To prepare ion-exchange membrane from poly(vinyl alcohol) (PVA) and poly (sodium-4-styrene sulfonate) (PSSNa), the polymer compatibility was investigated by means of differential scanning calorimetry, attenuated total reflection Fourier Transform Infrared spectroscopy, and scanning electron microscopy. Using the strong-fragile concept to interpret the differential scanning calorimetric results, we show that the interactions between the segments of both polymers increase with decrease in PVA fraction. Because of these intermolecular interactions, the PVA crystallinity degree decreased with the decrease in PVA fraction, and a single-transition temperature was observed for the polymer blend in the amorphous phase. At the nanoscopic scale, the Fourier Transform Infrared results show that the PVA/PSSNa compatibility is mainly promoted by hydrogen bonds and dipole-ion interactions between PVA and PSSNa segments, whereas at microscopic scale, the morphology obtained by scanning electron microscopy technique shows that PVA and PSSNa form one homogeneous phase. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 2261-2269, 2009