, the relatively hydrophilic surface of the PAN-A substrate modified by PDADMAC yielded the highest water permeability, whereas the lowest water permeability corresponded to the hydrophobic surface resulting from the deposition of PAH.